Wild chimpanzees appear to learn skills from each other and then – much like humans do – improve these techniques from one generation to the next.

In particular, young women who migrate between groups bring their cultural knowledge with them, and groups can combine new techniques with existing ones to become better at foraging. Such “cumulative culture” means that some chimpanzee societies become more technologically advanced over time — albeit very slowly, says Andrew White at the University of St Andrews, UK.

“If chimpanzees have some cultural knowledge that the society they move to doesn’t have, they can pass it on – just like they pass genes on,” he says. “And then that culture builds from there.”

Scientists already knew that chimpanzees were capable of using tools in sophisticated ways and passing that knowledge on to their offspring. But compared to the rapid technological development of humans, it seemed that chimpanzees were not improving on previous innovations, says Whiten. The fact that chimpanzee tools are often made from biodegradable plants makes it difficult for researchers to trace their cultural evolution.

Cassandra Gunasekaram at the University of Zurich in Switzerland suspected she might be able to apply genetic analysis to the puzzle. While male chimpanzees stay in their home range, young females leave their home ranges to find mates elsewhere. She wondered if these women have brought their skills with them to their new groups.

To find out, she and her colleagues obtained data on 240 chimpanzees representing all four subspecies, which were previously collected by other research groups at 35 study sites in Africa. The data included precise information about which tools, if any, each of the animals used and their genetic connections over the past 15,000 years. “Genetics gives us a kind of time machine for how culture has been transmitted to chimpanzees in the past,” says Whiten. “It’s a revelation that we can get these new insights.”

Some chimpanzees used complex combinations of tools, such as a drill stick and a fishing brush created by pulling a plant stem between their teeth, to hunt termites. The researchers found that the chimpanzees with the most advanced tool sets were three to five times more likely to share the same DNA than those who used simple tools or no tools at all, even though they may live thousands of kilometers away. And advanced tool use was also more strongly associated with female migration compared to simple or no tool use.

“Our interpretation is that these complex tool sets were indeed invented by perhaps building on a simpler form from earlier, and so they must have depended on the transmission of women from the societies that originally invented them to all the other societies along the way,” says Bleka .

“It shows that complex tools would rely on social exchanges between groups – which is very surprising and exciting,” says Gunasekaram.

Thibaud Gruber at the University of Geneva is not surprised by the results, but says the definition of complex behavior is debatable. “Having worked with chimpanzees for 20 years, I would argue that stick use is inherently complex,” he says.

For example, his own team found what they called cumulative culture in chimpanzees that make mushrooms out of moss instead of leaves—which isn’t more complicated, but works more effectively to soak up mineral-rich water from mud pits. – It is not a question of being more complex, but of just having a technology that is based on a previously established one, he says.

Cumulative culture is still markedly slower in chimpanzees compared to humans, probably because of their different cognitive abilities and lack of speech, Gunasekaram says. Additionally, chimpanzees interact much less with others outside their communities compared to humans, giving them fewer opportunities to share culture.