2014-12-01. Ability to consume alcohol may have shaped primate evolution.

posted Dec 7, 2014, 9:11 AM by Alan Gould
By Sarah C. P. Williams, Science. For GSS Losing Biodiversity chapter 3. Excerpt: ...desire to consume alcohol, as well as your body’s ability to break down the ethanol that makes you tipsy, dates back about 10 million years, researchers have discovered. The new finding not only helps shed light on the behavior of our primate ancestors, but also might explain why alcoholism—or even the craving for a single drink—exists in the first place. ...the human ability to metabolize ethanol—allowing people to consume moderate amounts of alcohol without getting sick—relies on a set of proteins including the alcohol dehydrogenase enzyme ADH4. ...Matthew Carrigan, a biologist at Santa Fe College in Gainesville, Florida, and colleagues sequenced ADH4 proteins from 19 modern primates and then worked backward to determine the sequence of the protein at different points in primate history. ...the most ancient forms of ADH4—found in primates as far back as 50 million years ago—only broke down small amounts of ethanol very slowly. But about 10 million years ago, the team reports online today in the Proceedings of the National Academy of Sciences, a common ancestor of humans, chimpanzees, and gorillas evolved a version of the protein that was 40 times more efficient at ethanol metabolism. “Around this same time, the Earth cooled off, food sources changed, and this primate ancestor started to explore life on the ground,” Carrigan says. And this new way of life meant that, for the first time, primates started eating not only fruit picked from trees, but also the fallen fruits below. And fallen fruits, when they’re exposed to bacteria in the environment that convert sugars to alcohols, will begin to accumulate ethanol. “If you were the ancestor without this new mutation in ADH4, the ethanol would quickly build up in your blood and you’d get inebriated much faster,” Carrigan says. “You’d be a cheap date.” This easy inebriation, he says, would have been a disadvantage to the monkeys without the mutation, making them more easily get sick—or drunk—off fruit, enough so that they couldn’t defend their territory and seek out food. Primates with the new mutation could get more food, his group hypothesizes, and the gene was selected for in the human and chimpanzee lineage....  http://news.sciencemag.org/biology/2014/12/ability-consume-alcohol-may-have-shaped-primate-evolution.