Tag Archives: great apes

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.

What does gestural communication of great apes tell us about human language?

Our language is one of the features that define us as human beings and distance us from all other animals. Though no other species has developed language like us, animals communicate with each other through a vast set of signals.

A chimpanzee asking for a snack from a keeper at Wellington Zoo, New Zealand. Image credits: Gabriel Pollard.

In the case of great apes, they communicate by vocalizations, facial expressions, body displays or gestures. Due to the phylogenetic proximity between humans and great apes, the study of gestural communication is particularly attractive since it allows to hypothesize how language evolved in our species. And the evolution of human language is one of the hardest scientific topics to do research. The reason is simple: language does not fossilize. That is why we are forced to look for other clues to enlight us about how our language evolved and great ape gestures can lead us much further in the search for answers than we previously thought.

First of all, great apes employ gestures in an intentional, flexible and goal-oriented ways and display them in various contexts like grooming, playing or feeding. For example, to request food, great apes usually use begging gestures in which they stretch their arms and open their hands towards other conspecific with food.

But why gestures can be considered as a precursor of human language? Well, neuroscience brought some interesting and strong findings but is not my intention discuss that kind of gestural theories based on brain data. Instead, I’m going to take a quick look at robust data collected during long-term field studies conducted in different study sites. Yeah, we already know that in our ontogenetic path, before we speak, we communicate to the world using gestures. In our species, gestures emerge first. Speech appears later. But this is not the proof that tickles my guts!

There is no doubt that great ape gestures are flexible. All scientific papers about primate gestural communication support this evidence. Same gesture for different purposes and different gestures for the same purpose. Pretty much similar to what we do with our spoken language. Different words for the same meaning and vice versa. So, we can highlight that apes communicate different things in very different situations.

One particular paper, written by Amy Pollick and Frans de Waal, reports an outstanding discovery: the gestural repertoire varies from group to group of the same species, in some kind of gestural dialect. Some gestures were only observed in particular circumstances and at one study site. Once again, pretty much similar to our language. Moreover, and in a broader view, Graham et al. (2017) made a diagram about gestural repertoires of chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) and these two great ape species share a very significant amount of gestures while some of them are unique to each species. Such striking overlap of gestures and, at the same time, the still more mind-blowing exclusivity of some gestures between chimpanzees and bonobos reveals us a scenario in which, most likely, the different languages of today evolved from an ancestral language. We are biologically programmed to speak but our language evolved itself in a cultural way, as apparently occurs with great ape gestures.

Furthermore, Hobaiter & Byrne (2014), focused on an attempt to translate the meaning of chimpanzee gestures. At the first glance, it may seem and exaggerated anthropocentric approach, trying to humanize all animal behavior. But for those who have spent many hours observing great apes gestural communication (like me), the similarities between human and great ape gestures pop out at you. So, in the paper cited above, the authors identified some gestures that sound us like “move away”, “please, groom me”, “stop that” or “follow me”.

Will be the great ape’s gestural communication the holy grail to understand the roots of human language? I guess so. The growing body of evidence that comes to us from primatological studies are quite exciting and it makes me very optimistic to solve the riddle of the evolution of our language. We need to keep collect data and test some hypothesis.

This is a guest post from Miguel Oliveira.


Pollick, A. S.; de Waal, F. B. M. (2007). Ape gestures and language evolution. PNAS, 104(19), 8184-8189;

Hobaiter, C.; Byrne, R. W. (2014). The meanings of chimpanzee gestures. Current Biology, 24(14), 1596-1600;

Graham, K. E.; Furuichi, T.; Byrne, R. W. (2017). The gestural repertoire of the wild bonobo (Pan paniscus): a mutually understood communication system. Animal Cognition, 20(2), 171-177;


Four out of six great apes are almost extinct because of us

While the situation of pandas is improving, the same can’t be said about great apes. According to the International Union for Conservation of Nature, the governing body of protected species, four of the six species of great apes are Critically Endangered – only one step away from going extinct. The remaining two are also under considerable threat of extinction.

Photo taken by Kabir Bakie at the Cincinnati Zoo July, 2005

Yes, it’s us

The Eastern Gorilla (Gorilla beringei), the largest living primate, has moved from Endangered to Critically Endangered after it lost 70% of its population in just 20 years. Furthermore, Grauer’s Gorilla (G. b. graueri), one subspecies of Eastern Gorilla – has lost 77% of its population since 1994. This decline was brought forth by humans, especially through hunting. These are our closest related animal relatives, and we’re killing them.

“To see the Eastern gorilla – one of our closest cousins – slide towards extinction is truly distressing,” says Inger Andersen, IUCN Director General. “We live in a time of tremendous change and each IUCN Red List update makes us realize just how quickly the global extinction crisis is escalating. Conservation action does work and we have increasing evidence of it. It is our responsibility to enhance our efforts to turn the tide and protect the future of our planet.”

Killing and hunting great apes is illegal, but that doesn’t seem to stop poachers. In 2013, a new report showed that nearly 3,000 chimpanzees, gorillas, bonobos, and orangutans are illegally killed or stolen from the wild each year, though the real figure is likely higher. Pair that off with habitat reduction, and survival becomes almost impossible.

“We are driving our closest living relatives to extinction, which is sickening,” said Dr Muttulingam Sanjanyan, vice-president at Conservation International.

According to him, local populations could greatly benefit from keeping the apes alive, but if we can’t do that, future generations will only see great apes in history books.

In many places of the world, especially in the ones richest in biodiversity, habitats are being destroyed at alarming paces, and the habitats of great apes are no exception. For most mammals, habitat destruction is the biggest problem, and this likely won’t stop anytime in the near future.

“Illegal hunting and habitat loss are still major threats driving many mammal species towards extinction,” says Carlo Rondinini, Coordinator of the mammal assessment at Sapienza University of Rome.

Many biologists believe we, as a society, are causing the planet’s sixth major extinction. An analysis conducted by Naturfound that 41% of all amphibians on the planet now face extinction while 26% of mammal species and 13% of birds are similarly threatened. The IUCN Red List now includes 82,954 species of which 23,928 are threatened with extinction.

This classy looking chap is a bonobo - a great ape species which is widely overlooked and often forgotten. A new research suggests bonobos are losing vital habitat due to both forest fragmentation and poaching. (c) Crispin Mahamba/Wildlife Conservation Society-DRC Program

New study adds new dimension to the threats posed to the Bonobo – the ‘forgotten ape’

This classy looking chap is a bonobo - a great ape species which is widely overlooked and often forgotten. A new research suggests bonobos are losing vital habitat due to both forest fragmentation and poaching. (c) Crispin Mahamba/Wildlife Conservation Society-DRC Program

This classy looking chap is a bonobo – a great ape species which is widely overlooked and often forgotten. A new research suggests bonobos are losing vital habitat due to both forest fragmentation and poaching. (c) Crispin Mahamba/Wildlife Conservation Society-DRC Program

The Bonobo, or Pygmy Chimpanzee as it was once called, is one of our closest relatives, yet one of the most poorly studied. This fascinating ape displays unique social order and other highly interesting traits, and unfortunately like all great apes it is also endangered. Very little is known, however, about how many specimens are there in the wild or how exactly threatened the bonobos currently are. In the most extensive study of its kind to date, a team of international scientists modeled bonobo habitat based on scarce and ready-available data in order to find what the true scale of these threats is. The results reveal that the bonobos are quickly running out of space and their habitat is far narrower and spaced apart than previously believed.

“This assessment is a major step towards addressing the substantial information gap regarding the conservation status of bonobos across their entire range,” said lead author Dr. Jena R. Hickey of Cornell University and the University of Georgia. “The results of the study demonstrate that human activities reduce the amount of effective bonobo habitat and will help us identify where to propose future protected areas for this great ape.”

“For bonobos to survive over the next 100 years or longer, it is extremely important that we understand the extent of their range, their distribution, and drivers of that distribution so that conservation actions can be targeted in the most effective way and achieve the desired results,” said Ashley Vosper of the Wildlife Conservation Society. “Bonobos are probably the least understood great ape in Africa, so this paper is pivotal in increasing our knowledge and understanding of this beautiful and charismatic animal.”

A great ape society based on love

One of mankind’s closest living relatives, the bonobos share more than 98% of our DNA or nearly as much as chimpanzees. Actually, they closely resemble chimpanzees with the key physiological distinction that they’re smaller hence the pygmy nickname. The similarities more or less end here though; while chimpanzees are loud, competitive and aggressive, the bonobo apes live in a peaceful, matriarchal and egalitarian society. In times of seldom conflict and tension or when promoting bonding or sharing alike, the bonobos choose to address all of these through sexual behavior. Like in human society, for Bonobos sex transcends reproduction and is seen as a means of expression and passionate caring. With this in mind, bonobos serve as a powerful symbol of peace and cooperation. Unfortunately, these great apes are listed as highly endangered, according to the  IUCN Red List.

Bonobos, like their chimpanzee cousins, live in “fission-fusion” societies and therefore tend to vary in party size. Communities of up to 100 bonobos will usually split into small groups when searching for food during the day and come back together to sleep at night. Also, bonobos are considered the most vocal of great apes as they frequently use complex vocal communication accompanied by hand gestures. Animal behaviorists believe these vocal fixtures play a pivotal role in bonobo society, helping them communicate with one another where favorite food sources are located, as well as the quality and preference of these foods function of vocal sequences.  The voice itself, or better said howl since it’s not articulated,  is quite pleasant to the human ear being melodic and high pitched, in contrast to the deeper and more guttural vocalizations of a chimpanzee.

This undated handout photo provided by Friends of Bonobos shows mother and a baby bonobo in the Congo. (c) Vanessa Woods/Duke University/AP

This undated handout photo provided by Friends of Bonobos shows mother and a baby bonobo in the Congo. (c) Vanessa Woods/Duke University/AP

Bonobos live only within the lowland forests of the Democratic Republic of Congo; a country beset by war, filled with corruption and where sadly poachers have their way. Previously, it was thought they inhabit approximately 500,000 square kilometers (193,000 square miles) of tropical forest south of the Congo River and north of the Kasai River, where the average rainfall is between 63 and 80 inches per year. This latest assessment shows, however, that bonobo range has dwindled greatly.

It’s impossible for the researchers to check every bonobo nest in the country, but what they attempted to do is the next best thing: create a model. Based on data of bonobo nest locations collected by numerous organizations between the years 2003-2010, the researchers identified 2364 “nest blocks,” with a block defined as a 1-hectare area occupied by at least one bonobo nest. Where nests weren’t identified in a region before, these interpolated based on previous data. The group then tested a number of factors that addressed both ecological conditions (describing forests, soils, climate, and hydrology) and human impacts (distance from roads, agriculture, forest loss, and density of “forest edge”) and produced a spatial model that identified and mapped the most important environmental factors contributing to bonobo occurrence.

Just a quarter of bonobo range is suitable

Results showed that the most obvious marker that skewed bonobo presence was human intervention through agriculture. The major takeaway that the study offers however is that only 28 percent of the bonobo range is classified as suitable for the great ape, and of these suitable area only 27.5 percent of it is located in existing protected areas. So technically, only a quarter of the bonobo range is actually suitable for them.

“Bonobos that live in closer proximity to human activity and to points of human access are more vulnerable to poaching, one of their main threats,” said Dr. Janet Nackoney, a Research Assistant Professor at University of Maryland and second author of the study. “Our results point to the need for more places where bonobos can be safe from hunters, which is an enormous challenge in the DRC.”

Dr. Nate Nibbelink, Associate Professor at the University of Georgia, added: “The bonobo habitat suitability map resulting from this work allows us to identify areas that are likely to support bonobos but have not yet been surveyed, thereby optimizing future efforts.”

“By examining all available data provided by a team of leading researchers, we can create the kind of broad-scale perspective needed to formulate effective conservation plans and activities for the next decade,” said Dr. Hjalmar S. Kühl of the Max Planck Institute for Evolutionary Anthropology.

“The fact that only a quarter of the bonobo range that is currently suitable for bonobos is located within protected areas is a finding that decision-makers can use to improve management of existing protected areas, and expand the country’s parks and reserves in order to save vital habitat for this great ape,” said Innocent Liengola, WCS’s Project Director for the Bonobo Conservation Project and co-author on the study.

Hopefully, with this new found knowledge at hand, conservation efforts spearheaded by NGOs and the local government might help save the bonobos and offer them the minimum decency and respect any living being deserves by not invading their homes.

“The future of the bonobo will depend on the close collaboration of many partners working towards the conservation of this iconic ape,” said Dr. Liz Williamson of the IUCN/SSC Primate Specialist Group and coordinator of the action planning process which instigated the bonobo data compilation for this study.

The results were reported in a paper published in the journal Biodiversity and Conservation. The team was comprised of researchers from the University of Georgia, University of Maryland, the Wildlife Conservation Society, ICCN (Congolese Wildlife Authority), African Wildlife Foundation, Zoological Society of Milwaukee, World Wildlife Fund, Max Planck Institute, Lukuru Foundation, University of Stirling, Kyoto University, and other groups.