Humans have different numbers of a gene for digesting starch, probably because starch-eaters who got more of the genes had an advantage. Karen Hopkin reports.
You are what you eat. Or so it’s been said. Well it turns out that what we eat has also influenced who we are. Down to the level of our genes. Researchers at the University of California, Santa Cruz have found that populations of people who eat a high-starch diet harbor extra copies of a gene whose product breaks down starch.
Ok, we all learned in high-school biology that genes come in pairs: one copy from mom, one from dad. In reality, things aren’t always that simple. For some genes we get multiple copies. Such as the gene for salivary amylase, the enzyme that kicks off the digestion of starch. On average, we humans have half a dozen copies of that gene. I say “on average” because not everyone has six. One person could have two, and another could have ten.
What the Santa Cruz scientists discovered is that individuals from populations that eat a lot of starch—potatoes or corn or rice—skew to the higher-end of that copy number spectrum. And they credit natural selection: more amylase probably conferred a fitness advantage to those who were eating starchy foods. Chimps, on the other hand, have only two copies of the amylase gene. Maybe because they’re not bananas about bread.