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A shared understanding

In the field and in the lab, Kobe University Associate Professor Shinya Yamamoto reveals how cooperation has evolved in our closest primate relatives

After flying across the world, sailing down the Congo River for two days, and driving three hours in an SUV, Shinya Yamamoto finally arrived at his research site. It was March of 2016, and Yamamoto had come to the Malebo field station in the Democratic Republic of Congo to study bonobos, a close relative of the chimpanzee.

Back at work at Kobe University in Japan, the 34-year-old comparative psychologist has made a name for himself by demonstrating how captive chimpanzees share tools, helping each other upon request, but typically only after being asked first for assistance (1). And even when chimps are able to understand their requestor’s needs, Yamamoto has shown that these great apes do not help until they are explicitly entreated (2). Thus, Yamamoto’s research has shown, proactivity in human cooperation may be unique in the animal kingdom

In recent years, Yamamoto has branched out into what he calls “a two-by-two research paradigm,” involving both lab experiments and fieldwork with two of our closest living ape cousins: chimpanzees and bonobos. “In captivity, I can investigate in detail how their intelligence works, and, in the wild, I can examine this cognition in a natural setup,” Yamamoto says. “It’s very complementary.”

Bonobo generosity

In 2015, Yamamoto published the results of a major study of wild bonobos. Over four field seasons in the Wamba forest — some 800 kilometers northeast of his newer field site in Malebo — Yamamoto tracked the Congolese apes, watching to see how they shared a kind of tropical fruit known as junglesop. Each day, he would wake at 4am to try to find sleeping bonobos, before they started traveling around the forest foraging for food. He would follow them for the rest of the day, recording behaviors in a notebook or on video.

After 10 months of observing the bonobos, Yamamoto documented 150 instances of fruit sharing, mostly between adult females. And unlike chimpanzees, who will only part with meat when harassed by beggars or when the exchange is reciprocated, the bonobos tolerated others taking a cut and shared the abundant junglesop fruit peacefully (3).

Now Yamamoto plans to repeat the study in the forest-savanna mosaic ecosystem of Malebo, where fruit is less abundant. He wants to see if the bonobos’ inclination to share is affected by the scarcity of resources. Yamamoto is also running ongoing studies with chimpanzees at a field site in Bossou, Guinea, where he’s investigating similarities and differences in cooperation between the two sister species.

Social intelligence

Colleagues describe Yamamoto as a skilled experimentalist with an eye for innovative study designs and a knack for comparative approaches in non-human animals. “Shinya is a very thorough and rigorous scientist, fair in the interpretation of his results and keen to explore and challenge concepts that are thought to define human uniqueness,” says Tatyana Humle, a primatologist from the University in Kent, UK, who collaborates with Yamamoto at the Kyoto University Primate Research Institute. “I have no doubt that Shinya will continue to produce exciting and groundbreaking research.”

While Yamamoto continues to work with wild apes in Africa and with captive ones in collaboration with Kyoto University, he has also begun a project in Kobe to probe the social intelligence of horses and dogs. His goal is to see how interactions with humans affect how these domestic animals behave in group situations.

Ultimately, whether studying horses and dogs or chimpanzees and bonobos, a single-minded mission drives Yamamoto’s explorations: “I want to understand how sociality has evolved,” he says. And by studying these animals, Yamamoto hopes to unravel some hidden truths about the origins of human cognition.

“Chimpanzees and bonobos are the closest relatives with humans,” Yamamoto says. “So when we understand them, we can understand ourselves.”

Left
Wild bonobo eating junglesop in the Wamba forest, Democratic Republic of Congo.
Credit: © 2015 Shinya Yamamoto, Kobe University

Right
Chimpanzees transfer tools upon their partners’ request.
Credit: Reproduced from Ref. 1 and licensed under CC BY 4.0 © 2009 S. Yamamoto et al.
(http://creativecommons.org/licenses/by/4.0/legalcode)

References:

Associate Professor YAMAMOTO Shinya (Graduate School of Intercultural Studies)
  1. Yamamoto, S., Humle, T. & Tanaka, M. Chimpanzees help each other upon request. PLoS ONE 4, e7416 (2009). http://dx.doi.org/10.1371/journal.pone.0007416
  2. Yamamoto, S., Humle, T. &Tanaka, M. Chimpanzees’ flexible targeted helping based on an understanding of conspecifics’ goals. Proceedings of the National Academy of Sciences USA 109, 3588–3592 (2012). http://dx.doi.org/10.1073/pnas.1108517109
  3. Yamamoto, S. Non-reciprocal but peaceful fruit sharing in wild bonobos in Wamba. Behaviour 152, 335–357 (2015). http://dx.doi.org/10.1163/1568539X-00003257