Tag Archives: evolution

These hard-bodied robots can reproduce, learn and evolve autonomously

Where biology and technology meet, evolutionary robotics is spawning automatons evolving in real-time and space. The basis of this field, evolutionary computing, sees robots possessing a virtual genome ‘mate’ to ‘reproduce’ improved offspring in response to complex, harsh environments.

Image credits: ARE.

Hard-bodied robots are now able to ‘give birth’

Robots have changed a lot over the past 30 years, already capable of replacing their human counterparts in some cases — in many ways, robots are already the backbone of commerce and industry. Performing a flurry of jobs and roles, they have been miniaturized, mounted, and molded into mammoth proportions to achieve feats way beyond human abilities. But what happens when unstable situations or environments call for robots never seen on earth before?

For instance, we may need robots to clean up a nuclear meltdown deemed unsafe for humans, explore an asteroid in orbit or terraform a distant planet. So how would we go about that?

Scientists could guess what the robot may need to do, running untold computer simulations based on realistic scenarios that the robot could be faced with. Then, armed with the results from the simulations, they can send the bots hurtling into uncharted darkness aboard a hundred-billion dollar machine, keeping their fingers crossed that their rigid designs will hold up for as long as needed.

But what if there was a is a better alternative? What if there was a type of artificial intelligence that could take lessons from evolution to generate robots that can adapt to their environment? It sounds like something from a sci-fi novel — but it’s exactly what a multi-institutional team in the UK is currently doing in a project called Autonomous Robot Evolution (ARE).

Remarkably, they’ve already created robots that can ‘mate’ and ‘reproduce’ progeny with no human input. What’s more, using the evolutionary theory of variation and selection, these robots can optimize their descendants depending on a set of activities over generations. If viable, this would be a way to produce robots that can autonomously adapt to unpredictable environments – their extended mechanical family changing along with their volatile surroundings.

“Robot evolution provides endless possibilities to tweak the system,” says evolutionary ecologist and ARE team member Jacintha Ellers. “We can come up with novel types of creatures and see how they perform under different selection pressures.” Offering a way to explore evolutionary principles to set up an almost infinite number of “what if” questions.

What is evolutionary computation?

In computer science, evolutionary computation is a set of laborious algorithms inspired by biological evolution where candidate solutions are generated and constantly “evolved”. Each new generation removes less desired solutions, introducing small adaptive changes or mutations to produce a cyber version of survival of the fittest. It’s a way to mimic biological evolution, resulting in the best version of the robot for its current role and environment.

Virtual robot. Image credits: ARE.

Evolutionary robotics begins at ARE in a facility dubbed the EvoSphere, where newly assembled baby robots download an artificial genetic code that defines their bodies and brains. This is where two-parent robots come together to mingle virtual genomes to create improved young, incorporating both their genetic codes.

The newly evolved offspring is built autonomously via a 3D printer, after which a mechanical assembly arm translating the inherited virtual genomic code selects and attaches the specified sensors and means of locomotion from a bank of pre-built components. Finally, the artificial system wires up a Raspberry Pi computer acting as a brain to the sensors and motors – software is then downloaded from both parents to represent the evolved brain.

1. Artificial intelligence teaches newborn robots how to control their bodies

Newborns undergo brain development and learning to fine-tune their motor control in most animal species. This process is even more intense for these robotic infants due to breeding between different species. For example, a parent with wheels might procreate with another possessing a jointed leg, resulting in offspring with both types of locomotion.

But, the inherited brain may struggle to control the new body, so an algorithm is run as part of the learning stage to refine the brain over a few trials in a simplified environment. If the synthetic babies can master their new bodies, they can proceed to the next phase: testing.

2. Selection of the fittest- who can reproduce?

A specially built inert nuclear reactor housing is used by ARE for testing where young robots must identify and clear radioactive waste while avoiding various obstacles. After completing the task, the system scores each robot according to its performance which it then uses to determine who will be permitted to reproduce.

Real robot. Image credits: ARE.

Software simulating reproduction then takes the virtual DNA of two parents and performs genetic recombination and mutation to generate a new robot, completing the ‘circuit of life.’ Parent robots can either remain in the population, have more children, or be recycled.

Evolutionary roboticist and ARE researcher Guszti Eiben says this sped up evolution works as: “Robotic experiments can be conducted under controllable conditions and validated over many repetitions, something that is hard to achieve when working with biological organisms.”

3. Real-world robots can also mate in alternative cyberworlds

In her article for the New Scientist, Emma Hart, ARE member and professor of computational intelligence at Edinburgh Napier University, writes that by “working with real robots rather than simulations, we eliminate any reality gap. However, printing and assembling each new machine takes about 4 hours, depending on the complexity of its skeleton, so limits the speed at which a population can evolve. To address this drawback, we also study evolution in a parallel, virtual world.”

This parallel universe entails the creation of a digital version of every mechanical infant in a simulator once mating has occurred, which enables the ARE researchers to build and test new designs within seconds, identifying those that look workable.

Their cyber genomes can then be prioritized for fabrication into real-world robots, allowing virtual and physical robots to breed with each other, adding to the real-life gene pool created by the mating of two material automatons.

The dangers of self-evolving robots – how can we stay safe?

A robot fabricator. Image credits: ARE.

Even though this program is brimming with potential, Professor Hart cautions that progress is slow, and furthermore, there are long-term risks to the approach.

“In principle, the potential opportunities are great, but we also run the risk that things might get out of control, creating robots with unintended behaviors that could cause damage or even harm humans,” Hart says.

“We need to think about this now, while the technology is still being developed. Limiting the availability of materials from which to fabricate new robots provides one safeguard.” Therefore: “We could also anticipate unwanted behaviors by continually monitoring the evolved robots, then using that information to build analytical models to predict future problems. The most obvious and effective solution is to use a centralized reproduction system with a human overseer equipped with a kill switch.”

A world made better by robots evolving alongside us

Despite these concerns, she counters that even though some applications, such as interstellar travel, may seem years off, the ARE system may have a more immediate need. And as climate change reaches dangerous proportions, it is clear that robot manufacturers need to become greener. She proposes that they could reduce their ecological footprint by using the system to build novel robots from sustainable materials that operate at low energy levels and are easily repaired and recycled. 

Hart concludes that these divergent progeny probably won’t look anything like the robots we see around us today, but that is where artificial evolution can help. Unrestrained by human cognition, computerized evolution can generate creative solutions we cannot even conceive of yet.

And it would appear these machines will now evolve us even further as we step back and hand them the reins of their own virtual lives. How this will affect the human race remains to be seen.

Invasive cannibalistic toads are evolving so fast they’re pushing the limits of evolution

For cane toads in Australia, the biggest enemy is often… other cane toads. Cannibalistic tadpoles often munch on hatchlings like it’s an eating contest, and they do it so much they’re pushing the hatchlings into developing quicker — but this comes at a cost.

Invasive species are known for their ability to achieve high densities within their introduced range, the researchers note. Image in public domain.

It had to be Australia

The first cane toads (about 100 or so) were brought to Australia in 1935, in an attempt to control the cane beetles that had been running rampant through the plantations. Not only did the toads not eliminate the beetles, but they became a problematic invasive species themselves, multiplying way beyond control.

It’s a sad story that Australia went through multiple times, with different animals. Because they are poisonous, the cane toads (Rhinella marina) have no natural predators, and went on to grow and spread throughout large swaths of the country. To make things even worse, carnivorous marsupials in Australia can mistake the toads as their prey, falling victim to the toxin.

But although adult toads can be quite menacing (measuring 25 cm, or 10 inches long), it’s their tadpoles that are carnivorous (at least most of the time).

It’s not that uncommon for tadpoles to become cannibalistic, many frog and toad species do it. Normally, they only get snippy and try to eat their relatives in the pond when resources are scarce. But in the case of the Australian cane toads, this seems to be happening a lot.

A single clutch can have thousands or even tens of thousands of eggs. The tadpoles that hatch earlier can then gobble up the unhatched eggs — and they do it like there’s no tomorrow. Researchers have documented cases where over 99% of the hatchlings in a clutch were consumed by just a few tadpoles.

Jayna DeVore, an invasive-species biologist at Tetiaroa Society, a non-profit organization in French Polynesia, wanted to see whether all cane toads do this or just the Australian invaders. Along with her colleagues, she carried out a few experiments.

In one such experiment, repeated 500 times with different individuals, the researchers placed a tadpole in a container with 10 hatchlings. They found that all tadpoles engage in some cannibalism but hatchlings were “2.6 times as likely to be cannibalized if that tadpole was from Australia.”

In another experiment, tadpoles from invasive toads were much more attracted to hatchlings than non-Australian ones. The researchers placed two traps, one that was empty and one that held hatchlings. The Australian tadpoles were 30 times more attracted to the hatchlings than the other ones.

An arms race

Tadpoles from another species (Agalychnis callidryas). Image credits: B. Kimmel / Wiki Commons.

Of course, the hatchlings aren’t sitting still. Well, they are, in a pond, but they’re not still in an evolutionary perspective.

Hatchlings in Australia are developing at a much faster pace than the others. This comes at a cost — when they reach the tadpole and mature stages of their life, they will not be as well-developed as their non-Australian peers, but it beats being devoured by a tadpole.

Even more impressively, the hatchlings seem to speed up the pace of their development when they sense a chemical released by other tadpoles. Since it’s not worth developing quicker when there’s no risk of cannibalism, the hatchlings only do it when they sense a risk.

“Here, we find that toad tadpoles from invasive Australian populations have evolved both a strong behavioral attraction to the vulnerable hatchling stage and an increased propensity to cannibalize these younger conspecifics. In response, these toads have also evolved multiple strategies for reducing the duration of the vulnerable period, indicating an evolutionary arms race between the cannibalistic tadpole stage and the vulnerable egg and hatchling stages in invaded habitats,” the researchers note in the study.

Although cannibalism is generally a dangerous strategy, in the case of the cane toads, it could actually be helpful. Tadpoles that consume their relatives aren’t just getting a lot of nutrients — they’re eliminating competition for the pond resources, which are sometimes scarce. They develop to mature toad stage faster and tend to be larger.

But the good news is that at the very least, this works as a form of population control, limiting the spread of the invasive species.

It’s also a remarkable demonstration of how fast evolution can trigger changes. The toads roaming Australia now are notably different from those who first stepped foot on the continent. Australian cane toads are a frightening bunch: not only are they cannibalistic invaders, but they’re also evolving at a very rapid pace.

The study was published in PNAS.

Scientists make the smallest-ever man-made flying devices inspired by propeller seeds

A microflier next to an ant for scale. Credit: Northwestern University.

There’s something mesmerizing about the elegant whirling motion of the maple’s leaf propeller seed spinning through the air before it gently touches the ground. This is not just some romantic autumn scenery, though. Although trees are static they can disperse over relatively vast distances on their own by evolving these sort of sophisticated, aerodynamic seeds. Inspired by nature, scientists have now borrowed the maple seed design, as well as others, to give microchips wings.

These amazing microfliers are about the size of a grain of sand, but despite their tiny size they pack enough electronics and sensors to monitor their surroundings, store data, and communicate wirelessly. And thanks to their design, these fidget-spinner-like devices can fly like a helicopter without a motor or engine.

The Northwestern University team of engineers behind this remarkable project believes a swarm of these microfliers could prove highly useful for an array of applications, whether it’s scouring the atmosphere for pathogens or particle pollution.

“We have long-standing research interests in ultra-miniaturized electronics and sensors for the human body – as an extension, we began to think about uses of adapted versions of those devices for monitoring the environment.  A key challenge in that context is in distributing large, wireless collections of such devices over large areas and designing them in a way to maximize their interactions with the environment (e.g. the atmosphere for pathogens and/or particulate pollution).  Active flying capabilities might be interesting in this context, but passive schemes like those used by plants and trees, as bioinspired ideas, are particularly attractive due to simplicity,” John A. Rogers, Professor of Materials Science and Engineering, Biomedical Engineering and Neurological Surgery at Northwestern, told ZME Science.

Better than nature’s design

A 3D microflier (right) compared to a tristellateia seed in free fall. Credit: Northwestern University.

Propeller seeds employed by some tree species evolved over hundreds of millions of years. Over time, the most adapted seed designs that interacted with wind patterns for the longest possible period of time took over and became the norm.

When you encounter a design that has been tried and tested over millions of years, it’s easy to see why Rogers and colleagues jumped onboard. But they didn’t merely copy these designs — they tweaked and built upon them, eventually surpassing nature.

After studying the aerodynamics of numerous types of plant seeds, the researchers were most impressed by the star-shaped seeds of the tristellateia plant, a flowering vine. Using this design as a starting point, the engineers devised various microflier versions, including one with three wings whose shape and angles are similar to the tristellateia seed.

A close-up of a 3D microflier, outfitted with a coil antenna and UV sensors. Credit: Northwestern University.

These designs were polished even further after they went through a battery of tests using both computational methods and empirical measurements of airflow. The end result is a super-advanced microflier that is capable of falling with more stable trajectories and a slower velocity than similar propelled seeds found in nature.

“Forming the 3D collection of wings in ways and with materials that naturally integrate with millimeter-scale electronic systems was a key challenge.  We were quite pleased to find that we could not only make and optimize the structures, but that their performance could exceed that of naturally occurring seeds with sizes that are far smaller,” Rogers proudly recounted.

To demonstrate the abilities of these microfliers, the Northwestern scientists embedded sensors, a power source that harvests energy from the wind, memory storage, and an antenna for wireless transfer of data to third-party devices — all within a one-millimeter frame, wings included.

Some microfliers were fitted with sensors that detect particle pollution in the air, others had pH sensors that are useful for monitoring water quality or photodetectors that measure different wavelengths of sunlight.

“Seeds” that monitor the environment

A swarm of these could be dropped from a high or low altitude, depending on how large the surface area of interest for monitoring is. “We envision areas that might range from a fraction of a square mile to several square miles,” Rogers said. They could be used routinely to monitor the environment or during emergency situations, such as a chemical spill to quickly assess the damage.

Unlike traditional monitoring instruments, having hundreds or thousands of these microfliers covering an area could provide much more granular data with a very high spatial density. On the other hand, that sounds like a lot of litter — but the scientists thought ahead, though.

When deployed in the field, the researchers plan on using microfliers made from degradable polymers and dissolvable integrated circuits that safely dissolve in water. So essentially, after the tiny devices finish their mission, they should seamlessly disintegrate into the environment.

This is just the beginning though. Just like nature fostered multiple designs adapted for various environments and purposes, so do the researchers plan on working on new microflier versions.

“We are working on sensors for biological species – pathogens, bacteria, etc – and for heavy metal contaminants.  Advanced wireless electronics, power supply strategies and so on will also be important.  As a longer-term goal, active, flapping fliers could be interesting.  We are also exploring different types of seed designs – parachuters, flutterers, gliders, etc – and we are now demonstrating environmentally degradable electronic sensors as payloads,” Rogers said. 

Not so picky and coy after all: Female animals also have mating contests. They’re just more subtle than males

Sage-grouse on lek site in Central Oregon. Credit: NRCS Oregon, Flickr.

Men chase and women choose. This old-fashioned perspective on dating is also surprisingly prevalent among scientists studying mating dynamics shaped by sexual selection, wherein male animals are seen as more expendable and have to compete for the attention of picky females. But a new study shines light on the often-overlooked female competition for access to quality male mates, showing that sexual selection in females is actually the norm rather than the exception.

Victorian-era sex stereotypes

Charles Darwin claimed that all living species were derived from common ancestors, proposing natural selection as the driving mechanism in his pivotal book On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. Natural selection says that organisms better adapted to their environment would benefit from higher rates of survival than those less equipped to do so, and would thus be more likely to pass on copies of their genes.

Darwin noted, however, that some elaborate traits had no apparent adaptive purpose and clearly did not aid survival (and in some cases jeopardized it by attracting predators) but rather served a sexual purpose. The male peacock with its extravagant plumage is an often-cited example of this effect. These traits could evolve if they are sexually selected, hence the name sexual selection, which Darwin explored at length in his follow-up book, The Descent of Man.

Sexual selection operates through two mechanisms: intrasexual selection, which refers to competition between members of the same sex (usually males) for access to mates, and intersexual selection, where members of one sex (usually females) choose members of the opposite sex. 

In a new study, a team of researchers led by Salomé Fromonteil of CNRS and the University of Rennes in France argues that the male-centered perspective on sexual selection is greatly exaggerated and has contributed to “a pervasive bias in research agendas of behavioural ecologists and evolutionary biologists over the last decades.

“Despite an increased awareness that females also compete for mating partners, we still tend to consider sexual selection in females a rare peculiarity,” the researchers wrote in a new study that appeared in the preprint server biorxiv.org.

In the 19th-century, Darwin wrote in his original conception of sexual selection that “with almost all animals, in which the sexes are separate, there is a constantly recurrent struggle between the males for the possession of the females” and that “the female […], with the rarest exception, is less eager than the male […,] she is coy and may often be seen endeavouring for a long time to escape from the male.”

This Victorian-era assertion has proven remarkably resilient, largely because there is some truth to it. In 2016, Tim Janicke, an evolutionary biologist at the University of Montpellier in France and co-author of the new study, measured the strength of sexual selection acting upon a variety of animal species and found that males experience a higher degree of sexual selection than females do.

However, the male side of sexual selection is greatly inflated compared to the female side, the researchers argue. For instance, studies exploring aspects of sexual selection on males outnumber those examining female competition for mates and male choice by a factor of ten to one, despite the fact that there are numerous instances of female intrasexual selection in the animal kingdom.

When females compete for males’ attention

Seahorses mating, taken at Seahorse World in Beauty Point, Tasmania. Credit: Flickr, John Dalton.

The clearest examples can be found in so-called sex-role reversed species in which the females actively compete for males and are the more ornamented sex. These include pipefishes and seahorses, in which fertilization takes place inside the brood pouch of the male until the young are ready to hatch, and this male will provide all parental care. In such species, males are a limited resource for which females have to compete, which leads to selection for ornaments favored by males in both pre- and post-copulatory mate choice.

However, nature doesn’t have to be flipped on its head in order to see sexual selection operating in females. Even in species with conventional sex roles where male ornamentation and extravagant courtship behaviors are selected for, you can still see female competition for high-quality males. For instance, female wattled jacanas (Jacana jacana) are known to aggressively fight for control over territory in order to monopolize multiple mates. Meanwhile, dung beetle females have evolved small horns that they sometimes use to battle other females in contests over access to mates. In Black grouse (Tetrao tetrix), both males and females compete for mates in elaborate courtship displayed arenas called leks.

“Consequently, sexual selection in females might actually be an omnipresent phenomenon in animals but operating less intensely and more subtly compared to males, which can make it more difficult to detect,” the researchers wrote.

In their new investigation, Janicke and Fromonteil investigate the published literature reporting evidence of sexual selection in females from 72 species. Particularly, the researchers measured and compared the Bateman gradient, a measure of the fitness benefit of mating, named after 20th-century British geneticist Angus John Bateman.

Bateman’s work showed that males produce sperm at a low energy cost, whereas females have a relatively much higher investment in far fewer eggs. This energy imbalance in gamete investment, Bateman argued, drives competing strategies in males and females. Males are thus incentivized to spread their sperm to as many mates as possible and to compete with other males for access to mating partners, while females are incentivized to be more choosy.

Sex is costly for females but the worst outcome is no sex at all

The Bateman gradient is a measure of the benefit of having multiple mating partners. The steeper the curve of the Bateman gradient, the greater the fitness benefit a male or female gains from mating more.

Although these gradients varied wildly among the species included in the meta-analysis, the researchers found that females from species that had access to many partners had higher Bateman gradient values than females of species that tended to mostly mate with one male at a time.

In effect, this means that, just like males, females also gain a fitness boost from access to multiple males, which naturally opens the door for sexual selection. In fact, the study’s authors claim that sexual selection in females is the norm rather than the exception across the animal tree of life.

“Specifically, our results document that females – just as widely assumed for males – typically benefit from having more than one mating partner. As a consequence, selection is also expected to favour the evolution of female traits that promote the acquisition of mating partners. However, given the previously documented higher benefit of mating in males, sexual selection on females may often operate more hiddenly leading to the evolution of less conspicuous ornaments and armaments compared to males,” they wrote.

While the relative difference in gamete cost between the sexes likely drives important behavioral changes in their mating strategies, the researchers argue that reproductive success may sometimes be maximized when mating with multiple mates or, at the very least, having additional mating episodes.

“Collectively, our study contributes to a more nuanced view on sexual selection and sex differences in general. Darwinian sex roles may predominate the animal tree of life in the sense that sexual selection is typically stronger on males compared to females but our meta-analysis questions the view that females are typically coy and passive. Sexual selection on females should not be considered a rare phenomenon but instead be acknowledged as widespread across animals,” the researchers concluded.

Why mice have the potential to become as venomous as a viper

Credit: Pixabay.

Researchers have investigated the origins of one of the most highly specialized straits in the animal kingdom: oral venom. Unexpectedly, the researchers found that the basic genetic machinery is present in both mammals and reptiles. Specifically, there’s a molecular link between a venomous snake’s venom glands and a mammal’s salivary glands. In theory, if there’s pressure from natural selection, mice could potentially become venomous as well.

“This represents an ancient molecular framework that was likely already established in the ancestors of snakes and mammals. Mammals took a less complicated route and developed simple salivary glands while snakes diversified this system extensively to form the oral venom system. This allowed us to propose a unified model of venom evolution, namely that venoms across lizards and snakes evolved by taking advantage of existing genes in the salivary glands of their ancestors,” Agneesh Barua, a Ph.D. student at the Okinawa Institute of Science and Technology Graduate University (OIST) and lead author of the new study, told ZME Science.

Venom can be defined as a mixture of toxic molecules (“toxins”, which are mostly proteins) that one organism delivers to another (e.g. by a bite or a sting) for the purpose of defending itself, securing a meal, or deterring a competitor. Many different types of creatures — jellyfish, spiders, scorpions, snakes, and even some mammals — seem to have independently evolved venom. This had some scientists wondering whether venom actually evolved from non-venomous but related biological components inherited from a common ancestor. This couldn’t be proved — until now.

Researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) in Japan and the Australian National University carefully assessed thousands of genes related to venom. Previously, scientists had focused on genes that express the toxic proteins found in venom. But Barua and colleagues took it a step further and cast a wider net so they could identify genes that were likely present before the venom system evolved.

To this aim, they used venom glands harvested from the Taiwan habu snake (Protobothrops mucrosquamatus), a pit viper that’s indigenous to Okinawa.

“We have been trying to understand how non-venomous animals evolved venom for a long time. But, this was difficult to do because venoms evolve rapidly and the ancestral state gets difficult to reconstruct with great accuracy. We worked around that by focusing not on the toxins themselves, but on the machinery that makes them, which turned out to be highly conserved,” the researcher said.

More than 3,000 “cooperating” genes were identified that interact in some way or form with venom genes. Some protected the host cells from stress caused by producing lots of toxic proteins, while others regulated protein modification and folding. This is actually extremely important because misfolded proteins can accumulate and damage cells.

“This makes perfect sense because venoms are a cocktail of toxin proteins. It is vital that the protein structure of these toxins is maintained, otherwise, the venom won’t work, and the animal would not be able to catch its prey,” Barua said.

The surprising part was when the researchers looked at the genomes of other animals, including those you’d never think to connect with a venomous creature, such as dogs, chimpanzees, or humans, and found that they contained their own versions of these genes. When they realized that venom genes were actually co-expressed together and with a relatively small number of other genes, this was a “striking moment” for the researchers.

“This suggests that there is a common molecular framework between venom glands in snakes and salivary tissue in non-venomous mammals. This represents an ancient molecular framework that was likely already established in the ancestors of snakes and mammals. Mammals took a less complicated route and developed simple salivary glands while snakes diversified this system extensively to form the oral venom system. This allowed us to propose a unified model of venom evolution, namely that venoms across lizards and snakes evolved by taking advantage of existing genes in the salivary glands of their ancestors,” Barua added.

The study suggests that salivary gland tissues within mammals were expressed by genes that had a similar pattern of activity to that seen in venomous snakes, so genes for salivary glands and venom glands must share an ancient functional core. After the two lineages split hundreds of millions of years ago, the venomous species evolved biological systems that produced toxins, the authors note.

Bearing all of this in mind, it’s not all that surprising that over a dozen species of mammals are actually venomous. These include Eulipotyphla (solenodons and some shrews), Monotremata (platypus), Chiroptera (vampire bats), and Primates (slow and pygmy slow lorises).

Theoretically, this means that virtually any species of mammal could potentially become venomous with enough prodding from natural selection.

“Humans will never develop venom. But there is a distinct possibility in other mammals. For example, suppose there is a genetic mutation in a few individuals of some species of wild mice that allows them to catch more insects. These individuals will be able to procure more food and thus have ‘higher fitness’. This could lead them to out-compete their peers in terms of mating (or just general well-being) and thereby produce more offsprings that will carry the beneficial mutation. Now imagine this happening for several generations. There will come a time when populations of these newly formed venomous mice could drive the non-venomous ones extinct, thereby firmly establishing the venom character in the gene pool,” Barua wrote in an e-mail.

“We would like to try evolving venomous mice in the laboratory. It would be a practical test of the mechanisms we hypothesise in the paper, and potentially provide clues about why venom doesn’t evolve more often.”

In the future, the team of researchers plans on further exploring the genetic regulatory network that underlies venom gland evolution.

“One question is — how does venom evolution modify this network? We’re planning a couple of different studies on this front. One is to look across species that have evolved venom, including other reptiles and mammals. Are there commonalities in these two lineages?”

“One of the main scepticisms regarding the idea of evolution is that of ‘intelligent design.’ Proponents of this idea validate it by citing examples where scientists have not been able to completely decipher the origin of highly specialised traits. Scientists have quite a good idea of how traits originate, but direct mechanistic explanations are rare owing to the incredible genetic complexity of traits. We provide a mechanistic explanation of one of the most specialised traits in nature, oral venoms. Our study, therefore, provides a firm argument for evolution and can provide people will the proof they need to denounce pseudoscientific claims like intelligent design,” Barua said.

The findings appeared in the Proceedings of the National Academy of Sciences.

Book Review: ‘A Most Interesting Problem’

A Most Interesting Problem: What Darwin’s Descent of Man got Right and Wrong About Human Evolution
Edited by Jeremy DeSilva
Princeton University Press, 288 pages | Buy on Amazon

In 1859, Charles Darwin published what’s arguably the most influential book in modern science: On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life. In this seminal work, Darwin introduced the concept of natural selection — a cornerstone of modern biology — as a mechanism for evolution.

The British naturalist defined evolution as “descent with modification,” by which he meant species change over time, give rise to new species, and share a common ancestor. Organisms with heritable traits that favor survival and reproduction will tend to be more successful and produce more offspring than their peers, causing the traits to increase in frequency over generations — this is the crux of natural selection.

Unsurprisingly, these views, which we now hold for granted, were met with great backlash by Darwin’s peers and Victorian society at large. Although Darwin never addresses the question of human evolution in On the Origins of Species, the implications were obvious. If all species descend with modification, that means humans also descended from a lesser form, which was incongruent with creationist views of the time.

Darwin avoided addressing human evolution on purpose because he needed more time to construct his thesis, being well aware that was a sensitive topic. In 1871, the scientist finally published his follow-up The Descent of Man, in which he attempted to explain human evolution during a time when there were no confirmed fossil records of human ancestors.

What Darwin got right, and what he didn’t

In the book, Darwin prefaced this topic as “the highest and most interesting problem for the naturalist.” On this note, in the newly released A Most Interesting Problem, acclaimed scientists present what Darwin got right and what he got horribly wrong about the origin, history, and biological variation of humans 150 years after he wrote his thesis on human evolution.

The book is edited by Jeremy DeSilva, associate professor of anthropology at Dartmouth College, and features contributions from world-renowned experts in their field. Each chapter is authored by a different researcher discussing modern evidence supporting or countering Darwin’s views.

Unsurprisingly for a scientist of his magnitude with a phenomenal intuition of the natural world, Darwin was spot on with many of his assertions. For instance, his comparative study of living primates led him to claim that humans must have evolved in Africa, which is also .

He also made claims that have now been proven flat out wrong. His most obvious blunders were related to matters of race and sex. Darwin asserted that humans are separated into biological races that follow a hierarchy and that women were biologically inferior to men virtually in every way. Later, these views would be exploited by proponents of eugenics and white-supremacists in the 20th century.

That being said, it’s easy to judge Darwin’s by today’s standards. But during his time, Darwin was no more sexist or racist than his Victorian peers — that was simply the unfortunate status quo.

One can only wonder how the British naturalist must have reacted in the face of confounding evidence. My guess is that he would live by his scientific creed and renounce his previous claims in favor of those supported by evidence such as DNA, brain scans, and the fossils belonging to more than 60 hominins.

Ultimately, A Most Interesting Problem is a fantastic run-down of today’s understanding of human evolution and a great showcase of the scientific process. Science isn’t meant to be perfect, but its self-correcting nature makes it the best tool at our disposal for approximating reality.

The trap-jaw is the fastest in the world — and it independently evolved several times in ants

Trap-jaw ants are infamous for having one of the strongest bites among all animals, but we didn’t really understand how they evolved from more traditional jaws. A new study looking at their evolutionary history found that the distinctive mechanism behind trap-jaws has evolved independently several times across the globe.

Unlike normal gripping jaws, which open and close through the contraction of muscles, trap-jaws use a complex mechanism to latch themselves open and clamp down when needed. This mechanism allows the jaws to store energy much like a spring, and this can be released to produce a lot of force quickly.

Bit bite

“One of the central questions in biology is: how does something complex arise from something simple?” said Professor Economo, who leads the Biodiversity and Biocomplexity Unit at the Okinawa Institute of Science and Technology Graduate University (OIST).

“Structures like the trap-jaw depend on multiple interacting parts to function correctly. At first it can be hard to see how such complexity can arise through the gradual stepwise changes of evolution. Nevertheless, when we look closely biologists can uncover evolutionary pathways to complexity.”

A new study led by Professor Economo and Dr. Douglas Booher from Yale University tracked the evolutionary history of trap-jaws, finding that they evolved independently, on several occasions, around the globe. Many of the species that sport such jaws come from the Strumigenys genus, which includes over 900 species found in tropical and subtropical regions.

For the study, the team sequenced the genetic information of 470 species in this genus recovered from all around the globe, including two types of gripping jaws (ancestral and with modified trap-jaws). From this, they reconstructed their family tree, which shows how different species are related.

Finally, they analyzed the jaws and ants themselves using micro-CT scanners, allowing them to create 3D models.

One of the first observations the team made was that only minor changes in structure were required to turn a gripping jaw into a trap-jaw. They further report that after this transition took place, the heads of (now trap-jawed) ants also started to morph quite dramatically. Muscle restructuring and changes in the length and open-width of the jaws were among the key changes.

“Previously, we had thought that all trap-jaws had both divergent form and divergent function, so it was much less obvious as to whether the change in function could occur at the start or whether a lot of changes to the form were first needed as a precondition,” said Professor Economo.

“But it turned out there are many intermediate forms out there of the trap-jaw mechanism that people just hadn’t identified before, some which differ only slightly from the ancestral form.”

In a collaboration with the lab of Andrew Suarez at the University of Illinois, the team also used high-speed video cameras to capture the jaws of Strumigenys ants in motion. They were thus able to determine that the trap-jaws have the fastest yet “acceleration of any animal body part that can return to its original position”. Such jaws were seen to accelerate a hundred times faster than standard mandibles, closing a thousand times faster than a human eye can blink. Which sounds impressively fast.

But they need all the speed they can get. Strumigenys ants use their jaws to capture springtails, their preferred prey, which employ a spring-loaded escape mechanism (hence the name). There’s still a lot we don’t understand about their hunting habits, but we do know that ants with shorter trap-jaws tend to be passive hunters, hiding in leaf litter with open jaws, waiting to bite down on any prey passing by. Longer-jawed ants, meanwhile, actively look for prey to bite into.

Both types of ants can be found in every region across the globe, the authors add. They believe that differences in behavior can explain why there are so many different shapes of trap-jaws out there. However, what is yet unclear is whether the genetic background that supported the change from normal- to trap-jaws is the same for all species, or whether they all reached the same solution through different genetic changes.

“It was really striking how we saw the same variations evolve again and again on different continents. It illustrates how repeatable evolution can be, finding similar solutions to life’s challenges,” said Professor Economo.

Going forward, the team plans to sequence the genomes of representative Strumigenys species across the world in order to determine this.

The paper “Functional innovation promotes diversification of form in the evolution of an ultrafast trap-jaw mechanism in ants” has been published in the journal PLOS Biology.

Global warming is faster than evolution — and this could spell trouble for marine life

Zebrafish (Danio rerio). Credit: Per Harald Olsen, NTNU.

The climate is always changing, say some skeptics who downplay the urgency and impact of anthropogenic global warming. What they miss is that natural climate change occurs over a much broader timeline, which typically allows species to evolve and adapt to their new environment. The only exceptions are during mass extinctions, and some scientists not only believe that today’s climate change is unnatural, but that it’s representative of a new mass extinction, the sixth one since complex life appeared on Earth.

Case in point, a new study performed the largest artificial evolution experiment on warming tolerance, showing that the rate of global warming is faster than the rate of evolution in zebrafish. For other slow-breeding animals, global warming may actually be even faster than their innate capacity to adapt.

“The question of evolutionary rescue to climate change impacts is extremely important but very difficult to answer, and we realised that a large artificial selection experiment would be a good start to attempt to get those answers. We managed to see evolution of higher thermal tolerance in fish in the lab, which is amazing in itself. Unfortunately, the rate of evolution we measured is slower than what would have been needed for successful adaptation to climate change,” Fredrik Jutfelt, associate professor at the Norwegian University of Science and Technology’s (NTNU) Department of Biology, told ZME Science.

Left behind to perish in a world that changes too fast

In order to investigate how zebrafish (Danio rerio) cope and adapt to rising water temperature, Jutfelt and colleagues contrived a huge experiment involving more than 20,000 individuals bred over six generations. The original fish were caught in the wild and then bred by the researchers based on their ability to withstand water of increasing temperature.

The experiments last for three years, during which the researchers were most concerned with preserving the health of fish. Any infection or system failure of the aquarium would have been catastrophic to the study, but luckily the research was completed without any such problems.

The work was tedious nevertheless, as the researchers had to follow thousands of individuals and measure their thermal tolerance. Only those who were in the top third performers were allowed to reproduce the next generation.

“Using this method over generations we can measure the response to selection and the rate of evolutionary change. Simple in theory but requires a lot of work when dealing with larger organisms,” Jutfelt said.

Reseachers in Norway performed the lagest artificial evolution experiment in history. From left to right: Mette Finnøen, Fredrik Jutfelt, Gunnar Dresler, Rachael Morgan and Josefin Sundin. Credit: Harald Olsen, NTNU.

According to the results, this artificial evolution increased heat tolerance in the fish by just 0.04 °C per generation. For many species, especially those with long breeding cycles, this is much slower than the rate of warming experienced in their environment.

“Generation time has a huge impact on the evolutionary potential. Some tiny animals have generation times of days or weeks, which means they have the potential to rapidly adapt to environmental changes. Greenland sharks, for example, become reproductive at around 150 years old, so evolution takes millennia. Our study suggests that even fishes with short generation times such as zebrafish will struggle to adapt rapidly enough as the waters warm,” Jutfelt said.

The vast majority of global warming (over 90%) is absorbed by the oceans, which act as planetary heat sinks. As a result, the world’s oceans were 0.77 °C warmer in 2019 compared to the average for the 20th century — and this warming has been accelerating. A study published in the journal Advances in Atmospheric Sciences early this year showed that the rate of warming in the oceans has increased by 450% in the last three decades compared to the preceding three decades.

In response, marine species have been forced to change their habits and breeding patterns, as well as to migrate towards the poles, much faster than land animals. Above a threshold, there will simply be no place to hide, and many species of fish and other marine wildlife will perish.

Scientists have known all along that species cannot possibly keep up with the accelerating ocean temperatures, but this new study has finally quantified just how much the evolution of marine species may be lagging behind. Although zebrafish are freshwater fish, marine fish with similar breeding cycles may respond similarly.

In the future, Jutfelt and colleagues plan on investigating the mechanisms, both physiological and genetic, that allowed the zebrafish to adapt to warming.

“Many have hoped that animals can adapt to warming, to change in concert with the increasing temperatures. We show that such evolution is possible but may only be rapid enough in species with short generation times. Many questions about generalisability of this first study still remain so we continue to study adaptation to warming in different species and contexts,” he concluded.

Darwin’s century-old prediction about flightless insect seems to be on point

Insects are an incredibly varied and diverse group, making up more than half of all known life, with more than a million described species. Many are social, while others are solitary.

Most can fly, while some had this ability but lost it at some point in the past, especially on islands. When Charles Darwin noticed this trend, he speculated that this happens for a very simple reason: so that the insects don’t get blown out into the sea. Those that fly a lot are more likely to get blown, so evolution favors those who don’t.

Many biologists contradicted Darwin’s simplistic assumption. Now, a new study suggests that he might have been right after all — at least partially.

Image credits: Cedric VT.

Flies walk, moths crawl

In between the Antarctic and Australia, a few islands called the Southern Ocean Islands host almost exclusively flightless insects. It’s an extremely peculiar thing, since so many insects fly, and it’s a trend that is also present on many other islands.

“Of course, Charles Darwin knew about this wing loss habit of island insects,” says Ph.D. candidate Rachel Leihy, from the Monash University School of Biological Sciences.

“He and the famous botanist Joseph Hooker had a substantial argument about why this happens. Darwin’s position was deceptively simple. If you fly, you get blown out to sea. Those left on land to produce the next generation are those most reluctant to fly, and eventually, evolution does the rest. Voilà.”

But Hooker, who was an accomplished explorer himself, had different ideas — and Hooker’s own travels to the Antarctic only cemented his ideas. As time passed, biologists seemed to side with Hooker rather than Darwin. Surely there must be some other mechanism at work, most believed. But there seemed to be no clear pattern to explain this. Island size is a poor predictor of flightlessness and climate is also hard to correlate with this.

But few thought to test the idea in the Southern Ocean Islands (SOIs). Leihy and colleagues believe the sub-Antarctic SOIs are an excellent testbed for these hypotheses. They’re pretty cold, food is scarce, and most importantly, they’re some of the windiest places on Earth.

“If Darwin really got it wrong, then wind would not in any way explain why so many insects have lost their ability to fly on these islands,” said Leihy.

They found that out of the indigenous SOI insects, 47% are flightless, compared to 8% for Arctic species, and the 5% global average. In other words, the windier the island, the likelier it is for the insects to ditch flying — essentially making Darwin right.

However, the researchers gave a new spin to Darwin’s idea. Wind is indeed a deterrent to flying, but it’s maybe not because the insects get blown out to sea, but rather because it expends more energy.

Flying is very taxing, it takes a lot of energy to do it. The reason why so many insects can fly is that they’re generally light, which works very well with flying. But if you’re battling a lot of wind, you need to spend more energy than you normally would, which leaves less energy for other things like reproduction. Less reproduction means you’re less likely to spread your genes, and voilà.

Instead, insects on windy islands can choose to redirect the energy for wings and flying muscles to other activities, which seems to be a viable strategy for many species.

It’s remarkable that the ideas of Charles Darwin, the father of evolution, can turn out to be so valuable to this day.

“It’s remarkable that after 160 years, Darwin’s ideas continue to bring insight to ecology,” concludes Leihy, the lead author of the paper.

The study has been published in the Proceedings of the Royal Society B.

This plant evolved camouflage to hide from humans

Fritillaria delavayi is easily recognized thanks to its green leaves and yellow flowers (left). But recently, the plant changed its color to gray, brown-red, and teal in order to camouflage and avoid harvesting by humans.

Most are aware of animal camouflage, where both prey and predator employ various disguises to blend with their environment and avoid attracting attention. However, the same evolutionary pressures that lead some animals to develop camouflage as a defense mechanism are also acting upon other living things, such as plants. Strangely enough, a new study documents how a perennial herb growing in China has evolved camouflage in order to avoid harvesting by human hands.

Plants vs humans

Humans have been deliberately breeding plants since at least the agricultural revolution more than 8,000 years ago. However, we’re far less used to seeing plants evolve in response to human activity without our conscious interference.

For years, Yang Niu, a scientist at the Kunming Institute of Botany at the Chinese Academy of Sciences, has been documenting the fascinating world of plant camouflage. In 2018, he and colleagues in China and the UK published a review concluding that many plants use a host of camouflage techniques long known to be used by animals.

These include blending with the background, “disruptive coloration” (using high-contrast markings to break up the perceived shape of an object), and “masquerade” (looking like an unimportant object predators might ignore, such as a stone).

This makes sense. If plants evolved lush coloring to entice pollinators or enhance photosynthesis, there’s no reason why traits that also offer protection wouldn’t also be favored in some situations.

One prime example is Corydalis hemidicentra, a plant whose leaves match the colour of rocks where it grows. What’s more, different populations of this species look different in different places.

Credit: Yang Niu.

Now, in a new study, Niu and colleagues have documented a new species that employs camouflage — but unlike other plants, this may be the first species to our knowledge that employs camouflage to avoid human predators.

Fritillaria delavayi, a plant that grows in the mountain regions of China, has been harvested by humans for medicinal purposes for at least 2,000 years. They always had green leaves and bell-shaped yellow flowers until recently when many plants colored brown or teal, matching the backdrop of their environment, have been noticed.

Writing in the journal Current Biology, Niu and colleagues say that the plants have evolved camouflage in order to avoid harvesting. It takes around 3,500 flowers to produce a single pound of medicinal product, which can cost up to $218. In rural China, where economic prospects are scarce, the demand for the herb has driven heavy harvesting — and the plants have wised up in response.

“Like other camouflaged plants we have studied, we thought the evolution of camouflage of this fritillary had been driven by herbivores, but we didn’t find such animals,” Niu, co-author of the study, said in a statement. “Then we realized humans could be the reason.”

Using a spectrometer, the researchers recorded how closely the color of the plants matched their environment. Plants from multiple locations were analyzed. The team also kept records of the annual weight of bulbs harvested from 2014 to 2019, which showed where Fritillaria was harvested heavily in each area.

Fritillaria delavayi in an area with low harvesting. Credit: Yang Niu.

Remarkably, the regions with the most intense harvesting also had plants with the most effective camouflage patterns that mimicked their backdrop. Meanwhile, Fritillaria plants that were largely left alone grew green as they have for thousands of years.

“It’s remarkable to see how humans can have such a direct and dramatic impact on the coloration of wild organisms, not just on their survival but on their evolution itself,” said Martin Stevens, an ecologist at the University of Exeter and co-author of the study, in the statement.

“Many plants seem to use camouflage to hide from herbivores that may eat them—but here we see camouflage evolving in response to human collectors. It’s possible that humans have driven evolution of defensive strategies in other plant species, but surprisingly little research has examined this.”

Humans have been selecting crops, animals, and years for so much time that it’s fascinating to hear about unintentional selection for a change. There may be many other examples of this that scientists have yet to learn about.

Fossil Friday: this ancient bottom feeder could have ‘invented’ modern sight

A new paper examines how life first developed advanced eyes and sight, and how this led to an “evolutionary arms race” around 500 million years ago. The findings rely on radiodont fossils, a group of arthropods that were abundant in the ocean at the time.

Artist’s reconstruction of ‘Anomalocaris’ briggsi.

The radiodont order, meaning “radiating teeth”, is comprised of many species with a similar body layout — a head and a pair of segmented limbs that would capture prey. They had circular mouths with sharp, serrated teeth, and were roughly squid-shaped. They likely inhabited the deeper layers of the ocean, at around 1000 meters in depth. Due to the low light levels there, they evolved large, sophisticated eyes in order to catch prey. But this ‘sensor’ upgrade would send ripples throughout life on the planet, the authors explain, making vision a driving force in evolution as it pitted predator against prey.

See food, eat food

“Our study provides critical new information about the evolution of the earliest marine animal ecosystems,” said Professor John Paterson from the University of New England’s Palaeoscience Research Centre, lead author on the study.

“In particular, it supports the idea that vision played a crucial role during the Cambrian Explosion, a pivotal phase in history when most major animal groups first appeared during a rapid burst of evolution over half a billion years ago.”

The development of complex eyes allowed animals to perceive their surroundings better than ever before, which also helped predators spot prey more easily. But sight can also warn the hunted of the hunter, so it became a very powerful driver of evolution — after all, the one with poorer sight might not make it through the day. It has retained its importance up to today when virtually every ecosystem and ecological interaction on the planet is shaped by sight.

Acute zone–type eye of ‘A.’ briggsi. Image credits John R. Paterson, Gregory D. Edgecombe, and Diego C. García-Bellido, (2020), Science Advances.

The fossils used in this study were first unearthed around a century ago at Emu Bay Shale on South Australia’s Kangaroo Island and were comprised of isolated body parts. However, initial attempts to reconstruct the animals based on their fossils were quite unsuccessful and resulted in several “Frankenstein’s monsters”, the authors note. Over the decades, as more radiodont material was discovered, including whole bodies, we’ve gained a better understanding of these animals, their body structure, diversity, even possible lifestyles. Still, the specimens from Emu Bay Shale had some unique properties.

“The Emu Bay Shale is the only place in the world that preserves eyes with lenses of Cambrian radiodonts. The more than thirty specimens of eyes we now have, have shed new light on the ecology, behavior, and evolution of these, the largest animals alive half-a-billion years ago,” says Associate Professor Diego García-Bellido from the University of Adelaide and South Australian Museum, a co-author of the paper.

The team worked with these fossils before. They published two papers describing the fossilized eyes recovered from the site. The first one looked at isolated eye specimens of up to one centimeter in diameter, which remain unassigned to a species up to now. The second paper analyzed the eyestalks of Anomalocaris, a top predator in its day that grew up to one meter in length. The current paper, according to the authors, identifies that first, unknown species: ‘Anomalocaris’ briggsi, a new genus that “is yet to be formally named,” Prof. Paterson said.

Acute zone–type eye of ‘A.’ briggsi. Image credits John R. Paterson, Gregory D. Edgecombe, and Diego C. García-Bellido, (2020), Science Advances.

“We discovered much larger specimens of these eyes of up to four centimetres in diameter that possess a distinctive ‘acute zone’, which is a region of enlarged lenses in the centre of the eye’s surface that enhances light capture and resolution.”

The large lenses of these animals suggest that they could work in the dim light of the deep sea, and were likely very similar to those of modern amphipod crustaceans (a type of prawn-like creature). Anomalocaris briggsi primarily hunted plankton by filtration through its appendages; its eyes helped it spot its meals from the bottom of the ocean.

The body structure of these fossil species also showcases how different feeding strategies dictated differences in sight.

“The predator has the eyes attached to the head on stalks but the filter feeder has them at the surface of the head. The more we learn about these animals the more diverse their body plan and ecology is turning out to be,” says Dr Greg Edgecombe, a researcher at The Natural History Museum, London and co-author of the study.

“The new samples also show how the eyes changed as the animal grew. The lenses formed at the margin of the eyes, growing bigger and increasing in numbers in large specimens — just as in many living arthropods. The way compound eyes grow has been consistent for more than 500 million years.”

The paper “Disparate compound eyes of Cambrian radiodonts reveal their developmental growth mode and diverse visual ecology” has been published in the journal Science Advances.

For all the damage they cause, viruses also help push evolution

“What we learn from our study is that, in general, viruses have major roles in driving evolution,” one researcher explained. “In the long-term, viruses have positive impacts to our genome and shape evolution.”

While the general principles of evolution are fairly straightforward, the details behind the process is immensely complex. What if someone told you, for instance, that viruses help fine-tune evolution; that these dreaded organisms that aren’t really organisms can help push the survival of a species? As weird as it sounds, that’s one takeaway from the two studies published by the Cincinnati Children’s Perinatal Institute and at Azabu University in Japan.

The scientists looked at lab mice and human sex cells, or to be more precise, at the germline cells — the cells that form the egg, sperm, and the fertilized egg that pass on their genetic material to the progeny (offspring).

Specifically, they looked at the set of all RNA of these sex cells, something called transcriptomes.

These transcriptomes contained either the male or the female half of chromosomes passed on as genetic materials when species mate. In other words, they define the unique character of sperm and egg as they pass on genetic information to the next generations.

The two published papers look at some of the processes behind these transcriptomes. Satoshi Namekawa, principal investigator on both papers, combined biological testing of mouse models and human germline cells with computational biology to see how genes are produced and reorganized following sexual reproduction. He found that a key element in this process is something called super-enhancers.

“One paper, Maezawa and Sakashita et al., explores super-enhancers, which are robust and evolutionally conserved gene regulatory elements in the genome. They fuel a tightly regulated burst of essential germline genes as sperm start to form,” Namekawa said.

Super-enhancers are regulated by two molecules that act as gene control switches. This is where the second study comes in, Namekawa explains.

“The second study, Sakashita et al., involves endogenous retroviruses that act as another type of enhancer – gene regulatory elements in the genome – to drive expression of newly evolved genes. This helps fine tune species-specific transcriptomes in mammals like humans, mice, and so on.

Endogenous retroviruses are normal components of the human genome and account for around 8% of our DNA — in fact, they account for over 5% of many mammals’ DNA. Also referred to as “jumping genes”, these retroviruses have traditionally been considered threats because they can disrupt some genes. However, over the past few decades, researchers have found that these viruses can actually act as regulatory elements for our genome.

This is exactly what Namekawa and colleagues have found. Endogenous retroviruses can help fine-tune transcriptomes, essentially helping a species’ evolution and diversity.

Super-enhancer switching drives a burst in gene expression at the mitosis-to-meiosis transition, Nature Structural & Molecular BiologyDOI: 10.1038/s41594-020-0488-3 

Yum or yuck? Scientists find how mosquitoes evolved a taste for human blood

Not a lot of people know this, but out of the 3,500 mosquitoes species out there, just a few bite humans. This immediately begs the question: what’s so special about these species and their relationship with humans?

In a new study, researchers investigated the evolutionary pathways that enabled some mosquitoes to adapt to human settlements and grow a taste for our blood.

The yellowfever mosquito Aedes aegypti. Credit: Wikimedia Commons.

According to the new study, increased population density played a major role in mosquito adaptation to human blood. However, a dry climate was even more important.

That’s quite an important insight to have, considering mosquitoes — small and annoying as they may be — are known to spread dangerous infectious diseases. For instance, the findings suggest that increased urbanization in the coming years might increase mosquito biting and the risk of disease in tropical regions and beyond.

“We found that different African populations of the mosquitoes that spread dengue, Zika, chikungunya, and yellow fever vary widely in how attracted they are to humans. Mosquitoes living near dense cities were more willing to bite humans than mosquitoes in rural areas, but climate was even more important: in places with intense dry seasons mosquitoes showed a strong preference for humans,” Noah Rose, a researcher at Princeton University and co-author of the new study, told ZME Science.

“Mosquitoes that prefer humans showed differences in the same sets of genes, so we think this preference evolved just once about 5,000-10,000 years ago, likely as an adaptation helping them survive long dry seasons. Many cities in Africa are growing extremely quickly; our model suggests that mosquitoes in these places may evolve greater preference for human hosts, which could lead to them spreading disease more effectively.”

The Princeton researchers focused on their attention on Aedes aegypti, a highly successful mosquito species that inhabit areas in tropical, subtropical, and in some temperate climates, and the primary vector of infection for dengue, Zika, yellow fever, and Chikungunya virus.

In the grand scheme of things, Aedes aegypti is an oddity because it is one of only a handful of species from Africa that bite humans. The researchers used this to their advantage since it allowed them to empirically verify where specifically mosquitoes interact with humans the most and where they prefer to bite other animals instead.

“This study was very challenging to conduct, because we had to collect mosquitoes from a really wide range of habitats across a huge geographic range. So we were collecting mosquitoes everywhere from in the middle of a rainforest to the middle of a huge bustling city. Each of these places has unique challenges, whether it’s watching out for dangerous wild animals like lions and elephants, or getting out of a giant traffic jam on a busy city street. This was only possible because of the experience and expertise of our whole scientific team, which included people with years of experience in each of the countries and habitats in which we collected mosquitoes,” Rose said.

Using special traps, the team collected Ae. aegypti from outdoor sites in more than 27 locations across sub-Saharan Africa. In the lab, mosquitoes from each population were exposed to various animal scents (such as guinea pigs, quail, and humans) in a controlled environment in order to assess their preferences. The analysis of the recorded data suggests that mosquitoes from dense urban cities were attracted to people more than those from rural or wild areas.

But since this pattern of preference for human odors only held in extremely dense modern cities, it is highly unlikely that this was the original reason why Ae. aegypti mosquitoes evolved to bite humans.

The secondly identified pattern of mosquito preference for human blood seems more revealing and points to a more plausible avenue for genetic adaptation. Specifically, the researchers found that the insects that lived in drier, hotter regions had a strong preference for human scent when compared to other animal scents.

Somewhat counter-intuitively, the climate seems to have mattered more than having many blood bags on two legs in close quarters. Even more surprisingly, many mosquitoes living in dense cities don’t particularly prefer to bite human hosts — it is only when cities become extremely dense and are located in areas with intense dry seasons that our blood becomes very enticing to the insects.

“I think it’s because mosquitoes in habitats with intense dry seasons become particularly dependent on humans for their life cycle. Aedes aegypti larvae live in small, contained bodies of water. In the ancestral state, this was places like tree-holes or sometimes rock pools. Later, they adapted to surviving in human-associated containers like pots of stored water, or more recently buckets and tires,” Rose wrote in an email.

“In places with long, hot dry seasons, there are very few natural habitats for mosquitoes, but they may be able to survive year round by taking advantage of the habitat that humans make for them by keeping water stored near their homes. So these mosquitoes have a very close relationship with humans, which may have led them to specialize on biting humans.”

Genes concentrated in a few key regions of the mosquito genome seems to have driven this evolutionary shift in the insects’ biting preferences.

The researchers also modeled how climate change and expected urban growth might shape mosquito preferences in the near future — and it doesn’t look too good.

While climate change isn’t expected to cause important changes in dry season dynamics in sub-Saharan Africa over the next 30 years, many cities are expected to expand massively.

“Surprisingly, when we checked what our model predicts for near-term climate change in the next few decades, we didn’t see major changes in the precipitation variables that are important for mosquitoes. However, cities are growing extremely quickly, so we saw that our model predicts more human-biting in many cities across Africa due to urbanization effects. Longer term climate change could drive important behavioral shifts, but we haven’t extended our model that far — in the near term the urbanization effects seem to be more important,” Rose said.

In the future, Rose and colleagues will further investigate the interplay between climate, genetics, and urbanization in mosquitoes’ biting preferences.

“Overall, we hope this study will help people understand that all mosquitoes are not the same. Some spread disease much better than others. Even within species, there is enormous diversity. Mosquito history and human history are intertwined, and global changes driven by humans are also likely to drive further mosquito evolution,” Rose concluded.

The findings appeared in the journal Current Biology.

Art history is uncovering hidden patterns of fruit and vegetable evolution

(A) Facsimile of wall painting from the tomb of Sennedjem at Deir el-Medina (original ca. 1293–1213
BCE). (B) The Harvesters by Pieter Bruegel the Elder, 1565.

For years, biologists have been tapping into the genomes of both modern and ancient crops in order to trace their long and rich history — from wild plains to your dinner table. However, there are still significant gaps in the timeline of both fruit and vegetable evolution, despite the availability of sophisticated genetic sequencing technology.

An unlikely pair of researchers are now seeking to address these gaps using a unique approach. In a new study, Ive De Smet, a plant biologist at the VIB-UGent Center for Plant Systems Biology in Belgium, and David Vergauwen, an art history lecturer at Amarant in Belgium, demonstrate how old paintings can be highly useful in tracking how fruit and veggies evolved across the last centuries.

Are you intrigued? If so, you’re not alone. In fact, you’re encouraged to lend a hand as the two researchers are looking to the public to extend a helping hand by providing pictures of paintings that depict plant-based food.

Evolution hidden in art

 Ive De Smet (left) and David Vergauwen in a field of wheat, one species that has been the focus of their research. Credit: Liesbeth Everaert.

If you were to travel back in time ten thousand years, you would have been in for a big surprise. Virtually, all the succulent fruits and savory vegetables we all dearly love looked nothing like they do today. In fact, it took countless generations of selective breeding to turn measly wild plants into highly productive food crops. For instance, modern corn is 1,000 times larger and contains at least four times more sugar than the wild variety that used to grow on the plains of Mexico ten thousand years ago.

Sometimes these transitions are obvious, but other times the jigsaw puzzle is more challenging to piece together, which is why biologists are grateful for any input they can find — so why should art be an exception?

For De Smet and Vergauwen, who have been friends for 30 years since high school, this uncanny union is not at all as esoteric as it may sound. Their foray into the intersection between art and evolutionary biology first began during an unsuspecting trip to the Hermitage Museum in Saint-Petersburg.

“A couple of years back, we were in Saint-Petersburg (Russia). At the Hermitage we started a discussion about the fruits depicted by Frans Snyders. The question was: did this particular piece of fruit look like this in the 17th century or was Snyders a bad painter? It was well worth the discussion, since the next day, on the train to Tsarkoe Selo, we started to wonder if there were other fruits or vegetables that had similar stories behind them. Years later, we are still investigating. It turned out to be a valuable (and hardly used) approach to combine our expertise on the level of (art) history and genetics. Maybe there are not that many art historians who have biologists as their best friend and the other way around?” De Smet told ZME Science in an email.

Intrigued by the ideas they were discussing back and forth, the two researchers scoured the available literature for any work that combines art history and genetics. They hit a blank wall.

“So, we started to do some digging and I guess we’ve never stopped digging. Some friends play tennis together or go fishing. Ive and David visit museums, meet other scholars, look at paintings and study the history of our modern foods,” De Smet recounted.

Content that they found a niche, the two researchers set to work right away looking for clues that might inform them what fruits and vegetables looked like in the past.

For example, their investigations of ancient Egyptian depictions of watermelons showed that the fruit had the familiar light and dark green stripes even during those times.

In conjunction with the DNA sequencing of a watermelon leaf retrieved from an Egyptian tomb, this suggests that the fruit was domesticated as early as 4,000 years ago. But despite its similar appearance to modern varieties, this ancestral strain was similar in taste to cucumbers, predating sweet melons by thousands of years, according to a 2019 paper authored by De Smet and Vergauwen.

Be on the lookout for paintings depicting plants

Although old artwork can provide valuable clues as to how plants used to look centuries ago, or even before their domestication, such assessments aren’t at all straightforward.

Painters often depict the world with an artistic license, which makes their artwork unreliable as an accurate reflection of the world. Even some modern painters can’t be trusted. For instance, if you trust Picasso to depict a watermelon as it really looks, you’ll surely be in for a surprise. This is why expertise in art history is essential.

“How do we know a painting is reliable? If you look at a cubist work by Picasso to figure out what a pear looked like in the early 20th century, you will be disappointed. That is where art history comes in. Some paintings are reliable in only some aspects, some are totally reliable and others not at all, like the Picasso. The works by Jeroen Bosch might show a morphologically correct depiction of a strawberry, but it might be taller than the people next to it. It would be fanciful to suppose that there were indeed any such large strawberries, but if the strawberry is morphologically correct, we might draw conclusions from that,” De Smet told ZME Science.

“So how do we know what to believe? That is a matter of trusting the evidence. If a painter depicts clothes correctly and we can verify that with specimens from a museum or other paintings, if a painter depicts musical instruments (violins or harpsichords) that are still in a museum and they match up, if a painter depicts architecture that is still around (say the central market place of Antwerp) and it checks out, then we do not have a reason to suppose that we would go about his work in a totally different way when it comes to perishables like fruits and vegetables. It is a simple question of checking the reliability of your source and trusting the evidence. And often it is also a matter of numbers. If something is depicted only once it might be an oddity (or a poor-quality painter), but if something pops up regularly it might indeed be how it (at least in part) looked like.”

This is why De Smet and Vergauwen hope to inspire people to participate in a citizen science project by supplying pictures of paintings depicting fruits and vegetables.

“We can only travel so much, so this is one of the reasons why we started this Crowd Sourcing campaign, the tap into resources we would normally not be able to,” said De Smet.

“We cannot be everywhere. Sure, we have visited the Hermitage, the Louvre, the National Gallery in London, etc., but if an interesting 17th-century tomato is depicted in the kitchen of a Spanish monastery that is almost never open to visitors, we run the risk of never finding out about that. That is why we need help. We want to find as much material as possible. Catalogues are of no help, because a mythological painting with Perseus freeing Andromeda can have a perfectly fine orange in the background, but the description, the title or a small picture of that painting will never give us a clue of where to find it. We need people to notice it. Then we need them to report their findings. We came up with this citizen science idea quite early on in our project and we are looking at ways to finance an app to help people to help us. There is still so much to do.”

That’s not to say that old paintings can reveal instances of plant evolution that genomic analyses have missed, although this isn’t beyond the realm of plausibility.  Instead, art history and genetics can join hands to construct more accurate timelines of when a particular fruit or vegetable crop enters common usage.

Take carrots, for instance. Today, the popular vegetable is ubiquitously recognized due to its orange appearance thanks to high carotenoid contents. However, 17th-century paintings from the Dutch Golden Century depict carrots in white, red, yellow, and orange. This isn’t some creative fluke — that’s really how carrots used to look when the painters were alive.

(A) Pieter Aertsen, The Vegetable Seller (1567). The drawing with color overlay indicates the positions of orange or purple carrots on the painting and a likely black radish or
parsnip (grey). (B,C) illustrate some of the major components leading to carrot colour. The diagrams highlight the enzymes and/or major products in carotenoid (B) and anthocyanin pathways (C). Credit: Trends in Plant Science, Vergauwen and De Smet.

What’s intriguing is that this approach can be extended for virtually all instances of evolution that may have been captured by art, from plants to animals. But, for now, the two researchers are content to stick to what they know best: art history, genetics, and a passion for visiting museums.

“I guess we will never stop visiting museums. This was a hobby of ours long before we started this project. The only difference is that now we can tell our wives that we have to take a trip “for work’,” the researchers said.

So you’re an art aficionado but also a science nerd? Then drop a line to the researchers at artgeneticsdavidive@gmail.com — your help and keen eye will be surely appreciated. 

Theory by Darwin is proven 150 years after his death

The theory of evolution through natural selection by biologist, geologist, and naturalist Charles Darwin made him one of the most influential people in history. But, in reality, this is not his only contribution to science.

Credit Wikipedia Commons

His investigations supported the concept that humans were animals and members of a single species. He also looked at sexual selection and its influence on beauty, the pollination of orchids, and the evolution of human psychology.

Although he died in 1882, his research still shapes our understanding of the world to this day — and are still relevant scientific topics. A new study by researchers from the University of Cambridge confirmed one of the hypotheses proposed in Darwin’s origins of species.

After analyzing a multitude of studies on small mammals, the researchers have shown that the most diverse lineages have both more species but also subspecies, which confirms that they have a very important role in evolution.

“Darwin said that animal lineages with more species also have to have more varieties, in other words, subspecies,” said in a statement Laura van Holstein, one of the researchers. And that is exactly what has been confirmed, thanks to the analysis of the studies carried out with small mammals.

A species is a group of animals that can reproduce freely amongst themselves. Some species can contain subspecies — populations within a species that differ from each other by having different physical traits and their own breeding ranges. The study confirmed with new experimental data that evolution doesn’t occur in the same way and in the same speed in all mammals since not all of them face the same type of geographical barriers.

“We found the evolutionary relationship between mammalian species and subspecies differs depending on their habitat. Subspecies form, diversify and increase in number in a different way in non-terrestrial and terrestrial habitats, and this, in turn, affects how subspecies may eventually become species,” van Holstein said.

For example, van Holstein said, if a natural barrier like a mountain range gets in the way, it can separate animal groups and lead to different evolutionary journeys. Flying and marine mammals have fewer physical barriers in their environment.

There’s a strong relationship between the diversity of species and the diversity of subspecies, which indicates that the second is very important for the appearance of the first, the researchers argued. In fact, this relationship confirms that subspecies can be considered an early stage of speciation – the formation of new species.

The research represents a warning over the impact humans can have on animal habitats, both today and on their future evolution. The findings can help create new conservation strategies for endangered species across the world.

“Evolutionary models could now use these findings to anticipate how a human activity like logging and deforestation will affect evolution in the future by disrupting the habitat of species,” van Holstein said. “Animal subspecies tend to be ignored, but they play a pivotal role in longer-term future evolution dynamics.”

The study was published in the journal Proceedings of the Royal Society B.

African hunter-gatherers prefer squatting to sitting — and this may explain why they’re healthier

Credit: David Raichlen.

Humans conquered this world thanks to our restless sense of adventure and ingenuity. At the same time, people are also some of the foremost slackers in the animal kingdom. This can be problematic if you live a modern lifestyle that’s predicated on sedentary activities, which is why it’s interesting and perhaps even useful to understand how our ancestors rested when they took a break.

According to researchers at the University of Southern California, evolutionary pressures favor the conservation of energy. But if that’s the case, why do we sit in the first place? I mean, studies suggest that sitting for prolonged periods of time hurts your heart, shortens lifespan, increases the risk of diabetes, ruins your back, and can even lead to varicose.

These problems are almost nonexistent for Tanzanian hunter-gatherers known as the Hadza, one of the few people left in the world that continue to live the way humans have lived thousands of years ago.

Researchers led by David Raichlen, a professor of human and evolutionary biology at the University of Southern California, strapped tracking devices to Hazda participants in order to measure their sedentary behavior and muscle activity. This was a lot more challenging to do than it sounds since the researchers had to work in the field with the Hazda, in a remote part of Tanzania without access to electricity, food, or running water.

Although the Hazda were very active throughout their day, engaging in high-intensity physical activity that was up to three times the 22 minutes per day recommended by US federal health guidelines, they also had very high levels of inactivity.

Hazda participants in resting postures Photo: David Raichlen.

In fact, the Hazda spend as much time being sedentary as humans in developed countries — around 9 to 10 hours a day. But, despite this, the incidence of diseases associated with long periods of sitting in industrial countries is almost nonexistent.

“The biggest surprise was finding that the amount of time spent in sedentary behaviors was similar in the Hadza and in US populations. We expected hunter-gatherers to rest less,” Raichlen told ZME Science.

However, when the hunter-gatherers are resting, they’re not sitting. Instead, their favorite resting positions are kneeling and squatting.

Special devices that measured muscle contractions in the lower limbs showed that squatting and kneeling involved more muscle activity compared to sitting. This means that the Hazda are stressing their muscles even when resting, contributing to more physical activity throughout the day.

In contrast, the only time people work their legs while sitting in their office jobs is when they bend their knees.

“We suggest these more active resting postures are likely ancient and may help explain why the recent development of chair-sitting is harmful,” Raichlen said.

While behaviors that lead to conservation of energy were favorable for our ancestors, this isn’t necessarily true anymore for individuals who live in industrialized countries.

Does that mean that you should swap your standing desk for a squat rack? That’s just impractical — but there is value in being aware that prolonged sitting hurts your health.

“Given that most of us stopped squatting and kneeling after childhood, we don’t recommend using those postures necessarily. However, breaking up periods of sitting, or finding ways to increase muscle activity when sedentary may be a good idea,” Raichlen told ZME Science.

“We are continuing to examine physical activity and inactivity from an evolutionary perspective and are planning experiments to detail the physiological effects of different resting postures. We believe that this study is a good example of how an evolutionary perspective can enhance our understanding of how behaviors influence health,” he added.

The findings appeared in the journal Proceedings of the National Academy of Sciences.

How ancient gut microbes might have shaped human evolution

Humans are, in fact, mostly microbes. There are over 100 trillion microbes living inside the human body, which outnumber our human cells ten to one. Most of these microbes live inside the gut, particularly in the large intestine, and are collectively known as the ‘microbiome’. According to a new study, the microbiome may have played a critical role in our ancestors’ quest to spread across the world, allowing them to survive in new geographical areas.

“In this paper, we begin to consider what the microbiomes of our ancestors might have been like and how they might have changed,” Rob Dunn of the North Carolina State University and lead author of the new study said in a statement. “Such changes aren’t always bad and yet medicine, diet, and much else makes more sense in light of a better understanding of the microbes that were part of the daily lives of our ancestors.”

Dunn and colleagues analyzed data gathered by other studies, comparing the microbiota among humans, apes, and other non-human primates.

The bacteria in the microbiome help digest our food, regulate our immune system, protect against other bacteria that cause disease, and produce vitamins including B vitamins B12, thiamine and riboflavin, and Vitamin K, which is needed for blood coagulation. It was only in the late-1990s that the existence of the microbiome was generally recognized.

The new study’s results suggest an extraordinary variation in the composition and function of human gut microbes depending on a person’s lifestyle and geographical location. It would mean that our gut microbes have had to adapt to new environmental conditions and likely did so quickly.

When our ancestors migrated to a new region, they not only encountered novel climates and habitats, but also new kinds of foods and diseases.

By having an adaptive microbiome, these ancestors could digest novel foods that they encountered in a local region while also increasing their resilience against new diseases.

As such, the authors concluded in the journal Frontiers in Ecology and Evolution that microbial adaptation might have been critical to facilitating the spread of humans in a range of environments.

Such microbial adaptations were easily transmitted from human to human thanks to the tight-knit social structure. Yet, our ancestors not only shared microbes among themselves, but they also outsourced them into food through fermentation.

By fermenting food, human ancestors virtually extended their guts outside of their bodies as microbes allowed digestion to begin externally.

Fermentation allowed humans to store food for long periods of time and stay in one place, facilitating larger communities. Fermented foodstuff also re-inoculated the consumers, ensuring that in time their microbiota became more similar to each other compared to individuals living in other groups. So, in many ways, the story of human evolution is very much intertwined with that of microbes.

“We outsourced our body microbes into our foods. That could well be the most important tool we ever invented. But it is a hard tool to see in the past and so we don’t talk about it much,” says Dunn. “Stone artifacts preserve but fish or beer fermented in a hole in the ground doesn’t”.

The authors caution that their hypothesis needs to be validated by further studies, preferably performed by an interdisciplinary team made of paleoanthropologists, medical researchers, ecologists and more.

“We are hoping the findings will change some questions and that other researchers will study the consequences of changes in the human microbiome,” says Dunn. “Hopefully the next decade will see more focus on microbes in our past and less on sharp rocks.”

Our ancestors may have always walked on two legs, 10-million-year-old ape suggests

Upright walking is one of the hallmarks of our species yet the origin of human bipedal locomotion is still a subject of heated debate among experts and scholars. How did our ancestors ever make the jump from walking on all fours to an upright gait? Well, what if our early ancestors were far more equipped to walk on two legs than we’ve given them credit for? This exciting possibility was recently proposed by researchers who studied the fossils of a 10-million-year-old small-sized ape.

Rudapithecus has a more flexible lower back than modern African apes, which probably allowed it to stand upright more like humans. Credit: John Siddick.

Carol Ward, an anthropologist at the University of Missouri, analyzed the pelvis bone belonging to a Rudapithecus specimen. The fossil was unearthed near Rudabánya, an old mining town in Hungary.

The pelvis was initially discovered by David Begun, a professor of anthropology at the University of Toronto. Previously, Begun had studied limb bones, jaws, and teeth belonging to Rudapithecus, showing that it was a relative of modern African apes and humans.

The new study now offers information about Rudapithecus‘ locomotion and posture.

“Rudapithecus was pretty ape-like and probably moved among branches like apes do now—holding its body upright and climbing with its arms,” said Ward, a Curators Distinguished Professor of Pathology and Anatomical Sciences in the MU School of Medicine and lead author on the study. “However, it would have differed from modern great apes by having a more flexible lower back, which would mean when Rudapithecus came down to the ground, it might have had the ability to stand upright more like humans do. This evidence supports the idea that rather than asking why human ancestors stood up from all fours, perhaps we should be asking why our ancestors never dropped down on all fours in the first place.”

The pelvis was not complete but using modern 3-D modeling techniques, the researchers filled in the blanks and digitally completed the bone. The reconstruction allowed them to then compare Rudapithecus’ pelvis to modern animals.

Modern African apes, such as chimpanzees and gorillas, have a long pelvis and short lower back. For this reason, they typically walk on all fours when they’re on the ground. Humans, on the other hand, have much more flexible lower backs, which allows them to walk on two legs without expending a lot of energy.

If humans evolved from an ancestor built like an African ape, significant changes would have had to be made to the pelvis and lower back. This is why Ward believes that it is plausible that we evolved from an ancestor that looked more like Rudapithecus — the transition to upward locomotion would have been more straightforward.

A Rudapithecus pelvis fossil, center, overlain on a skeleton of a siamang, compared with a macaque on the left and orangutan on the right. Credit: University of Missouri

“We were able to determine that Rudapithecus would have had a more flexible torso than today’s African apes because it was much smaller—only about the size of a medium dog,” Ward said. “This is significant because our finding supports the idea suggested by other evidence that human ancestors might not have been built quite like modern African apes.”

In the future, the researchers plan on conducting more 3-D models of the other Rudapithecus fossils in order to learn more about how it moved about, perhaps offering more insights into how our ancestors left the safety of canopies to bravely explore the world on two legs.

The findings were reported in the Journal of Human Evolution.

Snakes had hind legs for 70 million years

Snakes have been around for at least 170 million years, since the upper Middle Jurassic Period, but scientists know surprisingly little about their evolution due to a sparse fossil record. What’s certain is that they once had hind legs and only later became limbless. A new study suggests that this transition took place over a much larger period of time than previously thought.

Render of Najash by Raúl O. Gómez, Universidad de Buenos Aires, Buenos Aires, Argentina.

An international team of researchers recently described an ancient snake with hind limbs, known as Najash rionegrina (in the bible, Nahash is a legged snake, which is Hebrew for snake).

The first description of Najash, which was first discovered 13 years ago, was based on a fragmented skull. This led to a lot of guesswork concerning the primitive snake’s appearance. What was clear even from this incomplete specimen is that Najash had robust hindlimbs and unlike other such ancient snakes, it crawled through the desert rather than swam through the ocean. In this sense, Najash is unique because of its terrestrial habitat.

In their new study, researchers led by Fernando Garberoglio from the University of Buenos Aires analyzed eight skulls, one of which was almost perfectly intact, found in northern Patagonia in Argentina. What makes the fossils particularly important is the fact that they’ve been preserved in three-dimensions, uncrushed, whereas most fossils are flattened like a pancake. As such, these fossils allowed the researchers to answer some longstanding questions about how snakes evolved their highly specialized skulls.

Fossilized skull of Najash found in Argentina. Credit: Fernando Garberoglio.

Micro-computer tomography scans revealed that Najash had a combination of lizard and modern snake features. It had a lizard-like cheekbone but lacked a bony arch connecting the skull the cheekbone. It also had intermediate features between snakes and lizards, such as a jaw point. According to the researchers, though, Najash had many of the flexible joints present in the skull of modern snakes.

“Snakes are famously legless, but then so are many lizards,” said Dr. Alessandro Palci, co-author of the study and a researcher at Flinders University.

“What truly sets snakes apart is their highly mobile skull, which allows them to swallow large prey items.”

“For a long time we have been lacking detailed information about the transition from the relatively rigid skull of a lizard to the super flexible skull of snakes.”

The 95-million-year-old fossils discovered in the La Buitrera Paleontological Area in Argentina also fill in the blanks in Najash‘s evolutionary tree.

Previously, scientists used to think that snakes trace their origins in blind, burrowing lizards. Scolecophidians, a group of living small, worm-like burrowing snakes, share common features and are considered the most primitive snakes alive today. But the newly described fossils show that skulls in the lineage of ancient snakes had nothing in common with scolecophidian snakes.

The newly constructed snake family tree remarkably shows that the slithering creatures had small hind legs for the first 70 million years of their evolution before limbless, modern snakes appeared.

“These primitive snakes with little legs weren’t just a transient evolutionary stage on the way to something better,” said Professor Mike Lee, a researcher at Flinders University and South Australian Museum.

“Rather, they had a highly successful body plan that persisted across many millions of years, and diversified into a range of terrestrial, burrowing and aquatic niches.”

The findings appeared in the journal Science Advances.

Investing in flashy display pays off for species that mate for life

Zebra finches. Credit: Flickr, NeilsPhotography.

Darwin’s theory of natural selection predicts that it is more advantageous for males to seek out as many mates as possible. Some species, however, mate for life and often the males continue to dazzle females with courting rituals even after the pair has bonded and the female starts ovulating. Such mating behaviors have been more challenging to explain from an evolutionary standpoint.

Biologists at the University of Chicago and the University of North Carolina have developed an evolutionary model that explains why many birds continue to make elaborate displays of plumage and dances after they mate with a female. This all makes sense, the model suggests, because the male’s investment also elicits more investments on the female’s side, which devotes more energy into the brood. But, this form of sexual cooperation, it turns out, involves a delicate balance of inputs and outputs.

“Many bird researchers can tell a story like the experience I once had in the UK. I caught a female goldfinch, placed her in a bird bag and carried it back to the banding station. All the way back to the station, her mate followed, calling,” said UChicago biologist Trevor Price, who is the senior author of the new study.

“He waited impatiently in a nearby tree as I banded the female, and when I released her the pair flew off together in close company, twittering. This kind of thing happens in many other species, too, so forming a strong pair bond and emotional attachments between a male and female is evidently not only a feature of humans.”

In the 1980s, ornithologist Nancy Burley showed that slipping red bands onto the legs of male zebra finches (Taeniopygia guttata) turned them into sex magnets. The male finches, which already have red beaks, may elicit greater excitement in females by being even more flashy with the red bands. Burley famously showed that the female zebra finches respond to this mating display by working harder for the brood, raising more young.

However, while this strategy works very well for males, which now get to have more offspring that pass on their genes, females seem to be at a disadvantage because they have to invest more energy, lowering her chances of raising more healthy offspring in the future.

In their new study, Price and colleagues developed a mathematical population genetic model that evaluated various mating scenarios. The model weighed the cost of investment with the number of hatchlings that a pair could raise over many generations.

As an example, a female bird might lay three eggs, but a male with more blue coloration would cause the female to lay four eggs. Because blue males will have more offspring than duller males, blue males will become increasingly common over generations.

At the same time, caring for four eggs instead of three comes at a great cost to the female. Those females who only have to care for three eggs are at an advantage, so they become more common among the population. Running this game will ultimately result in all males being blue and all females laying three eggs. What happens, however, is that males that do not invest in display will prompt females to lay only two eggs, which is not good for either.

The evolutionary model produced by the researchers shows that the most mutually beneficial strategy is for males to stick around and display their key reproductive traits. This turned out to be true for any color or kind of display. What’s more, the female can become so dependent on a male’s display that she may stop ovulating in the absence of the male, as previously shown in ring doves.

“The models enable us to see the wide ranges of conditions that can cause displays to become stuck in the population, evolutionarily, and that can lead to this result,” said Maria Servedio, a researcher at the University of North Carolina and co-author of the study published in the Proceedings of the National Academy of Sciences.