A "vegetarian" gene may have evolved amongst groups of people who have historically eaten less meat.
A team at Cornell University describes the genetic variation in a study published inMolecular Biology and Evolution -- a variation that they say has "evolved in populations that have eaten a plant-based diet over hundreds of generations". That includes areas of India, Africa and East Asia, with a different variation adapted to a seafood diet found in Greenland.
The adaptation, the team says, allows those with the gene to "more efficiently process omega-3 and omega-6 acids and convert them into compounds essential for early brain development and controlling inflammation". The downside is that it might be linked to some types of cancer and other health problems.
The team looked at frequencies of particular alleles in 234 vegetarian people from India and 311 from the US, finding it in 68 percent of Indians and 18 percent of Americans. This is likely, they say, because Northern Europeans are more likely to eat meat and have "a long history of drinking milk".
Adaptations between vegetarian and seafood diets is most striking -- the vegetarian allele has an insertion of 22 bases, something that's missing entirely from the seafood allele.
"The opposite allele is likely driving adaptation in the Inuit population," said Kaixiong Ye, co-lead author of the paper. "Our study is the first to connect an insertion allele with vegetarian diets, and the deletion allele with a marine diet." "Several studies have pointed to adaptation in this region of the genome. Our analyses combine to show that the adaptation is driven by an insertion of a small piece of DNA that we know its function. Moreover, when it reached the Greenlandic Inuit, with their marine-based diet rich in omega-3, it might have become detrimental," she said.
The team are "unsure" when the adaptation first occurred, as similar analysis of chimpanzee genomes offered no discovery of the vegetarian allele. "It is possible that in the history of human evolution, when people migrated to different environments, sometimes they ate a plant-based diet and sometimes they ate a marine-based diet, and in different time periods these different alleles were adaptive, meaning the alleles have a tendency to evolve under dietary pressures," said Ye.
A recent study from Oxford University found that global adoption of a vegan diet could save more than eight million lives by 2050. Vegetarian diets could save up to 7.3 million, and greenhouse gases could be reduced by nearly 70 percent.