drunk monkeys
December 3, 2014

Our Ancestors Were Getting Drunk 10 Million Years Ago

Brett Smith for redOrbit.com - Your Universe Online

Predominant theories have man harnessing the power of fermentation and beginning to consume alcohol around 9,000 years ago, but according to a new study – our capacity to metabolize alcohol popped up around 10 million years ago.

In the study, published in the Proceedings of the National Academy of Sciences, researchers focused on the origins of the gene known as ADH4, which produces an enzyme that breaks down alcohol in the digestive tract.

Researchers said they had expected to see the gene crop up in our DNA around 9,000 years ago, and were shocked to find that it proliferated in the Miocene epoch, 10 million years ago. The study team said earlier humans may have developed the ability to metabolize alcohol as a way to cope with eating rotting and fermenting fruit they might have come across on the ground. This would explain why tree-dwelling orangutans can’t metabolize alcohol, but ground-dwelling gorillas can.

"Because fruit collected from the forest floor is expected to contain higher concentrations of fermenting yeast and ethanol than similar fruits hanging on trees this transition may also be the first time our ancestors were exposed to - and adapted to - substantial amounts of dietary ethanol,” Matthew Carrigan, a professor of biology at Santa Fe College, told The Telegraph.

To reach their conclusion, the study team looked at genetic data from 28 different mammals, including 17 primates, taken from public databases or tissue samples. In particular, the researchers searched for ADH4 in the digestive tracts of primates that had diverged from humans as far back as 70 million years ago.

The researchers saw that ADH4 was abundant in the gorilla, which diverged from us about 10 million years ago. The gene was also found in our recent evolutionary relatives, including the chimpanzee and the bonobo. The orangutan, gibbon and baboon were found to lack the gene, making them highly vulnerable to alcohol’s toxic effects.

The researchers also found one anomaly – the aye aye, an endangered lemur species from Madagascar, also has the ADH4 gene. The lemurs diverged from us around 50 million years ago and may have independently developed the gene in response to their own interactions with rotting fruit, the researchers said

"This transition implies the genomes of modern human, chimpanzee and gorilla began adapting at least 10 million years ago to dietary ethanol present in fermenting fruit,” Carrigan said. “This conclusion contrasts with the relatively short amount of time - about 9,000 years - since fermentative technology enabled humans to consume beverages with higher ethanol content than fruit fermenting in the wild.”

The study team pointed out that the emergence of ADH4 in humans coincided with the middle Miocene climatic transition, when the fragmented forests in East Africa were switching over to grasslands. This change would have forced our ancestors to come down from the trees and increasingly come across rotting and fermented fruit.

The researchers speculated that our ancestors probably enjoyed the inebriating effects of alcohol, spurring them to harness the fermentation process millions of years later.

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