Environmental variability supports chimpanzee behavioural diversity

Abstract

Large brains and behavioural innovation are positively correlated, species-specific traits, associated with the behavioural flexibility animals need for adapting to seasonal and unpredictable habitats. Similar ecological challenges would have been important drivers throughout human evolution. However, studies examining the influence of environmental variability on within-species behavioural diversity are lacking despite the critical assumption that population diversification precedes genetic divergence and speciation. Here, using a dataset of 144 wild chimpanzee (Pan troglodytes) communities, we show that chimpanzees exhibit greater behavioural diversity in environments with more variability — in both recent and historical timescales. Notably, distance from Pleistocene forest refugia is associated with the presence of a larger number of behavioural traits, including both tool and non-tool use behaviours. Since more than half of the behaviours investigated are also likely to be cultural, we suggest that environmental variability was a critical evolutionary force promoting the behavioural, as well as cultural diversification of great apes.

Did Human Culture Emerge in a Cultural Evolutionary Transition in Individuality?

“…Some degree of group-level informational uniqueness may thereby be theoretically expected in an early hominin Pan-like state. There is also some support for this in field studies where substantial between-group variation in traditions has been found between chimpanzee communities (e.g., Whiten et al 1999Whiten et al , 2001Sanz and Morgan 2007;Schöning et al 2008;Lycett et al 2009;Boesch 2012;Koops et al 2015;van de Waal 2018;Kaufhold and Van Leeuwen 2019;Kalan et al 2020).…”

Recent genetic connectivity and clinal variation in chimpanzees

“…Since our results have demonstrated that recent genetic variation in chimpanzees contains little geographic structure on a broad scale, behavioural flexibility may also play an important evolutionary role in their adaptability to environmental heterogeneity 63 . Chimpanzees have diverse and variable behavioural repertoires 64,65 that often vary among nearby communities 66 , they utilize learned techniques to harvest otherwise unobtainable foods 67 and their bevavioural diversity increases with environmental variability 68 . Indeed, chimpanzees living in arid habitats employ specialized behaviours to regulate the thermal exposure 8 and spontaneously innovate novel behaviours in response to increased environmental complexity arising from anthropogenic pressures [69][70][71] .…”

Environmental Factors Are Stronger Predictors of Primate Species’ Distributions Than Basic Biological Traits

“…food sources and many vary their diets significantly according to resource availability (e.g., Cercopithecus mitis: Coleman and Hill 2015). Many genera, including Cercopithecus and Pan, also alter their time budgets, activity levels, group size, and home range in different locations (Campera et al 2014;Fan et al 2013;Kalan et al 2020;Korstjens et al 2018;Zhou et al 2013). As these biological traits are not necessarily fixed in primates, the relationship between diet and environmental factors may be less clear than in other taxa in which biological trait filtering has been shown to be important, such as birds and butterflies (Hanspach et al 2015;Wittmann et al 2016).…”