Tag Archives: #monkey

Survival Of The Thickest: Big Brains Make Mammal Populations Less Dense (Biology)

Brain size shown to influence mammal abundance in local areas for the first time.

Mammals with big brains tend to be less abundant in local areas than those with smaller brains, new research has shown.

A Barbary macaque (Macaca sylvanus) in Gibraltar © Manuela Gonzalez-Suarez/University of Reading

The University of Reading led an international team of scientists in considering the effect of brain size for the first time in studying why populations densities of land mammals like mice, monkeys, kangaroos and foxes vary so widely in local areas, even among similar creatures.

Using statistical models to test different scenarios for hundreds of species, they found an overall trend of mammals with larger brains occurring at lower densities. Where different species had similar diets and body masses, brain size was found to be the deciding factor.

Dr Manuela González-Suárez, associate professor in ecological modelling at the University of Reading, who led the study, said: “Although they are associated with being smarter, we found that bigger brains may actually hold mammals back from becoming the most abundant organisms in an area. This may be because bigger brains require more food and other resources, and therefore more space, to sustain them.

“Understanding which animals are more abundant in different areas is important for conservation. Low densities make species more likely to become extinct, while higher local abundance can increase exposure to some threats like roads.

“Brain size is not the only thing that influences mammal abundance. Different environments have different levels of stability and competing species, so these will also have an impact. Further research is required to see how the effect of brain size varies in these different environments.

“There are also some exceptions to the rule. For example, humans appear to have used their advanced intelligence to overcome resource limitations, through agriculture and food production. We can import foods from halfway round the world to allow us to theoretically live almost anywhere in large numbers. Some other brainy species may also be able to partially overcome these limitations.”

Table showing the body and brain size and the abundance of some of the species studied by the researchers © University of Reading

Although body size and diet are known to influence population densities, scientists had previously disagreed over whether bigger brains increased population densities in local areas by allowing creatures to exploit new resources, or decreased them due to requiring additional resources.

In the new study, published in the Journal of Animal Ecology, the team tested the relationship between brain size, body mass, diet and population density for 656 non-flying terrestrial mammal species.

Analysis revealed larger mammals with bigger brains and specialised diets were likely to be less locally abundant. The trend was particularly strong for primates and meat-eating mammals, but less clear in rodents and marsupials.

Examples from the study included the Barbary macaque – the species of monkey found in Gibraltar – which has an average body weight of 11kg and a brain weighing 95g, and whose average population density is 36 individuals per square kilometre. This density is nearly three times greater than the siamang – a species of gibbon – which has the same average body weight and diet but a larger brain weighing 123g, and an average population density of 14 individuals per square kilometre.

Reference: González‐Suárez, M, Gonzalez‐Voyer, A, von Hardenberg, A, Santini, L. The role of brain size on mammalian population densities. J Anim Ecol. 2020; 00: 1– 9. https://besjournals.onlinelibrary.wiley.com/doi/10.1111/1365-2656.13397 https://doi.org/10.1111/1365-2656.13397

Provided by University of Reading

Monkey See Others, Monkey Do: How The Brain Allows Actions Based On Social Cues (Neuroscience)

Researchers at NIPS in Japan show that information flow between two regions in the front of the brain makes it possible for monkeys to correctly interpret social cues.

In baseball, a batter’s reaction when he swings and misses can differ depending on whether they were totally fooled by the pitch or simply missed the change-up they expected. Interpreting these reactions is critical when a pitcher is deciding what the next pitch should be. This type of socially interactive decision-making is the topic of a recent brain study led by Masaki Isoda at the National Institute for Physiological Sciences (NIPS) in Japan. They found that this ability requires a specific connection between two regions in the front of the brain, and that without it, monkeys default to making decisions as if they were playing against an inanimate object.

Information flow from PMv to MPFC is vital for making decisions based on social cues provided by other monkeys (left); when this neuronal pathway is silenced, monkeys cannot catch the social cues (right). ©Taihei Ninomiya.

Two regions in the front of the brain–the PMv and the mPFC–contain “self”, “partner”, and “mirror” neurons that signal self-actions, other-actions, or both, respectively. Scientists believe that these types of neurons are what make social qualities such as empathy possible. However, despite years of research, not much is known about how these brain regions work together. The NIPS team set out to find some answers.

They trained monkeys to play a game with a partner in which they pressed buttons to obtain rewards. Sometimes, the rules of the game changed, and the monkeys made mistakes. Sometimes monkeys made mistakes simply because they were careless. “Monkeys continued using the same rule if they thought the other monkey’s mistakes were accidental,” says Masaki Isoda. “But, if they thought the mistakes were because the rules had changed, the monkeys adjusted their thinking and switched rules.” The researchers included three types of partners: real monkeys, recorded monkeys, and inanimate objects.

They found that the proportion of partner cells was much higher in the mPFC than in the PMv, indicating it could be particularly important for understanding what others are thinking. Partner cells in the mPFC were most active and most affected by the PMv when partners were real and least active and least affected when they were inanimate objects. Thus, it seemed possible that the ability of a monkey to recognize social cues depends on mPFC cells getting social information from the PMv.

To test this hypothesis, the researchers used viral vector technology to temporally silence only neurons in the PMv that connect to the mPFC. In this situation, monkeys made many more mistakes after their partners made careless errors, behaving as if every error was because the rules had changed. “This behavior was reminiscent of an autistic monkey who played the same game,” says Taihei Ninomiya. “As difficulty understanding social cues is a hallmark of autism, understanding the role of the PMv-mPFC pathway provides a good direction for future research into autism spectrum disorders.”

References: Ninomiya, T., Noritake, A., Kobayashi, K. et al. A causal role for frontal cortico-cortical coordination in social action monitoring. Nat Commun 11, 5233 (2020). https://doi.org/10.1038/s41467-020-19026-y link: http://dx.doi.org/10.1038/s41467-020-19026-y

Provided by National Institute of Natural Sciences

Cognitive Elements of Language Have Existed for 40 Million Years (Language)

Humans are not the only beings that can identify rules in complex language-like constructions – monkeys and great apes can do so, too, a study at the University of Zurich has shown. Researchers at the Department of Comparative Language Science of UZH used a series of experiments based on an ‘artificial grammar’ to conclude that this ability can be traced back to our ancient primate ancestors.

The chimpanzees learned that certain sounds were always followed by other specific sounds, even if they were sometimes separated by other acoustic signals. (Image: Istock.com/Juanmonino)

Language is one of the most powerful tools available to humankind, as it enables us to share information, culture, views and technology. “Research into language evolution is thus crucial if we want to understand what it means to be human,” says Stuart Watson, postdoctoral researcher at the Department of Comparative Language Science of the University of Zurich. Until now, however, little research has been conducted about how this unique communication system came to be.

Identifying connections between words
An international team led by Professor Simon Townsend at the Department of Comparative Language Science of the University of Zurich has now shed new light on the evolutionary origins of language. Their study examines one of the most important cognitive elements needed for language processing – that is, the ability to understand the relationship between the words in a phrase, even if they are separated by other parts of the phrase, known as a “non-adjacent dependency”. For example, we know that in the sentence “the dog that bit the cat ran away”, it is the dog who ran away, not the cat, even though there are several other words in between the two phrases. A comparison between apes, monkeys and and humans has now shown that the ability to identify such non-adjacent dependencies is likely to have developed as far back as 40 million years ago.

Acoustic signals instead of words

The researchers used a novel approach in their experiments: They invented an artificial grammar, where sequences are formed by combining different sounds rather than words. This enabled the researchers to compare the ability of three different species of primates to process non-adjacent dependencies, even though they do not share the same communication system. The experiments were carried out with common marmosets – a monkey native to Brazil – at the University of Zurich, chimpanzees (University of Texas) and humans (Osnabrück University).

Mistakes followed by telltale looks
First, the researchers taught their test subjects to understand the artificial grammar in several practice sessions. The subjects learned that certain sounds were always followed by other specific sounds (e.g. sound ‘B’ always follows sound ‘A’), even if they were sometimes separated by other acoustic signals (e.g. ‘A’ and ‘B’ are separated by ‘X’). This simulates a pattern in human language, where, for example, we expect a noun (e.g. “dog”) to be followed by a verb (e.g. “ran away”), regardless of any other phrasal parts in between (e.g. “that bit the cat”).

In the actual experiments that followed, the researchers played sound combinations that violated the previously learned rules. In these cases, the common marmosets and chimpanzees responded with an observable change of behavior; they looked at the loudspeaker emitting the sounds for about twice as long as they did towards familiar combinations of sounds. For the researchers, this was an indication of surprise in the animals caused by noticing a ‘grammatical error’. The human test subjects were asked directly whether they believed the sound sequences were correct or wrong.

Common origin of language

“The results show that all three species share the ability to process non-adjacent dependencies. It is therefore likely that this ability is widespread among primates,” says Townsend. “This suggests that this crucial element of language already existed in our most recent common ancestors with these species.” Since marmosets branched off from humanity’s ancestors around 40 million years ago, this crucial cognitive skill thus developed many million years before human language evolved.

References: Stuart K. Watson, Judith M. Burkart, Steven J. Schapiro, Susan P. Lambeth, Jutta L. Mueller and Simon W. Townsend. Non-adjacent dependency processing in monkeys, apes and humans. Science Advances, 21, vol. 6, no. 43. October 2020. DOI: 10.1126/sciadv.abb0725

Provided by University of Zurich

Oldest Monkey Fossils Outside Of Africa Found (Paleontology)

Three fossils found in a lignite mine in southeastern Yunan Province, China, are about 6.4 million years old, indicate monkeys existed in Asia at the same time as apes, and are probably the ancestors of some of the modern monkeys in the area, according to an international team of researchers.

Reconstruction of M. pentelicus from Shuitangba ©Mauricio Antón

“This is significant because they are some of the very oldest fossils of monkeys outside of Africa,” said Nina G. Jablonski, Evan Pugh University Professor of Anthropology, Penn State. “It is close to or actually the ancestor of many of the living monkeys of East Asia. One of the interesting things from the perspective of paleontology is that this monkey occurs at the same place and same time as ancient apes in Asia.”

The researchers, who included Jablonski and long-time collaborator Xueping Ji, department of paleoanthropology, Yunnan Institute of Cultural Relics and Archaeology, Kunming, China, studied the fossils unearthed from the Shuitangba lignite mine that has yielded many fossils. They report that “The mandible and proximal femur were found in close proximity and are probably of the same individual,” in a recent issue of the Journal of Human Evolution. Also uncovered slightly lower was a left calcaneus — heel bone — reported by Dionisios Youlatos, Aristotle University of Thessaloniki, Greece, in another paper online in the journal, that belongs to the same species of monkey, Mesopithecus pentelicus.

Photograph of the fossilized jawbone of a Miocene monkey, M. pentelicus. ©Xueping Ji, Yunnan Institute of Cultural Relics and Archaeology.

“The significance of the calcaneus is that it reveals the monkey was well adapted for moving nimbly and powerfully both on the ground and in the trees,” said Jablonski. “This locomotor versatility no doubt contributed to the success of the species in dispersing across woodland corridors from Europe to Asia.”

The lower jawbone and upper portion of the leg bone indicate that the individual was female, according to the researchers. They suggest that these monkeys were probably “jacks of all trades” able to navigate in the trees and on land. The teeth indicate they could eat a wide variety of plants, fruits and flowers, while apes eat mostly fruit.

Fossilized heel bone of M. pentelicus ©Xueping Ji, Yunnan Institute of Cultural Relics and Archaeology

“The thing that is fascinating about this monkey, that we know from molecular anthropology, is that, like other colobines (Old World monkeys), it had the ability to ferment cellulose,” said Jablonski. “It had a gut similar to that of a cow.”

These monkeys are successful because they can eat low-quality food high in cellulose and obtain sufficient energy by fermenting the food and using the subsequent fatty acids then available from the bacteria. A similar pathway is used by ruminant animals like cows, deer and goats.

“Monkeys and apes would have been eating fundamentally different things,” said Jablonski. “Apes eat fruits, flowers, things easy to digest, while monkeys eat leaves, seeds and even more mature leaves if they have to. Because of this different digestion, they don’t need to drink free water, getting all their water from vegetation.”

These monkeys do not have to live near bodies of water and can survive periods of dramatic climatic change.

“These monkeys are the same as those found in Greece during the same time period,” said Jablonski. “Suggesting they spread out from a center somewhere in central Europe and they did it fairly quickly. That is impressive when you think of how long it takes for an animal to disperse tens of thousands of kilometers through forest and woodlands.”

While there is evidence that the species began in Eastern Europe and moved out from there, the researchers say the exact patterns are unknown, but they do know the dispersal was rapid, in evolutionary terms. During the end of the Miocene when these monkeys were moving out of Eastern Europe, apes were becoming extinct or nearly so, everywhere except in Africa and parts of Southeast Asia.

“The late Miocene was a period of dramatic environmental change,” said Jablonski. “What we have at this site is a fascinating snapshot of the end of the Miocene — complete with one of the last apes and one of the new order of monkeys. This is an interesting case in primate evolution because it testifies to the value of versatility and adaptability in diverse and changing environments. It shows that once a highly adaptable form sets out, it is successful and can become the ancestral stock of many other species.”

References: Nina G.Jablonski, Denise F.Sug et al., “Mesopithecus pentelicus from Zhaotong, China, the easternmost representative of a widespread Miocene cercopithecoid species”, Journal of Human Evolution
Volume 146, September 2020, 102851, doi: https://doi.org/10.1016/j.jhevol.2020.102851 link: https://www.sciencedirect.com/science/article/pii/S0047248420301123?via%3Dihub

Provided by Penn State