New tool use has arisen among wild chimpanzees, and primatologists are getting to watch its spread through a chimp community. Initially, apes learned from their peers, but now the techniques are being passed by mothers to children. The transmission patterns may resemble the ways the first humans learned to copy early geniuses' innovations.
“Leaf-sponging”, where leaves are used to collect water, is seen among all chimpanzee populations, albeit with local variations. In 2011, Sonso chimpanzees in Uganda's Budongo Forest started using moss instead, something that had previously been witnessed in only one chimp population and apparently new to Sonsos. The moss improved the collection of nutritious minerals suspended in water in a clay pit.
A 2014 study reported on how eight other chimpanzees came to use the technique, seven by watching others, while one used a sponge another chimp had discarded.
A paper in Science Advances updates this work, showing that moss-sponging is now well established among the Sonso community and is being passed on by some mothers to their children.
Three years after moss-sponging appeared, Swiss researchers including University of Neuchâtel PhD student Noemie Lamon presented Sonso chimpanzees with a choice of naturally available leaves and moss. Among 40 visitors to the pit, 55 percent were seen using moss sponges, although half of them also used leaves on occasion.
Investigating the familial relations of the troop members, the team found the moss-spongers were predominantly offspring of those chimpanzees who adopted the practice in the first rush after its invention.
Although it's impossible to be certain, a team studying the Budongo chimps believe they witnessed the moment when moss-sponging was invented, as a 29-year-old male called Nick manufactured a sponge and used it to get water from the pit. To be on the ground floor of seeing how an animal innovation spreads in the wild is an almost unprecedented opportunity.
An adult female, Namibi, was watching Nick as he used the sponge, and copied the idea immediately. Seven others followed suit within six days, but after that the spread seems to have slowed, perhaps because it is hard to teach most old chimps new tricks.
However, the initial group of moss-sponge early adopters were sufficient to establish a sub-culture, which is now being passed on to later generations. Although they admit it is possible certain families are genetically more suited to adopting new technologies, the authors consider this unlikely, and transmission is probably occurring through mothers teaching their children.
The pattern of transmission, first to peers and then to offspring, matches that seen among Japanese macaques after one individual started playing with stones, suggesting the pattern may be a common one for primates, and one used by early humans.
Image credit above: A chimpanzee mother squashes a parasite on a leaf as her son imitates her. Mother to child learning appears to be the main way new technologies spread among chimps. Thibaud Gruber
The clay pit between the roots of a tree where moss-sponging was invented. The water is rich in minerals that chimpanzees need, but the location makes access a challenge without using sponging. Lamon et al./Science Advances