Eat or be eaten. The only reason a creature exists today is because it was strong enough to survive the trials of history — and that includes humans. But according to the New York Times, it’s not just natural selection that is shaping human evolution. Research shows that culture has a powerful impact on our genetic makeup as well.
Biologists have long seen culture as a type of blanket that insulates humans against many selective pressures. For example, people who live in colder climates simply throw on winter coats instead of having to grow a coat of hair. For most of recent history, scientists thought this buffering action actually stunted human evolution — or even halted it altogether.
The New York Times article says, “Although it does shield people from other forces, culture itself seems to be a powerful force of natural selection. People adapt genetically to sustained cultural changes, like new diets. And this interaction works more quickly than other selective forces, ‘leading some practitioners to argue that gene-culture co-evolution could be the dominant mode of human evolution,’ Kevin N. Laland and colleagues wrote in the February issue of Nature Reviews Genetics.”
Dr. Robert Boyd of The University of California, Los Angeles, and Dr. Peter J. Richerson from the University of California, Davis, are two of the biggest proponents of this theory. The best evidence for culture as a selective force is the lactose tolerance of many northern Europeans.
Shortly after being weaned, most people turn off the gene that allows them to break down the lactose in milk. In many northern Europeans —who are descendants of an ancient cattle-raising culture — the gene remains switched on.
The same culturally based trait was found in three different pastoral African societies. In each of the four cases, a unique version of the gene was found, but the lactose-tolerant result was the same.
The New York Times article also states, “This instance of gene-culture interaction turns out to be far from unique. In the last few years, biologists have been able to scan the whole human genome for the signatures of genes undergoing selection. Such a signature is formed when one version of a gene becomes more common than other versions because its owners are leaving more surviving offspring. From the evidence of the scans, up to 10 percent of the genome — some 2,000 genes — shows signs of being under selective pressure.”
Though many scientists believe the speed of human evolution is rapidly increasing, the genome scans suffer from severe limitations. New evolution or mutations hinder the ability to analyze the signature of ancient selection, and the scans also have difficulty detecting weakly selected genes. If, however, culture has become a major force of natural selection, it would mean that rapid human evolution is the product of our own design — accidental as it may be.