How food availability could catalyze cultural transmission in wild orangutans

The proverb “necessity is the mother of invention” has been used to describe the source from which our cultural evolution springs. After all, need in times of scarcity has forced humans to continually invent new technologies that have led to the remarkable cumulative culture of our species. But an invention only becomes cultural if it is learned and disseminated by many individuals. In other words, the invention must be socially transmitted.

But what are the forces that drive social transmission? A long-term study covering 18 years of data on wild orangutans suggests that the answer may be found in the animal’s environment and the availability of respective resources. The research is published in the journal iScience.

A team from two Max Planck Institutes and the University of Leipzig studied how male orangutans learn from others and found that individuals who grew up in habitats with abundant food had a greater propensity to pay attention to social information. This finding demonstrates how an animal’s ecology can affect its opportunities for social learning, and therefore the likelihood that a new behavior can become an innovation with cultural properties.

“We have shown that the ecological environment of animals and the availability of respective resources have knock-on effects on an individual’s opportunities for social learning, but also on its propensity for social learning over evolutionary time “, explains first author Julia Mörchen.

The team from the Max Planck Institutes for Evolutionary Anthropology (MPI-EVA) and Animal Behavior (MPI-AB) and the University of Leipzig (UL) studied adult male orangutans from wild populations in Borneo and from Sumatra. “Due to their unique life history, adult males offer unique insight into orangutan social learning,” explains Mörchen, a doctoral student at the University of Leipzig.

Once males achieve independence, they leave their native habitat in which they grew up and spend the rest of their lives as nomads roaming the rainforest. “This means that humans are like perpetual tourists, so they must constantly learn crucial behaviors, such as which foods are safe to eat, from experienced locals,” says Mörchen. To learn the necessary new skills, migrant males observe resident orangutans in a behavior known as “scanning.”

Researchers studied orangutans in Borneo and Sumatra, collecting data on instances where migrant males observed locals. In both populations, they found that males spent more time near others and looked at them more when food was more abundant in the environment. The authors say this proves that an animal’s environment can modulate social learning.

“When things are going well, orangutans spend more time in close contact, which provides more opportunities for social learning,” says Mörchen.

The findings deepened when the team compared migrant men from Sumatra and Borneo to see how peering rates differed. Sumatran orangutans live in food-rich habitats, while populations in Borneo live with low and fluctuating food availability. Not surprisingly, men from Sumatran populations spent more time observing than men from Borneo. But this observation persists, even after taking into account the effects of food availability.

“It’s not just that Sumatran males had more food nearby and therefore spent more time observing,” says Mörchen. “We found that Sumatran men had a higher overall propensity to watch than their Bornean counterparts.”

The authors say the study cannot disentangle the mechanisms behind the difference in propensities to engage with social information. “This could be the result of developmental effects on Bornean and Sumatran orangutans growing up in different ecological conditions,” says Mörchen. “Or it could be the result of genetic differences between species that split around 674,000 years ago, or a combination of the two.”

Lead author Caroline Schuppli, from MPI-AB, explains: “Our study provides insight into how ecology can affect cultural transmission. We show that food availability modulates opportunities for social learning and therefore the likelihood that new behaviors become cultural.

Lead author Anja Widdig, from MPI-EVA and UL, adds: “Finding such effects of dominant food availability on social tolerance and observing the less sociable and more distant ape species of humans indicate a deep evolutionary origin of ecological effects. on social learning propensities in the hominid lineage and their potential presence in other lineages.