As we're sipping away on a glass of stout or Merlot, we probably take for granted our ability to digest the alcohol in the drink. Alcohol, or dietary ethanol (as scientists like to call it), is technically a toxin — imbibing too much can lead to a hangover and even poisoning, of course.
But thanks to enzymes in our gut, and particularly one called ADH4, we can make use of the calories in alcohol. And, according to a new scientific paper, we gained that ability a very long time ago, at a critical moment in our evolution.
Matthew Carrigan is an evolutionary biologist at Santa Fe College in Gainsville, Fla., and lead author on the paper. He discovered that the ADH4 enzyme started showing up in the ancestor we share with chimps and gorillas 10 million years ago, around the time when these ancestors started eating fallen, fermented fruit off the forest floor. The findings appear in the latest Proceedings of the National Academy of Sciences.
That was a long time before we started making alcohol ourselves around 7,000 BC. And the timing was important, says Carrigan, because 10 million years ago, the climate was changing rapidly, and the East African forest ecosystem where our ancestors were roaming was replaced with more fragmented forests and grassland ecosystems. The change meant our tree-loving ancestors were probably spending more time on the ground.