Researchers at the University of California Santa Cruz and Arizona State University say in a new study that man's ability to digest starchy foods like potatoes is the main factor behind his evolution to date.
The study says that humans have extra copies of the salivary amylase gene, which is vital to their ability to digest starch. "High starch foods and a high starch diet have been an important evolutionary force for humans," said lead author George Perry, an anthropologist at Arizona State University.
Previous studies have also touched on the ability of man to digest starch as being important in terms of his evolution. However this is the first study to actually find extra copies of genes responsible for digesting starch.
Other animals eat ripe fruits containing very little starch. Researchers say that eating large amounts of starch that could have fueled the human brain and also made available new avenues of diet that eventually led to out colonization of the Earth.
For the study researchers took saliva samples from 50 European-American undergraduates and from 15 chimpanzees. They found 15 copies of the amylase gene in humans, while the chimps only had two copies each.
In the second phase the researchers tested humans and found that people who had high-starch diets tended to have more copies of the amylase gene than those with low-starch diets. The Japanese who eat mainly rice had more copies of the gene as compared to the Yakut population in Arctic, who eat fish.
"We roast tubers, and we eat French fries and baked potatoes. When you cook, you can afford to eat less overall, because the food is easier to digest," said co-author Dr Nathaniel Dominyan anthropologist at the University of California in Santa Cruz.
The details of the study appear in the latest issue of Nature Genetics.
