Taste for alcohol originated 10 m years ago
The event took place perhaps when this ancestor became more terrestrial and started eating fruits fermenting on the ground. Chemist Steven Benner of the Foundation for Applied Molecular Evolution in Gainesville, came to the conclusion by “resurrecting” the alcohol-metabolising enzymes of extinct primates. Benner and his colleagues estimated the enzymes’ genetic code, built the enzymes in the lab and then analysed how they work to understand how they changed over time.
“It’s like a courtroom re-enactment,” said biochemist Romas Kazlauskas of the University of Minnesota. Benner proposed the idea to “re-enact what happened in evolution” at the annual meeting of the American Association for the Advancement of Science.
Today, humans rely on an enzyme called alcohol dehydrogenase 4, or ADH4, to break down ethanol. The enzyme is common throughout the oesophagus, stomach and intestines, and is the first alcohol-metabolising enzyme that comes into contact with what a person drinks.
Among primates, not all ADH4s are the same - some cannot effectively metabolise ethanol, ‘ScienceNews’ reported. To see how ADH4 evolved, Benner’s team read the stretches of DNA that make ADH4 in 27 modern primate species, including lemurs, monkeys, apes and humans.
Then they mapped the DNA sequences on a primate family tree and inferred what the genes might have looked like long ago at points on the tree where evolutionary branches separated. The branching points represent extinct primate ancestors.
Most primate ancestors would not have been able to metabolise ethanol, the results showed. But at the branching point leading to gorillas, chimps and humans - which represents an ancestor that lived roughly 10 million years ago - the enzyme becomes a powerful alcohol digester.
Compared with earlier enzymes, this one was 50 times as efficient, Benner reported, and was nearly capable of breaking down the level of ethanol found in modern alcoholic beverages.