How Culture Shapes Human Evolution
ST. ANDREWS – Is there an evolutionary explanation for humanity’s greatest successes – technology, science, and the arts – with roots that can be traced back to animal behavior? I first asked this question 30 years ago, and have been working to answer it ever since.
Plenty of animals use tools, emit signals, imitate one another, and possess memories of past events. Some even develop learned traditions that entail consuming particular foods or singing a particular kind of song – acts that, to some extent, resemble human culture.
But human mental ability stands far apart. We live in complex societies organized around linguistically coded rules, morals, and social institutions, with a massive reliance on technology. We have devised machines that fly, microchips, and vaccines. We have written stories, songs, and sonnets. We have danced in Swan Lake.
Developmental psychologists have established that when it comes to dealing with the physical world (for example, spatial memory and tool use), human toddlers’ cognitive skills are already comparable to those of adult chimpanzees and orangutans. In terms of social cognition (such as imitating others or understanding intentions), toddlers’ minds are far more sophisticated.
The same gap is observed in both communication and cooperation. Vaunted claims that apes produce language do not stand up to scrutiny: animals can learn the meanings of signs and string together simple word combinations, but they cannot master syntax. And experiments show that apes cooperate far less readily than humans.
Thanks to advances in comparative cognition, scientists are now confident that other animals do not possess hidden reasoning powers and cognitive complexity, and that the gap between human and animal intelligence is genuine. So how could something as extraordinary and unique as the human mind evolve?
A major interdisciplinary effort has recently solved this long-standing evolutionary puzzle. The answer is surprising. It turns out that our species’ most extraordinary characteristics – our intelligence, language, cooperation, and technology – did not evolve as adaptive responses to external conditions. Rather, humans are creatures of their own making, with minds that were built not just for culture, but by culture. In other words, culture transformed the evolutionary process.
Key insights came from studies on animal behavior, which showed that, although social learning (copying) is widespread in nature, animals are highly selective about what and whom they copy. Copying confers an evolutionary advantage only when it is accurate and efficient. Natural selection should, therefore, favor structures and capabilities in the brain that enhance the accuracy and efficiency of social learning.
Consistent with this prediction, research reveals strong associations between behavioral complexity and brain size. Big-brained primates invent new behaviors, copy the innovations of others, and use tools more than small-brained primates do. Selection for high intelligence almost certainly derives from multiple sources, but recent studies imply that selection for the intelligence to cope with complex social environments in monkeys and apes was followed by more restricted selection for cultural intelligence in the great apes, capuchins, and macaques.
Why, then, haven’t gorillas invented Facebook, or Capuchins built spacecraft? To achieve such high levels of cognitive functioning requires not just cultural intelligence, but also cumulative culture, in which modifications accumulate over time. That demands transmission of information with a degree of accuracy of which only humans are capable. Indeed, small increases in the accuracy of social transmission lead to big increases in the diversity and longevity of culture, as well as to fads, fashions, and conformity.
Our ancestors were able to achieve such high-fidelity information transmission not just because of language, but also because of teaching – a practice that is rare in nature, but universal among humans (once the subtle forms it takes are recognized). Mathematical analyses reveal that, while it is generally difficult for teaching to evolve, cumulative culture promotes teaching. This implies that teaching and cumulative culture co-evolved, producing a species that taught relatives across a broad range of circumstances.
It is in this context that language appeared. Evidence suggests that language originally evolved to reduce the costs, increase the accuracy, and expand the domains of teaching. That explanation accounts for many properties of language, including its uniqueness, power of generalization, and the fact that it is learned.
All of the elements that have underpinned the development of human cognitive abilities – encephalization (the evolutionary increase in the size of the brain), tool use, teaching, and language – have one key characteristic in common: the conditions that favored their evolution were created by cultural activities, through selective feedback. As theoretical, anthropological, and genetic studies all attest, a co-evolutionary dynamic – in which socially transmitted skills guided the natural selection that shaped human anatomy and cognition – has underpinned our evolution for at least 2.5 million years.
Our potent capacity for imitation, teaching, and language also encouraged unprecedented levels of cooperation among individuals, creating conditions that not only promoted longstanding cooperative mechanisms such as reciprocity and mutualism but also generated new mechanisms. In the process, gene-culture co-evolution created a psychology – a motivation to teach, speak, imitate, emulate, and connect – that is entirely different from that of other animals.
Evolutionary analysis has shed light on the rise of the arts, too. Recent studies of the development of dance, for example, explain how humans move in time to music, synchronize their actions with others, and learn long sequences of movements.
Human culture sets us apart from the rest of the animal kingdom. Grasping its scientific basis enriches our understanding of our history – and why we became the species we are.