Monkeys join hands while grooming each other – and each group has a clear grip

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Chimpanzees interlock while grooming each other, and each group has its own specific grip, which researchers say is comparable to a ‘secret handshake’ in humans.

The monkeys are known to be a cultural species, and the new study by scientists at the University of Antwerp focused on hand grips in two different groups for 12 years.

This is a peculiar social custom among chimpanzee species related to grooming, but found only in a relatively small number of chimpanzee populations.

The team looked at different styles of hand closure between the two groups and found that ‘group belonging to the group’ is the reliability identified based on the style of hand closure used.

This shows that chimpanzees can adopt and stick to group-specific cultural practices for extended periods of time, despite significant changes in the population over time.

The study’s authors also found that male chimpanzees “grabbed wrists,” suggesting they were trying to assert control or dominance over their partner.

Chimpanzees interlock while grooming each other, and each group has its own distinct grip, which researchers say is comparable to a 'secret handshake' in humans

Chimpanzees interlock while grooming each other, and each group has its own distinct grip, which researchers say is comparable to a ‘secret handshake’ in humans

ANIMAL CULTURE: SPREAD THROUGH LEARNING

There is growing evidence that animals, and not just humans, have forms of culture.

This is learned through socially transmitted behaviors and is a theory that dates back to classical times.

Andrew Whiten says cultural behavior includes distinctive socially learned behaviors, including rock handling, potato washing, and other patterns.

In an example of animal culture, a group of chimpanzees studied in a wildlife sanctuary in Zambia was found to develop a cultural tradition of fashionably wearing a blade of grass in one ear.

A chimpanzee named Julie started the trend before others copied it, with a majority of the group (eight out of twelve) following suit.

Culture is a hallmark of the human species, both in terms of sharing information about new inventions, such as instruments, and adhering to social conventions.

Although material culture, such as the use of educational resources, has been reported across the animal kingdom, there is little evidence of social culture in animals.

In addition, there is a lack of evidence showing cultural stability in animals that spread over generations and persist within specific groups.

The team behind this study used a large 12-year data set to investigate chimpanzees’ social interactions and behavior within two different groups.

They found that the chimpanzees “adhere to arbitrary group-specific preferences for hand grips” that cannot be explained by genetics or the environment they are in.

This discovery was true “despite substantial changes in group composition over the study period,” the study authors said.

All chimpanzees also had different behaviors within their repertoire that were unique in themselves and independent of the handshake process.

Despite all this, chimpanzees still maintained consistencies of behavior within the group and between groups similar to the “cultural phenomenon in humans.”

“These findings indicate that human culture, including its arbitrary social conventions and long-term stability, is rooted in our evolutionary history.”

The monkeys are known to be a cultural species, and the new study from scientists at the University of Antwerp focused on hand grips in two different groups for 12 years.

The monkeys are known to be a cultural species, and the new study from scientists at the University of Antwerp focused on hand grips in two different groups for 12 years.

To call a behavior “ cultural, ” scientists generally assess on three criteria: emergence through social learning, how it is shared among group members, and how long it lingers within the group, or its lifespan.

There have been a number of studies demonstrating social behavior in animals, but very few have done this over a long period of time to demonstrate stability and longevity.

One of the few established tool uses in wild chimpanzees over a 25-year period, showing that materials used remained consistent over time, despite large numbers of females leaving the group.

This is a peculiar social custom among chimpanzee species related to grooming, but found only in a relatively small number of chimpanzee populations.

This is a peculiar social custom among chimpanzee species that is related to grooming, but is only found in a relatively small number of chimpanzee populations.

CHIMPANZEE (PAN TROGLODYTES)

The chimpanzee is a species of great apes found in the forest and savannah of tropical Africa.

They are closely related to the Bonobo and evidence of DNA sequencing and fossils show that Pan, of which chimpanzees are members, is a sister of the human lineage.

This suggests that humans are chimpanzees’ most living relatives.

They are endangered on the IUCN Red List, affecting between 170,000 and 300,000 individuals in the world.

They grow to about four feet long and about 100 pounds, with babies about eight months pregnant.

They live in groups of up to 150, but travel and forage in groups during the day.

They are part of a male-dominated society and have been shown to use tools by modifying sticks, rocks, grass and leaves to hunt and forage.

That study was a focus on material culture, but the authors of this new study said few have explored long-term social culture.

The new study looked at a range of material and sociocultural activities in two groups of chimpanzees over 12 years, excluding activities related to adaptive value – social foraging and personal interactions.

They found a supportive social activity that changed according to the group, but remained the same among members of the same group: hand clip care.

That is the process of two chimpanzees holding and shaking hands at the end of or during a grooming session, with marked variations in the way they are performed in groups.

In addition to differences between groups, the team also found differences between male and female chimpanzees grabbing hands.

They found females engaged in palm gripping, while males engaged in wrist gripping, which they say may be the males attempting to assert dominance.

The wrist position of the subject allows the partner to bear the weight of the subject’s arm, which can be considered by the partner as a prosocial act.

“While plausible, more research is needed to investigate this conjecture, including how such configurations are initiated,” the authors wrote.

Finding a stable culture, even with handshakes, in chimpanzees shows that the social culture in the animals is robust and persistent, the team said.

The study's authors also found that male chimpanzees

The study’s authors also found that male chimpanzees “grabbed wrists,” suggesting they were trying to assert control or dominance over their partner.

It shows that ‘animals can develop and maintain cultural preferences in the field of random, non-fitness related phenomena, just like the human species.

“And animal cultures may possess the necessary ingredients in terms of adherence and longevity to be a powerful force in the co-evolutionary dynamics of gene culture, shaping phenotypes as well as genotypes in animals.”

The findings are published in the journal Biology Letters.

WHAT IS CONVERGENT EVOLUTION?

Convergent evolution is the process by which two unrelated species independently develop similar traits to adapt to similar problems or habitats.

Contemporary examples of convergent evolution are the hedgehog and the tenrec – a Madagascan animal that closely resembles the hedgehog but is completely unrelated.

An example of convergent evolution is the similar flight / wing nature of insects, birds, pterosaurs and bats.

All four have the same function and are similar in structure, but each has evolved independently.

The tenrec is a Madagascan animal very similar to the hedgehog.  It has developed spines all over its body and similar foraging techniques to survive in the same ecological niche that the hedgehog occupies in the UK.

Common in the UK, the hedgehogs are nocturnal animals and have a wide variety of food sources

The tenrec (left) and the hedgehog (right) are the perfect example of convergent evolution. One is commonly found in British gardens and the other is exclusive to the island of Madagascar. They are not related

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