'Starch food fuelled human evolution'

LONDON: Starchy foods has fuelled human evolution on this planet to a large extent, a new study by researchers from the University of California, Santa Cruz, has revealed.

In their study in Nature Genetics, Dr Nathaniel Dominy and his colleagues found that compared to primates, humans are genetically more adept at breaking down calorie-rich starches, crucial for feeding the larger brains of humans.

Previously, experts had speculated that meat in the diet was the probable answer.

Dr Dominy refuted this argument on the ground that meat occupied a small fraction of the human diet even when looked at it in the hunter-gatherer perspective.

"Even when you look at modern human hunter-gatherers, meat is a relatively small fraction of their diet. To think that, two to four million years ago, a small-brained, awkwardly bipedal animal could efficiently acquire meat, even by scavenging, just doesn't make a whole lot of sense," said Dr Dominy.

As part of their study, the team also looked at groups of humans with differing diets, and found that those with high-starch diets tended to have more copies of AMY1, a gene essential for making the salivary enzyme amylase that digests starch, in comparison to individuals from populations with low-starch diets.

For example, the Yakut of the Arctic, whose traditional diet centers on fish, had fewer copies than the related Japanese, whose diet includes starchy foods like rice, the study revealed.

The researchers conclude that our earliest human ancestors began searching for new food sources other than the ripe fruits that primates eat.

"These were starches, stored by plants in the form of underground tubers and bulbs - wild versions of modern-day foods like carrots, potatoes, and onions," the researchers wrote in their study.

Incidentally, in an earlier work, the team found that animals eating tubers and bulbs produce body tissues with a chemical signature that matches what has been measured in early-fossilised humans.

Dr Dominy said when early humans mastered fire, cooking starchy vegetables would have made them even easier to eat.

At the same time it would have made extra amylase gene copies an even more valuable trait, he said.

"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. And marginal food resources can become part of the staple diet. Now you can have population growth and expand into new territories," Dr Dominy said.