Did Alcohol Consumption Help Shape Human Evolution?

While you sip on some festive eggnog or hard cider this holiday season, your body will immediately start working to metabolize and filter that alcohol. Now, new research has revealed that we may have ancestors as far back as 10 million years ago to thank for our ability to enjoy these little indulgences.

That's at least according to a study recently published in the journal Proceedings of the National Academy of Sciences (PNAS), which details how a team of experts traced the origins of humanity's particularly efficient ability to enjoy alcohol.

Our ability to metabolize ethanol - enabling people to consume moderate amounts of alcohol without getting sick - largely relies on the alcohol dehydrogenase enzyme ADH4. As fruits naturally ferment in nature - and some can be accidentally eaten - most primates have adapted to boast this enzyme. However, compared to humans, the common primate ADH4 is far less efficient. It had long been suspected that humanity's hyperactive ADH4 received its super boost a mere 9,000 years ago, when settled humans started fermenting surplus foods.

Thanks to the PNAS study, it was shown that this was not actually the case. Instead, experts reverse sequenced the origins of 19 modern ADH4 proteins and found that a 10-million-year-old ancestor of humans, chimpanzees, and gorillas sported a version of ADH4 that is 40 times more efficient than even the modern primate ADH4.

Matthew Carrigan, who was involved in the study, explained in the journal Science that despite not having developed agriculture or brewing practices, this very early hominid still needed to metabolize ethanol in order to eat fallen fruits that became more accessible as they spent more time walking, and less time climbing through trees.

"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," he said. "You'd be a cheap date."

These drunk ancestors of course would not last long in the wild, having a harder time defending their territory, finding mates, or running from predators. That of course quickly led to only the alcohol-resistant hominids surviving to have children and pass on their ideal trait.

Carrigan and his team argue that not only does this explain why we are so well evolved to consume alcohol, but why we enjoy it. Our brains, they suggest, may have adapted to associate pleasure with alcohol, as fallen fruits were a food source that was to be taken advantage of whenever possible.

"It was hard to get too much of this sort of stuff, so when you found it, you wanted to be programmed to overconsume," he explained.

He adds that this trait may be what helped determine which primates became terrestrial, and which stayed in the trees - a stunning evolutionary revelation.

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