Oldowan helicopters dating back to 1.7 million years ago, from Melka Kunture, Ethiopia.
It is well known that human genetics can influence culture, but the idea that culture can also influence genetics is gaining ground. The theory of gene culture coevolution suggests that “the cultural practices we adopt alter the costs and benefits of having certain genes,” explained Catharine Cross, a researcher at the University of St Andrews. “A gene that is advantageous under one cultural practice is not necessarily advantageous under another.”
For example, yam cultivation in West Africa led to deforestation and an increase in standing water, creating a breeding ground for mosquitoes and malaria. This meant that yam farmers with a certain genetic resistance to malaria were more likely to survive than farmers susceptible to malaria. Yam farmers in the region are more likely to have this genetic trait than nearby groups — even speakers of the same language — who grow other crops.
A recent study published in Nature communication has suggested that stone tool-making practices among the ancestors of modern humans may have put evolutionary pressure on individuals who were not very good at communicating, helping to select the genes that would become involved in language. The study found that the use of verbal teaching, compared to learning by imitation, significantly improved the quality and speed of stone tool production. This suggests that individuals with gesture or verbal communication skills could have learned to make tools faster and better, giving them an advantage over individuals who could only imitate.
Play phone call with stone tools
The researchers tested the performance difference using ‘transmission chains’, a method similar to the children’s game on the telephone. The person who starts a chain passes information to the next person, who then passes that information all the way down the chain. This can provide insight into how information changes as it is passed down through generations of people.
In this case, the information passed down the chain was the technique of making Oldowan stone tools. These were the first stone tools to appear in the fossil record about 2.5 million years ago, and were the predominant technology for about 700,000 years until more advanced Acheulean stone tools began to appear.
The first person in each chain was an experimenter skilled in the Oldowan method of hammering sharp flakes of flint off a central core. This person can pass information along the transmission chain in five ways. In the first method, pure imitation, the teacher simply made the tools while the first participant watched, without interaction. Three of the five transmission methods involved some form of interaction: primary education, which allowed the teacher to slow down their movements or shape the participant’s grasp; sign education, to which gestures have been added; or verbal education, which allowed normal speech. Finally, in the fifth method, the participant did not allow any contact with the teacher at all – rather, they had to figure out how to make the tools just by looking at examples created by the teacher.
After a short learning period, the participant had to pass on his new skills to the next participant in the chain via the same transfer method. Participants were paid more if they and their students produced more, higher quality tools, so there was a strong motivation to learn and teach well. Each learning condition had six chains of transmission, with a total of 184 participants.
The results indicated that learning through teaching, rather than reverse engineering or imitation, had a marked impact on outcomes. Participants who experienced active instruction from their teachers produced more better quality flakes at a higher rate, with fewer errors. Unsurprisingly, oral instruction produced the best results, followed by sign instruction, and then elementary education.
Press to communicate
The results are important, the researchers write, because they help us understand the language that might have played in human ancestors during the period when Oldowan tools were in use. It is unlikely that Oldowan tools would have remained unchanged for 700,000 years if the language had emerged at all, they write. This suggests that imitation, which does not transmit information as efficiently, has contributed to sustaining this long period of stagnation. However, it also appears that individuals with better communication skills may have had greater success in tool making, adding to the push that led to the evolution of language and more advanced Acheulean tools.
“This is a rigorously conducted study and a nice improvement on previous studies,” said Dr Alex Mesoudi, who studies cultural evolution at Durham University, and was not involved in the study. “There are very few experiments with real stone tools; many use computer simulations or some even use polystyrene blocks. The use of real stone is a step forward.”
There are certain limitations, he notes, especially the very short time participants have to learn the process — in reality, these techniques would have taken years to master. However, the research shows a benefit of teaching if you have the same amount of time for all different learning methods, he adds.
It’s important not to extrapolate too much from these results, says Cross, one of the paper’s authors. “We’re not saying that what definitely happened is that tools came first and then language caused it. Rather, we think that the ability to use tools and the ability to use language evolved together, and that we can see a benefit of verbal teaching over a limited period of time.”
A possible future avenue for research is cross-cultural exploration, Mesoudi suggests. His own recent work has shown that Chinese participants imitate more than British participants, suggesting that imitation may not be the same everywhere. This could mean that imitation-based learning could be more successful in other cultures, he suggests.
Nature communication2015. DOI: 10.1038/ncomms7029 (About DOIs).