When it comes to learning complex skills, chimpanzees may not be so different from humans — at least when it comes to mastering advanced tool use. A study published in PLOS Biology has revealed that wild chimpanzees can take up to 15 years to fully develop the motor and cognitive skills needed to efficiently use sticks as tools for foraging.
The research, led by scientists from the Max Planck Institute for Evolutionary Anthropology and the French National Center for Scientific Research, sheds new light on the protracted development of tool use in our closest living relatives. The findings suggest that, like humans, chimpanzees require an extended period of learning and practice to become proficient in complex tasks.
To investigate the ontogeny of tool use in chimpanzees, researchers observed 70 wild chimps ranging from infants to adults in the Taï National Park, Côte d’Ivoire. Over the course of seven-and-a-half years, they analyzed 1,460 stick use events, focusing on how the chimpanzees manipulated sticks to extract hard-to-reach, nutrient-rich foods like honey, ants, and larvae.
Researchers identified several distinct hand grips employed by the chimpanzees, each involving a different number of digits and varying degrees of precision. The “full hand grip,” which uses four flexed digits with no independent thumb, was favored by the youngest chimps. As they matured, the chimpanzees increasingly utilized more advanced grips, such as the “full hand thumb grip” (involving an opposable thumb) and the “digits grip” (employing two or three independent fingers).
While the digits grip became the predominant technique by age 6, it didn’t become ubiquitous until age 15 — long after chimpanzees are weaned from their mothers. This prolonged development suggests that mastering advanced tool use involves more than just physical maturation; it also requires cognitive development and extensive practice.
Researchers also found that adult chimpanzees were better at matching their hand grip to the specific task at hand. For example, they favored power grips for pounding actions and precision grips for more delicate maneuvers. Younger chimps, in contrast, were less adept at this behavioral flexibility, indicating that task understanding improves with age and experience.
The study even revealed that learning to use the appropriate tool actions for extracting hidden foods, such as larvae, took significantly longer than for visible foods like nut kernels. While chimpanzees mastered the efficient “levering” technique for nuts by age 5, they didn’t consistently apply this method to larvae extraction until their teenage years. This suggests that more cognitively demanding tasks, where the problem and solution are less readily apparent, require even more extensive learning.
“In wild chimpanzees, the intricacies of tool use learning continue into adulthood. This pattern supports ideas that large brains across hominids allow continued learning through the first two decades of life,” the study authors say in a media release.
Researchers propose that this protracted skill development may be facilitated by chimpanzees’ prolonged association with their mothers, which can last until age 12. This extended period of parental care and social learning likely plays a crucial role in the acquisition of complex foraging techniques.
These findings have important implications for our understanding of human evolution. The extended juvenile dependency and prolonged learning observed in chimpanzees may offer insights into the origins of the even more pronounced delays in human development. Some researchers have suggested that the rapid brain expansion and extended learning capacities seen in the hominin lineage may have been selected for by the demands of complex foraging and tool use.
