Tag Archives: tail

This mutation may explain how humans lost their tails

Credit: Pixabay.

Tails are almost a standard accessory in the animal kingdom, and for good reason too. Fish rely on their tails for propulsion, cows use them as fly swatters, crocodiles store fat in them, and monkeys rely on tails for balance and even to grip things with them. Humans actually have a tail too as embryos, however, it regresses into fused vertebrae becoming the coccyx, also known as the “tailbone”.

This tailbone is actually proper evidence that somewhere in our evolutionary journey something happened that made us lose our tails. We’re not alone either. Humans belong to a group called great apes, and along with gorillas, orangutans, chimps, and bonobos, none of us have tails. The lesser apes like gibbons don’t have tails either. What gives?

If you’re sorely missing your tail, you may have a pesky mutation to blame, according to a new study that appeared this week in the preprint server bioRxiv.

Where’s my tail?

The oldest known primate fossils are around 66 million years old, around the same time the dinosaurs went extinct. These ancestors had full-fledged tails that were likely handy when living in canopies. The utility of this flexible body part can be attested to by the fact that even after all these years, most living primates and the vast majority of monkeys still sport a tail.

On the other hand, by the time Proconsul, the most primitive ape that is well-known from a fossil skeleton, appeared some 20 million years ago, it had no tail at all.

Why exactly humans and their closest relatives lost their tails has been a matter of debate for some time. What biologists have noticed is that apes can walk with upright stances thanks to a shorter lumbar region enabled by the absence of the tail. Meanwhile, new world monkeys use all fours.

As such, the loss of the tail can be seen as an adaptation to a particular environment, which allowed our ape ancestors to leave trees and walk on the ground. With some adjustments, early humans could not only walk but jog over the grassland.

Bo Xia, a graduate student in stem cell biology at N.Y.U. Grossman School of Medicine, has always been curious why humans lack tails. Being a scientist, he decided to answer this question himself, or at least attempt to, by zooming in at the molecular level.

Xia and colleagues started his journey by studying how tails form in animals that sport them. He found that early in the embryo’s development, some genes switch on that instruct stem cells to develop into vital skeletal structures, such as the neck, lumbar region, and eventually a chain of vertebrae and muscles that form the tail.

According to the researchers, we know of about 30 genes that are fundamental to tail development in various species. When they compared the DNA of six species of tailless apes to nine species of tailed monkeys, the scientists found a mutation shared by apes and humans but missing in monkeys.

The mutation affects a gene called TBXT, which is interestingly enough one of the first genes ever discovered more than a century ago. The mutation found by Xia is found in the middle of the TBXT gene and is virtually identical in humans and other apes.

Back in the lab, the researchers genetically engineered mice that had the TBXT mutation. Lo and behold, many embryos lacked a tail while others grew a very short, stumpy one.

“We propose that selection for the loss of the tail along the hominoid lineage was associated with an adaptive cost of potential neural tube defects and that this ancient evolutionary trade-off may thus continue to affect human health today,” the researchers wrote.

About 20 million years ago, an ancient ape was born with this mutation and reproduced significantly more thanks to it — rather than in spite of it — passing it on to offspring. Eventually, the TBXT mutation became a defining feature of the ape genome — and it’s likely not alone.

The genetically engineered mouse embryos developed a range of altered short tails. The human tailbone, however, basically looks identical across individuals, suggesting other mutations may be involved in its development.

So if you ever wondered “Dude, where’s my tail?” you can now point your finger at TBXT.

Crumbled comet helps researchers understand how their tails form

Last year, researchers spotted what was going to be the brightest comet seen since 1997: C/2019 Y4 ATLAS. It is now helping us understand how comets form their tails.

The comet’s break up in April 2020, captured by Hubble. Image credits NASA / ESA / STScI / D. Jewitt (UCLA).

Much to their dismay, however, this body broke down into fragments sometime in April 2020, robbing everybody of a shining view. Not all is lost, however, as NASA and the European Space Agency’s Solar Orbiter managed to do a flyby of the fragments, giving us a very rare look at what happens after a comet breaks up.

The tail end

ATLAS was supposed to become easily visible even with the naked eye as it passed Earth in May of last year. But one month before that could happen, our satellites showed, ATLAS got progressively brighter. Finally, it crumbled before reaching Earth. The Hubble Space Telescope captured this event, despite it happening over 90 million miles away from our planet. Each fragment is around the size of an average house.

Still, the comet’s tail persisted after the breakdown, so the Solar Orbiter was tasked to observe the remains. All of the craft’s instruments were used to probe ATLAS’s remains for information, including an energetic particle detector, magnetometer, a radio wave detector, and solar wind analyzer.

Data from the magnetometer was particularly interesting, as it allowed ground control to see how the magnetic field of the comet’s tail interacted with the magnetic field carried through the solar system by the solar wind. This interaction is known to produce ion tails around comets, a fainter and smaller counterpart to their visible dust tails.

Based on the data recorded here, the team was able to model the magnetic field generated by the initial comet, revealing a surprising fact: it is weakest around the central dust tail. This is most likely produced by the comet’s ‘wake’ as it barrels through incoming solar winds. The comet’s ion tail is produced by this magnetic field warping in combination with chemical ions produced by the melting of the comet’s core.

“This is quite a unique event, and an exciting opportunity for us to study the makeup and structure of comet tails in unprecedented detail,” said Lorenzo Matteini, a solar physicist at Imperial College London and leader of the recent work, in a Royal Astronomical Society press release. “Hopefully with the Parker Solar Probe and Solar Orbiter now orbiting the Sun closer than ever before, these events may become much more common in future!”

The event, although it might seem inconsequential in the grand scheme of things, lets us understand comets and outer space just a little bit better. While we don’t have a practical use for such data right now, they might come in handy when and if humanity takes to the stars in meaningful numbers.

The findings have been presented at the National Astronomy Meeting 2021.

Alligators can regrow their tails, and it could help us heal our own wounds better

Young alligators sometimes lose their tails, but they can grow them back to a certain extent, a new study reports. Each animal can regrow around three-quarters of a foot of tail, roughly equivalent to one fifth of their total body length.

Image via Pixabay.

The team used advanced imaging techniques to determine whether alligators have the same type of regenerative tissues known in smaller species of reptiles. Lizards, for example, have evolved to have detachable tails that can regrow, which they use to escape predators. But alligators are very large animals, potentially reaching up to 14 feet, and it was unknown how that difference in scale reflects on their regenerative abilities.

Taily tales

“The spectrum of regenerative ability across species is fascinating, clearly there is a high cost to producing new muscle,” said Jeanne Wilson-Rawls, co-senior author and associate professor with Arizona State University’s (ASU) School of Life Sciences.

“What makes the alligator interesting, apart from its size, is that the regrown tail exhibits signs of both regeneration and wound healing within the same structure,” said Cindy Xu, lead author of the paper. “Regrowth of cartilage, blood vessels, nerves, and scales were consistent with previous studies of lizard tail regeneration from our lab and others,” she said. “However, we were surprised to discover scar-like connective tissue in place of skeletal muscle in the regrown alligator tail.”

Alligators and humans both belong to the amniote group, related species who all have a spine or backbones. Lizards do, as well. Understanding more about the natural regeneration processes of these species could point the way towards better ways of repairing our own bodies after damage.

By studying the anatomy and tissue organization of regrown alligator tails, the team found that they were made up of a central skeleton of cartilage surrounded by connective tissue. The tails were fully irrigated with blood vessels and had nerve bundles, meaning they were fully-functional tails. The sheer scale and complexity of these regrown body parts after were surprising, the team adds, and goes a long way towards our understanding of regeneration processes in larger amniotes. It also raises questions about the history of such processes, and about their possibilities in the future.

For example, the team notes that alligators and birds both split off from dinosaurs around 250 million years ago, but birds lost their ability to regenerate while alligators did not. We’re not exactly sure when, or why, this happened. The authors note that existing literature makes no mention of dinosaur fossils with regrown tails.

But perhaps of more immediate concern for most of us is whether the findings have practical use. The team says it lays the groundwork for new therapies meant to heal wounds or treat diseases such as arthritis.

“If we understand how different animals are able to repair and regenerate tissues, this knowledge can then be leveraged to develop medical therapies,” said Rebecca Fisher, co-author of the paper.

The paper “Anatomical and histological analyses reveal that tail repair is coupled with regrowth in wild-caught, juvenile American alligators (Alligator mississippiensis)” has been published in the journal Scientific Reports.

A robot near you might soon have a tail to help with balance

New research from the Beijing Institute of Technology wants to steal the design of one of nature’s best balancing devices — the tail — and put it in robots.

A schematic outlining the design of the self-balancing robot tail. Image credits Zhang, Ren & Cheng.

Nature has often faced the same issues that designers and engineers grapple with in their work, but it has had much more time and resources at its disposal to fix them. So researchers in all fields of science aren’t ashamed of stealing some of its solutions when faced with a dead end. Over the past decades, roboticists have routinely had issues in making their creations keep their balance in any but the most ideal of settings. The humble tail might help break that impasse.

Tail tale

The bio-inspired, tail-like mechanism developed by the team can help their robot maintain balance in dynamic environments, the authors explain. The bot is made up of the main body, two wheels, and the tail component. This latter one is controlled by an “adaptive hierarchical sliding mode controller”, a fancy bit of code that allows it to rotate in different directions in an area parallel to the wheels.

In essence, it calculates and implements the tail motions needed to ensure the robot remains stable while moving around its environment.

There’s obviously some very complex math involved here. The authors explain that their system uses estimates of uncertainty in order to guide the tail. This is based on a theorem called the Lyapunov stability theorem, a theoretical framework that describes the stability of systems in motion. The tail then moves in specific patterns that are designed to increase the robot’s stability.

Most approaches to the issue of balancing two-wheeled vehicles today rely on collecting a vehicle’s body altitude data using an inertial measurement unit (IMU), a device that can measure forces acting on the robot’s body. This data is then processed and the results are used to determine a balancing strategy, which typically involves adjusting the robot’s tilt. These, the authors explain, typically work well enough — but they wanted to offer up an alternative that doesn’t involve tilting the robot’s body.

So far, the tail’s performance has only been evaluated in computer simulations, not in physical ones. However, these found it to be “very promising”, as it was able to stabilize a simulated robot who lost its balance within around 3.5 seconds. The team hopes that in the future, their tail will be used to make new or preexisting robot designs even more stable

The authors are now working on a prototype of the robot so that they can test its performance.

The paper “Control and application of tail-like mechanism in self-balance robot” has been published in the Proceedings of 2020 Chinese Intelligent Systems Conference.

Arque tail.

Robotic, seahorse-inspired tail can help people maintain balance through sickness or hard work

Three graduates from Keio University’s (Japan) graduate school of media design have created a bio-inspire robotic tail — that you can wear.

Arque tail.

Arque, the new robotic tail.
Image via Youtube / yamen saraiji.

If you’ve ever envied your pet‘s tail, Junichi Nabeshima, Yamen Saraij, and Kouta Minamizawa have got you covered. The trio designed an “anthropomorphic” robotic tail based on the seahorse’s tail that they chirstened ‘Arque’. The device could help extend body functions or help individuals who need support to maintain balance.

Tail-ored for success

Most animals rely on their tails for mobility and balance. While our bodies lack the same ability, the team hopes that Arque can help provide it. The authors explain in their paper that “the force generated by swinging the tail” can change the position of a person’s center of gravity. “A wearable body tracker mounted on the upper body of the user estimates the center of gravity, and accordingly actuates the tail.”

The tail is constructed out of several individual artificial vertebrae around a set of four pneumatic muscles. The team notes that they looked at the tail of seahorses for inspiration when designing the tail’s structure.

“In this prototype, the tail unit consists of a variant number of joint units to produce,” the trio told The Telegraph. “Each joint consists of four protective plates and one weight-adjustable vertebrae.”

“At each joint, the plates are linked together using elastic cords, while the vertebrae are attached to them using a spring mechanism to mimic the resistance to transverse deformation and compressibility of a seahorse skeleton, and also to support the tangential and shearing forces generated when the tail actuates.”

Arque’s modular design means that its length and weight can be adjusted to accommodate the wearer’s body. Apart from helping patients with impaired mobility, the tail could also be used in other applications, such as helping to support workers when they’re moving heavy loads.

The team also has high hopes for Arque to be used for “full-body haptic feedback”. Just as the tail can be used to change the center of mass and rebalance a user’s posture, it can be employed to generate full body forces (depending on where it’s attached to the body) and throw them off balance — which would help provide more realism to virtual reality interactions.

Arque’s intended use is to be worn, but one has to take into account personal experience and social interactions when predicting whether this will work or not. How likely would it be for people to feel comfortable putting one on, or wearing them outside? Most people definitely enjoy gadgets but, as the smart-glasses episode showed us, they need to perceive it as ‘cool’ or they won’t ever succeed. Whether or not a robotic tail will ever be as socially acceptable as a cane remains to be seen but.

In the meantime, it definitely does look like a fun tail to try on.

The tail was presented at the SIGGRAPH ’19 conference in Los Angeles. A paper describing the work “Arque: Artificial Biomimicry-Inspired Tail for Extending Innate Body Functions” has been published in the ACM SIGGRAPH 2019 Emerging Technologies journal.

A Hubble Space Telescope view of asteroid 6478 Gault, showing two comet-like tails of debris. Credit: European Southern Observatory.

Astronomers spy self-destructing asteroid with a twin comet-like tail

A Hubble Space Telescope view of asteroid 6478 Gault, showing two comet-like tails of debris. Credit: European Southern Observatory.

A Hubble Space Telescope view of asteroid 6478 Gault, showing two comet-like tails of debris. Credit: European Southern Observatory.

Almost 214 million miles (344 million km) from the sun, an asteroid is doing its best comet-like impression. Astronomers at the University of Hawaii have discovered an asteroid that is spinning itself into pieces, generating two debris tails of dust in the process.

First discovered in 1988, the first signs that the asteroid was self-destructing came on January 5. Using NASA’s Hubble Space Telescope, along with a variety of ground-based instruments in Hawaii, Spain, and India, astronomers found two debris tails trailing 6478 Gault in the main asteroid belt between Mars and Jupiter.

“This self-destruction event is rare,” Olivier Hainaut, of the European Southern Observatory in Garching, Germany, and co-author of the report said. “Active and unstable asteroids such as Gault are just now being detected because of new survey telescopes that scan the entire sky, which means asteroids that are misbehaving such as Gault cannot escape detection anymore.”

The observations are the first pieces of evidence of Gault’s misbehavior and suggest that asteroids are dynamic and can ultimately disintegrate due to the long-term subtle effect of sunlight, which can slowly spin them up until they begin to shed material. In Gault’s case, the asteroid is doing a speedy rotation every two hours, so fast that Gault is flinging material off its surface and into the void.

“Gault is the best ‘smoking-gun’ example of a fast rotator right at the two-hour limit,” said the University of Hawaii’s Jan Kleyna. “It could have been on the brink of instability for 10 million years. Even a tiny disturbance, like a small impact from a pebble, might have triggered the recent outbursts.”

Hubble revealed the tails to be narrow streamers, indicating that the dust was released in short bursts, lasting anywhere from a few hours to a few days. These sudden events puffed away enough debris to make a “dirt ball” approximately 500 feet (150 meters) across if compacted together. One tail was found to be approximately 500,000 miles (800,000 km) long by 3,000 miles (4,800 km) wide. The smaller tail spans about 125,000 (200,000 km) long.

Watching an asteroid come unglued like Gault gives astronomers the opportunity to study the makeup of asteroids without sending a spacecraft for samples. Analyzing an asteroid’s ingredients as they are spread out into space can offer astronomers a glimpse into planet formation in the early solar system.

“We didn’t have to visit Gault,” explained Hainaut. “We just had to look at the image of the streamers, and we can see all of the dust grains sorted neatly by size. All the large grains (about the size of sand particles) are close to the object and the smallest grains (about the size of flour) are the farthest away, because they are being pushed fastest by pressure from sunlight.”

Scientists turn the clock back 350 million years to show how humans lost their tails. Twice

Credit: Wikia.

We might not wag our tails anymore but humans still bear vestigial traces of one. Inside the uterus, human embryos start off with a tail that gradually disappears and once we come into this world, there’s a tailbone to remind us that we haven’t gone that far. Strikingly, our early ancestors lost their tails not once, but twice, say scientists who analyzed 350-million-year-old fossils.

To get to the bottom of things, researchers at the University of Pennsylvania analyzed the fossilized hatchlings of the Aetheretmon, a jawed fish and ancestor to terrestrial animals. The Aetheretmon used to have both a fleshy tail and a flexible tail fin, one sitting atop the other, the analysis showed.

Human embryos have a prenatal tail.

Human embryos have a prenatal tail.

Since Darwin, biologists thought fish simply grew their flexible tail atop an ancestral tail that’s shared with all land animals. But the new study overturns this thinking because the two tails are grown together. What really happened, the study‘s authors say, is fish lost their fleshy tail and kept only the tail fin, which is flexible and more adapted to aquatic environments. Then, those fish which gradually became semi-aquatic and then land dwelling lost their flexible fin tail and kept the fleshy tail. So we’re looking at two different modes altogether.

“Fleshy tails go all the way back to the earliest vertebrate ancestors and are found in very young embryos, so it would be very difficult to get rid of them entirely without causing other problems,” author Lauren Sallan told Seeker. “As a result, both fishes and humans have had to stunt growth instead, leaving a buried, vestigial tail much like the legs of whales.”

Losing the tail fin was strike one. Strike two happened once human ancestors lost what remained of their bony tail to accommodate upright movement. In both fish and humans, however, we can still see the remnants of the bony tail buried in our lower backs — the coccyx or tailbone.

“The tetrapod tail likely started as a limb-like outgrowth in the first vertebrates, while the fish caudal fin started as a co-opted median fin, like the dorsal fin,” Sallan said in a statement. “All vertebrate tail diversity might be explained by the relative growth and loss of these two tails, with the remaining fleshy tail stunted in humans as in fishes.”

It seems likely that the two outgrowths are governed by two different groups of genes. This would imply that natural selection affected them independently.

“It tells us why we have all this diversity in fins and limbs in past and present,” Sallan said. “There might have been some lineages that favored one form over another for functional or ecological reasons. If a fish couldn’t adapt this trait, which is so vital for swimming, they might have gone extinct.”

This study is not the last word on the matter, though. The findings have to be confirmed by a developmental biologist by verifying the molecular pathways that generate limb outgrowth.

“This would be an easy way of testing evolution in the lab,” she said.

Scientists find how lizards regenerate their tails

It’s one of the most remarkable adaptations in the animal world – growing a tail or a limb. Some lizards do it, salamanders do it, and by learning how they do it, we may soon be able to do it as well; with technology, that is.

The green anole lizard (Anolis carolinensis) can lose and then regrow its tail, using cartilage and fat to replace the bone.

A team of researchers have discovered the genetic “recipe” for lizard tail regeneration which, at the very basic level, comes down to the right combination and quantity of genes. To make things even more interesting, we humans have the same genes used in tail regrowth, so the study has a lot of potential.

“Lizards basically share the same toolbox of genes as humans,” said lead author Kenro Kusumi, professor in ASU’s (Arizona State University) School of Life Sciences and associate dean in the College of Liberal Arts and Sciences. “Lizards are the most closely-related animals to humans that can regenerate entire appendages. We discovered that they turn on at least 326 genes in specific regions of the regenerating tail, including genes involved in embryonic development, response to hormonal signals and wound healing.”

The interdisciplinary team studied how the green anole lizard, Anolis carolinensis, can lose its tail when attacked by a predator and then regrow it back. They used next-generation molecular and computer analysis tools to examine the genes turned on in tail regeneration. They found that lizards have quite an unique lengthy pattern of tail regeneration, different to what salamanders do, for example.

“Regeneration is not an instant process,” said Elizabeth Hutchins, a graduate student in ASU’s molecular and cellular biology program and co-author of the paper. “In fact, it takes lizards more than 60 days to regenerate a functional tail. Lizards form a complex regenerating structure with cells growing into tissues at a number of sites along the tail.”

Lizards don’t regenerate the bone in the tail – instead, the bone is replaced by cartilage and fat, losing some of its flexibility and power. But if this growing technique were to be applied in humans, substitutes could be used. The key here was identifying the genetic pathway that enables regeneration – and that’s exactly what scientists did.

“We have identified one type of cell that is important for tissue regeneration,” said Jeanne Wilson-Rawls, co-author and associate professor with ASU’s School of Life Sciences. “Just like in mice and humans, lizards have satellite cells that can grow and develop into skeletal muscle and other tissues.”

“Using next-generation technologies to sequence all the genes expressed during regeneration, we have unlocked the mystery of what genes are needed to regrow the lizard tail,” said Kusumi. “By following the genetic recipe for regeneration that is found in lizards, and then harnessing those same genes in human cells, it may be possible to regrow new cartilage, muscle or even spinal cord in the future.”

The team hopes their findings will one day be applied to medical situations such as spinal cord injuries, birth defects or arthritis.

Source: Arizona State University.


Carnotaurus had puny arms, incredibly powerful tail

If you think that T-Rex had laughable front limbs, you’re in for a treat: even he would be amused by upon such puny arms. However, the shortcomings Carnotaurus had more than made up for its very muscular and powerful tail, which made it one of the fastest hunters to ever walk the face of the Earth.

Measuring over 8 meters long, Carnotaurus ruled South America, while T-Rex was ‘in charge’ of Asia and North America; the dinosaur had razor sharp teeth that fitted in quite nicely with its amazing hunting abilities. Tail bone fossils reveal that a particular muscle known as the caudofemoralis was attached by a tendon to the upper leg bones; when the tail moved, it gived a momentum to the back legs, which led to remarkable and fearsome strides – a feat it wouldn’t have been capable otherwise.

Brian Murphy from the University of Alberta conducted the study. His examination of the tail showed that along its length were pairs of tall rib-like bones that interlocked with the next pair in line. Using 3-D computer models, Persons recreated the tail muscles of Carnotaurus. He found that the unusual tail ribs supported a huge caudofemoralis muscle. The interlocked bone structure along the dinosaur’s tail did present one drawback: the tail was rigid, making it difficult for the hunter to make quick, fluid turns. Persons says that what Carnotaurus gave up in maneuverability, it made up for in straight ahead speed. For its size, Carnotaurus had the largest caudofemoralis muscle of any known animal, living or extinct.

Via io9

Gecko tail has a mind of its own

geckoThe (awesome) ability of geckos and other related reptiles to shed their tale when endangered by predators has been known for a long time, but scientists know little about the movement, and especially what controls the movement of the tail once it’s separated from the tail. Anthony Russell of the University of Calgary and Tim Higham of Clemson University in South Carolina put a lot of time and effort into solving this mystery.

What’s interesting is that after it separates from the body, the tail does not only have rhythmic movement, but also flips, jumps and lunges, exhibiting a complicated movement pattern. Studying and understanding this behavior could be extremely useful for further spinal cord studies.

“Much is known about the ecological ramifications of tail loss, such as distracting predators, storing energy reserves and establishing social status but little is known about the pattern and control of movement of automized gecko tails,” says Russell a biological sciences professor at the U of C. “What we’ve discovered is that the tail does not simply oscillate in a repetitive fashion, but has an intricate repertoire of varied and highly complex movements, including acrobatic flips up to three centimetres in height.”

However, this is just the first step, and more efforts should be put into this research.

“An intriguing, and as yet unanswered, question is what is the source of the stimulus is that initiates complex movements in the shed tails of leopard geckos,” says Higham. “The most plausible explanation is that the tail relies on sensory feedback from the environment. Sensors on its surface may tell it to jump, pivot or travel in a certain direction.”