Which Evolves Faster, Culture or Biology?
(Inside Science) -- Modern human culture seems to evolve at a dizzying rate. Changes in the media we consume and technology we use often far outstrip our ability to keep up. But there have been few attempts to actually measure this phenomenon.
“All we have is this sense that culture evolves really quickly, but relative to what?” said Armand Leroi, an evolutionary biologist at Imperial College London.
Leroi and his colleagues believe that cultural traits evolve much like biological ones, in that they are formed via descent by modification. “When making something new, people start with something that someone else has done,” he said.
So they used the tools of evolutionary biology to measure how fast selections of human cultural objects are evolving, and compared them to the rate of evolution of a variety of animal populations.
They looked at four modern cultural objects -- pop songs on the Billboard Hot 100 between 1960 and 2010; American, Irish and English novels published between 1840 and 1890; scientific articles published in the British Medical Journal between 1960 and 2008; and car models sold in the U.S. between 1950 and 2010 -- and measured how fast various traits changed over time. In their paper, published today in the journal Nature Human Behaviour, They reviewed changes in the topics of the novels and scientific articles, body size of the cars, and musical content of the songs.
They compared these rates with the rate of evolution of a dozen animals, including some famous examples such as Darwin’s finches from the Galapagos Islands and pepper moths in northern England, and found something surprising. The cultural objects didn’t evolve very quickly -- in fact they changed around the same speed as most of the animals in the study.
“The songs may change, but the music stays the same,” said Leroi.
Though there might be a great deal of variation over the short term, over longer time scales trends revert back to a more conservative mean -- and that mean shifts quite slowly. Despite rapid developments in medical treatments, for example, the general medical topics of 50 years ago are often the same ones that appear in today’s medical journals.
Leroi thinks this could be due to a psychological phenomenon in which people continually prefer an intermediate level of novelty, so the baseline shifts slowly over time. Think of how the curvy and rounded pickup trucks of the 1940s slowly evolved into the more boxy ones of today, but the sudden jump to Tesla’s angular Cybertruck seems like a bit too much, too fast.
The study does have one major drawback, Leroi admits. Because they were limited to what datasets they were able to get, the researchers were unable to analyze modern gadgets like computers or cellphones. And those are the things that most people would probably highlight when thinking about cultural evolution today. Leroi expects that including them would probably change the results.
“If we were able to look at computers, we would almost certainly find that they are evolving very fast compared with organic traits,” he said.
But Charles Perreault, an anthropologist at Arizona State University in Tempe, thinks Leroi’s team is asking the wrong question. The animals they made the comparison with all have very short generation times, on the order of about one year.
“The biologically relevant question to ask when comparing rates of cultural and biological evolution is ‘how much faster is cultural evolution compared to the expected pace of biological evolution for a species with a generation time like ours’,” said Perreault. “If moths and snails lived as long as humans do, how fast would they evolve?”
Perreault has done a similar study, comparing the rate of evolution of multiple ancient artifacts such as arrowheads and pottery shards with biological evolution, and found that they changed much more rapidly than biological traits on human time scales. And the fact that Leroi found that cultural traits evolve at a similar rate to fast-living organisms shows the same thing, he said.
Leroi agrees that even the slowest-changing objects evolve faster than human biology, but said comparing cultural traits to organisms with shorter lifespans makes sense. If you think of the “offspring” of a pop song as other songs inspired by it, then a roughly one-year “generation time” -- to allow for the writing, production and release of new music -- seems like a reasonable estimate, on average.
In any case, Leroi said the speed of cultural evolution is not the most important claim he is making. Rather, he hopes to demonstrate the potential to use tools from evolutionary biology in the study of culture to measure how it is changing and what kinds of forces are shaping those changes.
“Human culture can be a science, and it should be an evolutionary science,” he said. “It can be a science that looks a lot like evolutionary biology.”