New genetic research suggests that humans and their ape predecessors may have been consuming alcohol for 10 million years. Homo sapiens’ ape ancestors long ago evolved to eat fermented fruit.

Alcohol, called ethanol by scientists, can be a toxic chemical. And humans’ ability to tolerate drinking relies on one enzyme, ADH4, the researchers explained. Their new study suggests that primate ancestors developed a gene mutation to produce ADH4 beginning about 10 million years ago. This enabled them to safely consume the naturally fermented flesh of rotting fruit when other food sources became scarce.

Matthew Carrigan, an assistant professor in the department of natural sciences at Santa Fe College in Gainesville, Florida explained, “Because fruit can naturally ferment, we may have adapted naturally to the consumption of these foods.”

Carrigan’s finding might change the way scientists look at both alcohol and human evolution, he added.

He said that at the same time our adaptation to ethanol took place, our ancestors also adapted to life on the ground. The adaptation from primarily tree dwelling existence to a terrestrial existence meant that they were being exposed to fruit which is older, and more likely fermented. He speculates, “But basically it suggests that we adapted to ethanol simply so we could tolerate it.”

The findings might even offer new insights into alcoholism, Carrigan suggested. How a particular person’s genes deal with alcohol might give clues to alcoholism prevention and treatment.

If ethanol has been a beneficial and important part of our diet for some time, he questions, then how does this understanding affect our thinking about alcoholism.

Carrigan says it is important to appreciate that there is natural amount of diversity in the differences of genes in each individualh. “And understanding these differences — and how these differences might affect a person’s risk for addiction — could be really important when trying to understand how people interact with ethanol differently.”