Man's ability to digest starchy foods may explain the success of the human race according to a recent research. Compared with primates, humans have many more copies of a gene for the enzyme amylase which is responsible for breaking down starches. The authors speculate that the extra calories that came from starches may have been crucial for feeding the larger brains of humans. Previously, experts had wondered if meat in the diet was the answer. However, Dr Nathaniel Dominy and colleagues at the University of California Santa Cruz argue this is improbable.
"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."
They discovered humans carry extra copies of a gene, called AMY1, which is essential for making the salivary enzyme amylase that digests starch. In addition they found that human groups with high-starch diets tended to have more copies of AMY1 than individuals from populations with low-starch diets: the Yakut of the Arctic, whose traditional diet centres around fish, had fewer copies the Japanese, whose diet includes starchy foods like rice.
The researchers believe 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. In work earlier this year, 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.
Professor John Dupré, a professor of philosophy of science at Exeter University urged caution. He said it was impossible to conclude that the introduction of starchy foods into the diet lay behind the emergence of larger brains in humans. "Lots of things differ between ourselves and our closest relatives and apart from the difficulty of establishing the relative places in the evolutionary sequence of any of these, the assumption that there is any one fundamental to such change is dubious. The results on amylase genes are quite interesting, and a good indication of something we are beginning to appreciate more widely - the functional plasticity of the genome."
An interesting idea but I suspect Mr Dupré is probably correct to say that will be impossible to prove that starches led to the rise of Homo. Still, it’s not as preposterous as the Italian idiots who recently suggested a link between Down’s syndrome and people from East Asia.