Human ancestors were able to metabolize ethanol 10 million years ago, around the time that they came down from the trees.

Matthew Carrigan at Santa Fe College in Gainesville, Florida, and his co-workers analysed the gene encoding the enzyme ADH4, which is made in the digestive tract to metabolize ethanol. They studied this gene from 28 mammals, including 17 primates, to trace its 70-million-year evolutionary history.

When they synthesized various ancestral forms of the enzyme, they found that ADH4 from ancestors of humans, chimpanzees and gorillas broke down ethanol much more efficiently than the enzyme from more ancient ancestors.

This change might have helped the hominids adapt to life on the forest floor, where there was probably more fermented fruit than in trees.

Proc. Natl Acad. Sci. USA http://doi.org/xkp (2014)