Kibale Chimpanzee Project

Older chimpanzees accentuate the positive

A new KCP study published in Science shows that wild chimpanzees share social aging patterns with humans, by prioritizing strong social bonds and interacting with others in increasingly positive ways as they get older. 

KCP researchers led by Dr. Alex Rosati and Dr. Zarin Machanda leveraged our exceptional long-term dataset to test socioemotional selectivity theory – an influential idea in psychology aimed at explaining why humans show changes in social interactions during aging. Socioemotional selectivity theory proposes that people shift their social behavior from a focus on forming new friends in young adulthood, to maintaining a smaller network of close, fulfilling relationships in old age. The proposal is that this shift happens because of our human ability to monitor our own personal time horizons—how much time we have left in our life—which causes us to prioritize emotionally-fulfilling relationships when time is perceived to be running out.

Using 20 years of behavioral data, researchers found that chimpanzees, like humans, increasingly prioritized mutual and equitable friendships with others that invested in them as they got older. Younger adults, in contrast, were more likely to form lopsided relationships where their partner did not reciprocate. Older chimpanzees also were more likely to be seen alone, but tended to socialize more with important partners when they did join the group. Finally, they showed a positivity bias in their overall behavior: reducing their aggressive behavior while maintaining levels of affiliative grooming. 

Taken together, these results show that chimpanzees share these special social aging patterns with humans, even though they do not have the same rich future time perspective and knowledge of their own mortality that we have. This is the first demonstration that a nonhuman shares these characteristics with us. The shared pattern between chimpanzees and humans could represent an adaptive response where older adults focus on important social relationships that provide benefits, and avoid interactions that have negative consequences as they lose competitive fighting ability. This research highlights how long-term behavioral datasets from wild animals like chimpanzees can help us understand and promote healthy aging in humans. 

A look at the Kibale Snare Removal Project

Detailed coverage of KCP’s snare removal program from Mongabay.

Jess Hartel interviewed for ASP

KCP’s Dr. Jessica Hartel discusses the Kibale Snare Removal Program, which protects chimpanzees in Uganda while engaging with local communities in conservation and education. Interview for Welfare “Hot Topics” – the American Society of Primatologists:

Richard Wrangham on human self-domestication in the Wall Street Journal

We differ from our ancient ancestors in ways similar to how dogs differ from wolves. Download the pdf file here:

Humans: The Domesticated Primate (pdf)



Get your KCP t-shirt for World Chimpanzee Day

July 14, 2018 is World Chimpanzee Day! In anticipation of this exciting occasion, we are offering the first Kibale Chimpanzee Project t-shirts, featuring our fabulous, color logo by artist Eric Losh. For every donation of $30 (US) that we receive by the end of June, we will send you one super-soft, heather gray t-shirt for World Chimpanzee Day. (Donors outside the US, please include an additional $5 for shipping.)

Donations can be made through the Paypal link on our website: Under “Special Instructions” please enter your shipping address, and indicate the style (men’s or women’s) and size (S-XXL) that you prefer. Shirts will be shipped in early July.

Your donation will support KCP’s conservation and education efforts in Kibale National Park and the surrounding communities, including scholarships for local children to attend secondary school.

New book from Harvard University Press.

Now available from Harvard University Press! Chimpanzees and Human Evolution systematically compares us with our closest living relatives, attempting to account for the evolution of both similarities and differences. Contributors include current and former KCP researchers – Richard Wrangham, Martin Muller, Melissa Emery Thompson, Katie Slocombe, Sherry Nelson, Herman Pontzer, Ian Gilby, Brian Hare, and Michael Wilson. From the Press:

“Knowledge of chimpanzees in the wild has expanded dramatically in recent years. This comprehensive volume, edited by Martin Muller, Richard Wrangham, and David Pilbeam, brings together scientists who are leading a revolution to discover and explain what is unique about humans, by studying their closest living relatives. Their observations and conclusions have the potential to transform our understanding of human evolution.

Chimpanzees offer scientists an unmatched view of what distinguishes humanity from its apelike ancestors. Based on evidence from the hominin fossil record and extensive morphological, developmental, and genetic data, Chimpanzees and Human Evolution makes the case that the last common ancestor of chimpanzees and humans was chimpanzee-like. It most likely lived in African rainforests around eight million years ago, eating fruit and walking on its knuckles. Readers will learn why chimpanzees are a better model for the last common ancestor than bonobos, gorillas, or orangutans. A thorough chapter-by-chapter analysis reveals which key traits we share with chimpanzees and which appear to be distinctive to Homo sapiens, and shows how understanding chimpanzees helps us account for the evolution of human uniqueness. Traits surveyed include social behaviors and structures, mating systems, diet, hunting practices, tool use, culture, cognition, and communication.

Edited by three of primatology’s most renowned experts, with contributions from 32 scholars drawing on decades of field research, Chimpanzees and Human Evolution provides readers with detailed up-to-date information on what we can infer about our chimpanzee-like ancestors and points the way forward for the next generation of discoveries.”

Comprehensive, judicious, authoritative, up-to-date, well written, and thoroughly fascinating to anyone interested in either species.—Steven Pinker, author of The Better Angels of Our Nature