̽��ֱ�� of Cambridge - primates

Tree-dwelling mammals survived after asteroid strike destroyed forests

cmm201 — Thu, 14 Oct 2021 12:10:32 +0000

Overall, the study supports the hypothesis that the widespread destruction of forests following the asteroid’s impact favoured ground-dwelling mammals over their arboreal counterparts. However, it also provides strong evidence that some tree-dwelling animals also survived the cataclysm, possibly nesting in branches through the Cretaceous-Paleogene (K-Pg) extinction event.

“ ̽��ֱ��recovery of terrestrial vertebrate life following the end-Cretaceous asteroid impact was one of the most important events in the history of life on Earth,” said senior author Dr Daniel Field, from Cambridge’s Department of Earth Sciences. “In this study, we drew on our previous work at Cambridge to investigate whether there were similarities in the ecological attributes of avian and mammalian survivors of the end-Cretaceous mass extinction.”

̽��ֱ��K-Pg mass extinction event occurred when a meteor slammed into Earth at the end of the Cretaceous period. ̽��ֱ��impact and its aftereffects killed roughly 75% of the animal and plant species on the planet, including whole groups like the non-avian dinosaurs.

For the study, the researchers analysed patterns of substrate preferences among all modern mammals and their ancestors, working backwards from the present day to before the K-Pg extinction event by tracing these traits along numerous phylogenetic trees — diagrams that illustrate the evolutionary relationships among species.

“Our study takes advantage of an ongoing revolution in our understanding of the tree of life, only made possible by researchers working in association with natural history collections,” said co-lead author Jacob Berv, from the ̽��ֱ�� of Michigan, USA. “By integrating data from such collections with modern statistical techniques, we can address new questions about major transitions in evolutionary history.”

̽��ֱ��researchers classified each mammalian species as arboreal, non-arboreal, or semi-arboreal. To be considered arboreal, the species had to nearly always nest in trees. Categorising some species could be tricky. For example, many bat species spend a lot of time among trees but nest in caves, so bats were mostly categorised as non-arboreal or semi-arboreal.

“We were able to see that leading up to the K-Pg event, there was a spike in transitions from arboreal and semi-arboreal to non-arboreal habitat use across our models,” said co-lead author Jonathan Hughes, from Cornell ̽��ֱ��, USA.

̽��ֱ��work builds on a previous study led by Field, which used the same analytical method — known as ancestral state reconstruction — to show that all modern birds evolved from ground-dwelling ancestors after the asteroid strike.

“ ̽��ֱ��fossil record of many vertebrate groups is sparse in the immediate aftermath of the extinction,” said Field, who is also curator of ornithology at the Cambridge Museum of Zoology. “Analytical approaches like ancestral state reconstruction allow us to establish hypotheses for how groups like birds and mammals made it through this cataclysm, which palaeontologists can then test when additional fossils are found.”

̽��ֱ��analysis helps illuminate ecological selectivity of mammals across the K-Pg boundary despite the relatively sparse fossil record of mammalian skeletal elements from the periods immediately preceding and following the asteroid’s impact.

How the tree-dwelling ancestors of primates survived the asteroid’s destruction is unclear. According to the authors, it’s possible that some forest fragments survived the calamity or that early primates and their relatives were ecologically flexible enough to modify their substrate preferences in a world mostly denuded of trees.

Reference:
Jonathan J Hughes et al. ‘Ecological selectivity and the evolution of mammalian substrate preference across the K–Pg boundary.’ Ecology and Evolution (2021). DOI: 10.1002/ece3.8114

Adapted from a Yale news release.

An asteroid strike 66 million years ago wiped out the non-avian dinosaurs and devastated the Earth’s forests, but tree-dwelling ancestors of primates may have survived it, according to a new study published in the journal Ecology and Evolution.

̽��ֱ��recovery of terrestrial vertebrate life following the end-Cretaceous asteroid impact was one of the most important events in the history of life on Earth

Daniel Field

Rod Waddington

Chimpanzee, Uganda

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Final biomedical trial on captive chimpanzees is first oral Ebola vaccine for saving wild apes

fpjl2 — Thu, 09 Mar 2017 12:06:41 +0000

̽��ֱ��results from the final biomedical research trial on captive chimpanzees for the foreseeable future have been published today in the journal Scientific Reports.

̽��ֱ��trial was of a vaccination for Ebola: the first orally administered vaccine for any disease developed specifically for the purpose of conserving wild apes.

In addition to poaching and forest loss, diseases such as Ebola and anthrax have devastated wild ape populations. Ebola alone is estimated to have killed one third of the world’s wild gorillas over the last three decades.

Now, new findings have shown an effective oral vaccine for Ebola in chimpanzees, and that the captive animals involved in the trial exhibited very few signs of stress as a result. Researchers say the work demonstrates a model that could be harnessed for other diseases and ape species in the wild.

However, after decades using chimpanzees to test vaccines destined for humans, changes in the law have seen enforced retirement of captive populations and the closing of chimpanzee research facilities in the US – the last developed country where biomedical testing on chimpanzees was legal.

In what researchers describe as a “horrible irony”, they say these reforms – a victory for long-standing campaigns by animal welfare groups – will ultimately prove detrimental to chimpanzees and gorillas in the wild, as any vaccination for wild animals must be tested in captivity first to ensure its safety.

Consequently, the promising new vaccine model may never progress to the point where it can be used to inoculate endangered wild apes, say the research team from the universities of Cambridge, UK, and Thomas Jefferson and Louisiana, US.

“In 2014 the world was gripped by fears of an Ebola virus pandemic. Yet few people realise that Ebola has already inflicted pandemic scale mortality on our closest relatives,” says lead researcher Dr Peter Walsh from the ̽��ֱ�� of Cambridge.

“African apes are also threatened by naturally occurring pathogens like anthrax, and the increasing overspill of human pathogens such as measles. A glimmer of hope lies in the fact that many of the disease threats are now vaccine preventable.

“We have developed a very promising tool for inoculating ape species against the myriad deadly diseases they face in the wild, but continued progress relies on access to a small number of captive animals.

“This may be the final vaccine trial on captive chimpanzees: a serious setback for efforts to protect our closest relatives from the pathogens that push them ever closer to extinction in the wild.”

Previous attempts to vaccinate wild apes have resorted to administering individual animals with hypodermic darts – a laborious task feasible for only a small number of apes habituated to human approach. By contrast, oral vaccines encased in appealingly edible baits could be distributed across wild ape territories to inoculate large numbers over longer periods.

Such an approach has already proved successful in other species: almost eliminating fox rabies (and the consequent need to cull foxes) across continental Europe.

̽��ֱ��latest study was carried out with ten chimpanzees in one of the last remaining chimpanzee research facilities in the US in New Iberia, Louisiana. Six received the oral vaccine, while four were injected as a control group.

All the animals displayed a robust immunity without side effects after 28 days – when the trial was terminated due to new Endangered Species Act regulations banning biomedical research on chimpanzees.

Throughout the trial, scientists closely monitored animal behaviour and physiology for signs of severe stress. Other than very minor weight loss (2% of body mass), they say that signs of trauma were “entirely absent”.

“Some pressure groups argue that all research on captive chimpanzees is tantamount to torture, not just because of procedures but also due to confinement,” says Walsh.

“Enclosures and animal care are now of a very high standard, with chimpanzees housed in large social spaces. ̽��ֱ��modest traces of stress we detected during our trial were akin to the values observed in college students anticipating exams.”

Captive chimpanzee trials are technically still legal in the US in instances that benefit the species. However, Walsh says that the limited funds available for conservation research makes it unviable for biomedical facilities to retain populations, while zoos and sanctuaries are either “ideologically opposed” or unwilling to risk any public backlash from testing.

Further work to enhance the vaccine, such as ensuring effectiveness after exposure to high tropical forest temperatures, may now never get done due to the closure of captive chimpanzee facilities.

“In an ideal world, there would be no need for captive chimpanzees,” says Walsh. “But this is not an ideal world. It is a world where diseases such as Ebola, along with rampant commercial poaching and habitat loss, are major contributors to rapidly declining wild ape populations.

“Oral vaccines offer a real opportunity to slow this decline. ̽��ֱ��major ethical debt we owe is not to a few captive animals, but to the survival of an entire species we are destroying in the wild: our closest relatives.”

Oral vaccine offers hope for ape species ravaged by Ebola and other diseases, as it can be widely dispersed to save more wild animals. However, scientists say recent law changes on captive chimpanzee testing may stop the conservation work in its tracks.

This may be the final vaccine trial on captive chimpanzees: a serious setback for efforts to protect our closest relatives from the pathogens that push them ever closer to extinction in the wild

Peter Walsh

Matthias Schnell

One of the captive chimpanzees in the research trial receiving the oral Ebola vaccination

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Yes

Baboons watch neighbours for clues about food, but can end up in queues

fpjl2 — Wed, 20 Apr 2016 09:01:05 +0000

Latest research on social networks in wild baboon troops has revealed how the animals get information from each other on the whereabouts of food. However, once information reaches a high status baboon, subordinates often end up in a queue for scraps.

A new study, by researchers from the ̽��ֱ�� of Cambridge and the Zoological Society of London, shows how baboons monitor each other for changes in behaviour that indicate food has been found, such as hunching over to scoop it up.

This ‘socially learned’ information gets transmitted through proximity: those with more neighbours are more likely to spot when someone starts feeding. Once they do, baboons will head towards the food.

Information then starts to spread through the troop, as more baboons observe feeding behaviour or notice their neighbours moving in the direction of food. However, troop hierarchy ultimately kicks in – with the most dominant member in the vicinity, usually a male, wading in to claim the spoils.

At this point, surrounding baboons will often form what can appear to be a queue, to determine who gets to explore that patch of ground next.

These queues reflect the complex interactions within a baboon troop. ̽��ֱ��sequence of baboons in a queue depends on status – sometimes through birth-right – as well as social and familial relationships to the particular baboon occupying the food patch.

̽��ֱ��new research, published in the open access journal eLife, breaks down the transmission of social information through a baboon troop into three stages:

Acquiring information: observing behaviour that suggests food.
Applying information: exploring the food patch (even if no food is left).
Finally, exploiting information: actually getting to eat.

̽��ֱ��researchers used social networking models to show how being close enough to spot behaviour change is the only driver for acquiring knowledge.

When it comes to applying and exploiting social knowledge, however, the characteristics of individual baboons – whether its sex, status, boldness, or social ties in grooming networks – determine who gets to eat, or where they are in any queue that forms.

Baboon troops can be sizable, sometimes as many as 100 members, with the troops in the latest study numbering around 70. On average, less than 25% of a troop – around 10 individuals – acquired information of a food patch, with less than 5% of the troop actually exploiting it.

“Who actually gets to eat is only half the story,” says Dr Alecia Carter, from Cambridge’s Department of Zoology, who led the research.

“Just looking at the animals that capture the benefits of information, in this case food, doesn’t reflect the real pattern of how information transmits through groups. Many more animals acquire information, but are limited in their use of it for a variety of reasons.”

To conduct the study, researchers snuck handfuls of maize corn kernels, a high-energy baboon favourite (“like finding a stash of chocolate bars”) into the path of two foraging troops of wild chacma baboons in Tsaobis Nature Park, Namibia.

Once a troop member found the food, the researchers recorded the identities of baboons that spotted the animal eating, accessed the food patch, and got anything to eat.

Carter says that the best place for low-ranking baboons is often the peripheries, in the hopes of finding food and grabbing a few kernels before information spreads, and they are supplanted by the local dominant.

“ ̽��ֱ��more dominant a baboon is, the more spatially central in the troop they tend to be – as they can afford to be there. This provides more opportunities to gain information through the wider network,” says Carter.

Low-rankers that discover food will sometimes try to eat as stealthily or as quickly as they can, but, once a dominant has taken control of the food patch, a queue will often form. Grooming relationships to the feeding dominant can help a subordinate jump up a queue, although much of it is dictated by status.

For females, status is a birth-right that remains fixed throughout a baboon’s life. While human societies historically privilege the firstborn, in baboon troops maternal lineage is ranked by lastborn – with each new female baby replacing the last in terms of hierarchy.

Young males hold the same rank as their mother until they reach adolescence, usually around the age of six, and start asserting dominance through their bigger size, leading to shifts in status.

“It is relatively easy to collect dominance data, as baboons are constantly asserting dominance,” explains Carter. “Low-cost assertions of dominance, such as pushing an individual out of small patches of food, help to mitigate high-cost assertions, such as fights, and maintain the order.”

“However, baboons can mediate their status to a minor extent by having good grooming relationships, and low-ranking individuals have a slightly higher chance of applying and exploiting information if they are central in a grooming network. Over a lifetime of food opportunities, this may prove important for fitness.”

While baboons acquire information about food locations from watching others, they can also use social learning to see when that food is likely to be gone. Interestingly, the researchers found that males and females will often use this information in different ways.

“Baboons are highly vigilant, and constantly pay attention to what their neighbours are up to. When those in a food patch are sifting through dirt and clearly coming up empty-handed, most females will walk off, and won’t waste their time,” says Carter.

“Males on the other hand, particularly young males, are amazingly persistent, and will stay in a patch shifting sand around for a very long time in the hopes of finding a stray kernel.

“We hypothesise that, while males can afford to expend the energy, adult females are lactating or pregnant most of the time, so need to conserve their strength, and often end up using the information in a more practical way as a result.”

Baboons learn about food locations socially through monitoring the behaviour of those around them. While proximity to others is the key to acquiring information, research shows that accessing food depends on the complex hierarchies of a baboon troop, and those lower down the pecking order can end up queuing for leftovers.

̽��ֱ��more dominant a baboon is, the more spatially central in the troop they tend to be – as they can afford to be there

Alecia Carter

Baboon troop

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Monkeys regulate metabolism to cope with environment and rigours of mating season

fpjl2 — Wed, 20 Apr 2016 08:28:06 +0000

New research on male Barbary macaques indicates that these primates have a flexible metabolic physiology which helps them survive by changing the speed of chemical reactions within their bodies, and consequently levels of energy, depending on temperature and availability of food.

̽��ֱ��study also suggests that the metabolic rate of male macaques spikes dramatically during mating season, potentially providing a higher "aerobic capacity" at a point when males mate with multiple females a day, as well as fight other males for mating opportunities.

Levels of thyroid hormones start to build around a month before mating season, with these metabolism-predicting hormones doubling in some animals at the peak of the season. This is only the second time that changes in metabolic physiology in the run up to mating season have been seen in a vertebrate, the first being in house sparrows.

̽��ֱ��natural habitat of Barbary macaques, in the mountains of Morocco and Algeria, is one of the most extreme environments in which any non-human primate lives.

Temperatures in winter drop as low as -5 degrees centigrade, with deep snow covering the ground for months at a time. Summer temperatures can reach 40 degrees, with food and water becoming scarce.

Researchers say that the metabolic flexibility they have observed in macaques may be an echo in one of our primate cousins of a vital physiological mechanism that has allowed humans to adapt to the planet's extreme climates – from Saharan deserts to the Arctic.

"Barbary macaques increase and decrease cellular activity and energy consumption in order to respond to challenges of climate, sustenance and reproduction. In a sense, what happens at a macro level – animal behaviour – is reflected at a micro, cellular level," said lead author Dr Jurgi Cristóbal-Azkarate of Cambridge's Division of Biological Anthropology, who conducted the research with colleagues from the universities of Roehampton and Lincoln.

"Understanding the rules and mechanisms that govern key decisions such as energy allocation in existing primates is important in gaining insight into how our ancestors were able to thrive outside tropical Africa," he said.

"Our knowledge of traits that allowed hominins to adapt to new climatic conditions is practically restricted to those that leave a traceable fossil record. We currently have a very limited understanding of the importance of physiological mechanisms in human evolution. ̽��ֱ��Barbary macaques in the Atlas Mountains are an ideal model to help address this knowledge gap."

̽��ֱ��new findings are published today in the journal Biology Letters.

By collecting faeces dropped by the animals and analysing the samples, the researchers were able to assess levels of the thyroid hormone T3, which is known to provide an indicator of the 'basal' metabolic rate: the amount of energy expended to keep a body at rest.

̽��ֱ��thyroid has been shown to affect metabolism across multiple species, including humans, in whom underactive thyroids slow metabolic rates and can cause tiredness, weight gain and depression.

Samples were taken across a nine month period from adult males in two groups – one which has nearly half their food supplied by tourists, and one which has to rely only on the natural diet of foraging for plants and insects.

On average, the monkeys fed by tourists had levels of T3 that were 10% higher, suggesting that those on the natural diet had to conserve energy as well as forage for food. T3 levels also increased the longer animals in both groups had to spend foraging for food. This is in line with other findings in vertebrates showing that they reduce secretion of thyroid hormones to reduce metabolic rates and save energy when "nutritionally stressed".

As the area's climate went through its dramatic seasonal shifts, so too did the macaque metabolism. T3 levels dropped markedly from June to August, then began to rise as mating season approached in the early Autumn. While T3 dropped again after mating season, the levels stayed much higher during the harsh winter months.

"All mammals, and even more so primates, share a common physiology," said Cristóbal-Azkarate. "As with humans, Barbary macaques increase T3 production in winter. Metabolic rates increase in response to lower temperatures as a mechanism to generate more energy and consequently more heat."

Even rain affected T3 and metabolic rates, which increased in wet weather. Researchers say this may show the "high thermoregulatory cost of wet fur".

̽��ֱ��effect of the mating season on the macaques' T3 levels, and consequently their metabolic rates, was highly significant. At the height of the season, T3 levels of the males increased by an average of 80% between both groups. ̽��ֱ��average T3 increase in the wild feeding group was 98%.

"This was an unexpected and interesting finding, suggesting that males boost their metabolism in preparation for the energetic challenges both of mating and of competing with other males for access to females," said Cristóbal-Azkarate.

"Thyroid hormones are essential for sexual development and reproductive function in mammals – there is an important increase in T3 production during puberty, for example.

"To date, studies of male reproductive competition have focused almost exclusively on testosterone and stress hormones. However, our study suggests that there is a new player in the field of male reproductive competition: the thyroid, and metabolic rate."

Added Cristóbal-Azkarate: "This is the first time in which the effects of climate, nutrition and reproductive competition on thyroid hormone physiology have been studied simultaneously, in a naturalistic setting.

"By doing this, we have been able to learn about the way in which the flexibility of the metabolic physiology of Barbary macaques allows these primates – and perhaps other species, including humans – to balance the multiple energetic demands of their harsh and highly variable environment, and cope with ecological and social challenges."

̽��ֱ��flexible physiology of Barbary macaques in responding to extreme environmental conditions of their natural habitat may help shed light on the mechanisms that allowed our ancestors to thrive outside Africa, say researchers. New study also presents the first evidence for male primates boosting their metabolic physiology for mating.

Understanding the rules and mechanisms that govern key decisions such as energy allocation in existing primates is important in gaining insight into how our ancestors were able to thrive outside tropical Africa

Jurgi Cristóbal-Azkarate

NHK photo by Michael J. Sanderson/Ateles Films

Barbary Macaques in their natural habitat of the Atlas Mountains

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Yes

Calls vs. balls: monkeys with more impressive roars produce less sperm

fpjl2 — Thu, 22 Oct 2015 16:02:52 +0000

Howler monkeys are about the size of a small dog, weighing around seven kilos, yet they are among the loudest terrestrial animals on the planet, and can roar at a similar acoustic frequency to tigers.

Evolution has given these otherwise lethargic creatures a complex and powerful vocal system. For males, a critical function of the roar is for mating: to attract females and scare off rival males.

But not all male howler monkeys have been equally endowed. New research on howler species has revealed an evolutionary “trade-off” between investments in the size of the male hyoid – the bulbous, hollow throat bone that allows the howlers’ guttural roar to resonate – and in the size of reproductive organs, namely the testes.

̽��ֱ��bigger a male howler’s vocal organ, and the deeper and more imposing roar they possess, the smaller their testes and the less sperm they can produce.

Researchers found that the trade-off corresponds to the mating systems of different howler species. Males with large hyoids and deeper roars but more diminutive testes live in small social groups with often only one male dominating a number of females – a “harem” social model.

Males with bigger testes and smaller hyoids live in large groups with up to five or six males, and females mate with all males in the group. These males don’t have exclusive access to females, and the battle for reproduction is geared more towards “sperm competition”: quantity and quality of sperm.

̽��ֱ��findings, published today in the journal Current Biology, are a further example of sexual selection say the researchers – a theory first proposed by Charles Darwin in 1871 – and in particular the evolutionary trade-off between “pre- and post-copulatory reproductive strategies”: traits that help males compete for access to mates versus those that help males compete to fertilise eggs.

“In evolutionary terms, all males strive to have as many offspring as they can, but when it comes to reproduction you can’t have everything,” said Dr Jacob Dunn, from the ̽��ֱ�� of Cambridge’s Division of Biological Anthropology, who led the new study.

“There is evidence in other animals that when males invest in large bodies, bright colours, or weaponry such as horns or long canines, they are unable to also invest in reproductive traits. However, this is the first evidence in any species for a trade-off between vocal investment and sperm production,” he said.

In biology, trade-offs are said to exist when one trait cannot increase without a decrease in another. However, Dunn says that it’s not yet clear exactly how the evolutionary trade-off in male howler monkeys works.

“It may be that investment in developing a large vocal organ and roaring is so costly that there is simply not enough energy left to invest in testes. Alternatively, using a large vocal organ for roaring may be so effective at deterring rival males that there is no need to invest in large testes,” he said.

Along with collecting data on the average testes size across howler species, the researchers also used 3-D laser scans to analyse the size of over 250 hyoids – finding a ten-fold variation from the smallest to the largest howler throat bone. ̽��ֱ��team also conducted in-depth acoustic analyses of a number of howler roars.

“ ̽��ֱ��vocal folds of a howler monkey are three times longer than in a human, yet they are ten times smaller than us, with a hyoid bone uniquely adapted to resonate sound and exaggerate their size,” said Dunn.

“ ̽��ֱ��results of our acoustic analyses show that howler monkeys produce roars at a similar frequency as tigers, which is far lower than we would have predicted from their body size, yet exactly what would be predicted from measuring their giant vocal folds.”

This vocal system means that howlers give the acoustic impression of animals with much larger bodies, and can indeed roar louder and deeper than creatures ten times their size. ̽��ֱ��unnerving sound of a howler chorus ringing out across forests of Central and South America has long fascinated humans – from ancient Mayans to modern primatologists – and can carry as far as five kilometres through dense rainforest.

Charles Darwin was fascinated by the “wonderfully powerful” vocal organs of the howler monkey, despite describing their chorus as a “dreadful concert” in ̽��ֱ��Descent of Man.

̽��ֱ��new Cambridge research continues to show just how accurate Darwin was when he wrote in On the Origin of Species: “ ̽��ֱ��whole organism is so tied together that when slight variations in one part occur, and are accumulated through natural selection, other parts become modified.”

Evolutionary ‘trade-off’ between size of throat and testes discovered in howler monkeys furthers Darwin’s theory of sexual selection and corresponds to mating systems: males with larger throats but smaller testes often have exclusive access to females, while those with larger testes share mates.

In evolutionary terms, all males strive to have as many offspring as they can, but when it comes to reproduction you can’t have everything

Jacob Dunn

Calls vs. balls: An evolutionary trade-off

Mariana Raño

A black howler monkey chorus

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Yes

Young male chimpanzees play more than females with objects, but do not become better tool users

fpjl2 — Wed, 07 Oct 2015 18:03:34 +0000

New research shows a difference between the sexes in immature chimpanzees when it comes to preparing for adulthood by practising object manipulation – considered ‘preparation’ for tool use in later life.

Researchers studying the difference in tool use between our closest living relatives, chimpanzees and bonobos, found that immature bonobos have low rates of object manipulation, in keeping with previous work showing bonobos use few tools and none in foraging.

Chimpanzees, however, are the most diverse tool-users among non-human primates, and the researchers found high rates of a wide range of object manipulation among the young chimpanzees they studied.

While in adult wild chimpanzees it is females that are more avid and competent tool users, in juvenile chimpanzees the researchers conversely found it was the young males that spent more time manipulating objects, seemingly in preparation for adult tool use.

“In numerous mammalian species, sex differences in immatures foreshadow sex differences in the behaviour of adults, a phenomenon known as ‘preparation’,” said Dr Kathelijne Koops, who conducted the work at the ̽��ֱ�� of Cambridge’s Division of Biological Anthropology, as well as at the Anthropological Institute and Museum at Zurich ̽��ֱ��.

Much of the time young male chimpanzees spent manipulating objects was dominated by ‘play’: with no apparent immediate goal, and often associated with a ‘play face’ – a relaxed expression of laughing or covering of upper teeth.

̽��ֱ��sex bias for object manipulation the researchers found in juvenile chimpanzees is also found in human children. “ ̽��ֱ��finding that in immature chimpanzees, like humans, object-oriented play is biased towards males may reflect a shared evolutionary history for this trait dating back to our last common ancestor,” write the researchers from Cambridge, Zurich and Kyoto, who studied communities of wild chimpanzees and bonobos in Uganda and Congo for several months, cataloguing not just all tool use, but all object manipulation.

Immature females, on the other hand, showed lower rates of object manipulation, especially in play, but displayed a much greater diversity of manipulation types than males – such as biting, breaking or carrying objects – rather than the play-based repetition seen in the object manipulation of immature males.

This seems to prepare the females better for future tool use. In an earlier study at Gombe (Tanzania), immature female chimpanzees were also observed to pay closer attention to their mothers using tools and became proficient tool users at an earlier age than males.

“Immature females seem to focus their attention on relevant tool use related tasks and thus learn quicker, whereas males seem to do more undirected exploration in play,” write the researchers.

They say they believe the findings show that not all object manipulation in juvenile chimpanzees is preparation for tool use, and the different types of object manipulation need to be considered.

̽��ֱ��researchers say that the apparent similarity between human children and young chimpanzees in the observed male bias in object manipulation, and manipulation during play in particular, may suggest that object play functions as motor skill practice for male-specific behaviours such as dominance displays, which sometimes involve the aimed throwing of objects, rather than purely to develop tool use skills.

However, the researchers also point out that further work is needed to disentangle possible functions of object manipulation during development.

“We found that young chimpanzees showed higher rates and, importantly, more diverse types of object manipulation than bonobos. Despite being so closely related on the evolutionary tree, as well as to us, these species differ hugely in the way they use tools, and clues about the origins of human tool mastery could lie in the gulf between chimpanzees and bonobos,” Koops said.

“We found that male chimpanzees showed higher object manipulation rates than females, but their object manipulation was dominated by play. Young female chimpanzees showed much more diverse object manipulation types,” she said.

“We suggest that the observed male bias in young chimpanzees may reflect motor skill practice for male-specific behaviours, such as dominance displays, rather than for tool use skills. It seems that not all object manipulation in immatures prepares for subsistence tool use. It is important to take the types of manipulation into consideration.”

̽��ֱ��researchers also found that in chimpanzees, but not bonobos, the types of objects manipulated became more tool-like as the apes age. “As young chimpanzees get older they switch to manipulating predominantly sticks, which in this community is the tool type used by adults to harvest army ants,” Koops explained.

This practice of ant ‘dipping’, when chimpanzees lure streams of insects onto a stick, then scoop them up by running a hand along the stick and into the mouth, provides a quick source of protein.

Koops added: “Given the close evolutionary relationship between chimpanzees, bonobos and humans, insights into species and sex differences in ‘preparation’ for tool use between chimpanzees and bonobos can help us shed light on the functions of the highly debated gender differences among children.”

̽��ֱ��research is published today in the journal PLOS ONE.

Research into differences between chimpanzees and bonobos in ‘preparation’ for tool use reveals intriguing sex bias in object manipulation in young chimpanzees – one that is partly mirrored in human children.

We found that male chimpanzees showed higher object manipulation rates than females, but their object manipulation was dominated by play

Kathelijne Koops

Kat Koops

Young chimpanzee playing with branches.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Tool use is 'innate' in chimpanzees but not bonobos, their closest evolutionary relative

fpjl2 — Tue, 16 Jun 2015 08:22:36 +0000

Chimpanzees and bonobos are the two closest living relatives of the human species - the ultimate tool-using ape. Yet, despite being so closely related on the evolutionary tree, wild chimpanzees and bonobos differ hugely in the way they use tools.

Chimpanzees show the most diverse range of tool use outside of humans. For example, chimpanzees use sticks to 'fish' for ants and termites, stones to crack nuts, as well as tools for grooming and communication. Bonobos rarely use tools and never to forage for food.

̽��ֱ��question of 'what makes a tool user?' is a key one in human evolution, says researcher Dr Kathelijne Koops, and the origins of human tool mastery could lie in the gulf between tool use in chimpanzees and bonobos.

Is it to do with the environment the apes live in and the surrounding opportunities for tool use? Or perhaps the opportunities to learn from other apes through social contact? Or something deep-rooted. Something intrinsic.

Koops, in collaboration with colleagues from Kyoto ̽��ֱ��, conducted painstaking research tracking communities of wild chimpanzees and bonobos in Uganda and Congo for months, cataloguing not just all tool use, but also all potential for tool use in terms of the different environments and social time spent.

They also investigated the innate propensity for object manipulation in young apes, regardless of whether said object was deployed as a 'tool' - the first wild inter-species comparison of its kind.

̽��ֱ��researchers found that environmental opportunities did not explain the difference in tool use. From nut trees to ant nests, stones to shrubs, the bonobos had access to as many tools and promising foraging opportunities in their stomping ground as the chimpanzees.

Nor did social opportunities. In fact, young bonobos spent more time with their mothers, and had more individuals in close proximity for more time whilst feeding than young chimpanzees. Young bonobos also had more social partners than young chimpanzees.

However, immature chimpanzees manipulated and played a lot more with objects than bonobos, and played with objects on their own. This was a difference already visible in very young individuals, says Koops. In fact, she says this is the first evidence for a species difference in the innate predisposition for tool use in our closest evolutionary cousins.

"Chimpanzees are object-oriented, in a way that bonobos are not," said Koops, who conducted the work at Cambridge ̽��ֱ��'s Division of Biological Anthropology and at Zurich ̽��ֱ��'s Anthropological Institute and Museum.

"Given the close evolutionary relationship between these two species and humans, insights into the tool use difference between chimpanzees and bonobos can help us identify the conditions that drove the evolution of human technology.

"Our findings suggest that an innate predisposition, or intrinsic motivation, to manipulate objects was likely also selected for in the hominin lineage and played a key role in the evolution of technology in our own lineage," she said.

̽��ֱ��research is published today in the journal Scientific Reports.

Inset image: Young Bonobos Engaged in Social Play. Credit: Kathelijne Koops

First evidence for a species difference in the innate predisposition for tool use in our closest evolutionary cousins could provide insight into how humans became the ultimate tool-using ape.

Insights into the tool use difference between chimpanzees and bonobos can help us identify the conditions that drove the evolution of human technology

Kathelijne Koops

A Young Chimpanzee Playing with Twigs

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Yes

Baboons prefer to spend time with others of the same age, status and even personality

sc604 — Wed, 13 May 2015 08:06:32 +0000

New research shows that chacma baboons within a troop spend more of their time with baboons that have similar characteristics to themselves: associating with those of a similar age, dominance rank and even personality type such as boldness. This is known as homophily, or ‘love of the same’.

A team of researchers led by the ̽��ֱ�� of Cambridge and international conservation charity the Zoological Society of London says that this may act as a barrier to the transfer of new social information to the wider troop, as previous research done by the team shows baboons of a certain age and personality type – the younger, bolder animals – are more likely to be information ‘generators’: those who solve new foraging problems.

Given that information generators spend much of their time in the company of similar baboons, researchers say there is a risk that acquired information may end up exclusively confined to other information generators, thus decreasing the likelihood of new knowledge being disseminated to the wider troop.

Research teams tracked the same two baboon troops from dawn until dusk across Namibia’s Tsaobis Nature Park over several months each year between 2009-2014 to observe patterns of behaviour. ̽��ֱ��study is the first to monitor baboon social network structures over such a timescale and is published today in the journal Royal Society Open Science.

“Within these big troop networks over time social preferences are generally dictated by age, rank, personality and so on,” said Dr Alecia Carter, from the ̽��ֱ�� of Cambridge’s Department of Zoology, first author of the study. “This happens in humans all the time; we hang out with people who have the same income, religion, education etc. Essentially, it’s the same in baboons.”

To test for the personality traits of ‘boldness’ – essentially an assertive curiosity – the researchers planted unfamiliar foods on the edge of paths commonly used by baboon troops. These stimuli included hard-boiled eggs and small bread rolls dyed red or green. ̽��ֱ��research team then measured the time spent on investigating the new foodstuff, and whether they ate it, to determine a scale of boldness for members of the baboon troops.

“Our analysis is the first to suggest that bolder and shyer baboons are more likely to associate with others that share this personality trait,” said Dr Guy Cowlishaw from the Zoological Society of London, senior author of the study. “Previous studies in other animals – from chimps to guppies – suggests that time spent in the company of those with similar personalities could promote cooperation among individuals.

“Why baboons should demonstrate homophily for boldness is unclear, but it could be a heritable trait, and the patterns we’re seeing reflect family associations.”

Perhaps surprisingly, says Carter, gender was not a particular obstacle to social interaction, with females preferring to groom males. This is, in part, due to the obvious sexual engagements for breeding, but also as a tactic on the part of females to curry favour with particular males for the sake of their offspring.

“Chacma baboon males will often commit infanticide, killing the babies of rivals. Female baboons try and get around this by being as promiscuous as possible to confuse the paternal identity – so males find it harder to tell if they are killing a rival’s offspring or their own,” added Dr Carter.

“They will also try and form bonds with particular males in the hope that they will protect their offspring and let the babies forage in good places with them – although males tend to be fairly lazy when it comes to this; it’s up to the babies to follow the males to good food.”

Latest research shows that, within large troops, baboons spend more time grooming those with similar dominance rank and boldness to themselves. Preferring such grooming partners may prevent new skills and knowledge being transmitted around the wider troop, say researchers.

This happens in humans all the time; we hang out with people who have the same income, religion, education etc. Essentially, it’s the same in baboons

Alecia Carter

Grooming

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes