The ability to metabolize ethanol, the alcohol in modern alcoholic drinks, may have arisen in humans’ ancient ape ancestor as a way to digest fermenting fruit found on the ground. As this ancestor started to spend more time on the ground, the ability to digest any available food presented a significant evolutionary advantage. This ape ancestor lived about 10 million years ago, and is common to chimpanzees, gorillas, and humans.
Chemist Steven Benner and colleagues remade the enzymes ancient primates used to metabolize alcohol, analyzing their genetic code to hypothesize how they might have changed over time. Modern humans metabolize ethanol using the enzyme alcohol dehydrogenase 4 (ADH4). However, not all primates possess the same version of this enzyme, so not all primates can metabolize ethanol. Benner and colleagues made a family tree of primates by analyzing the similarities in the genetic code for ADH4 in 27 different species of modern primates.
The fossil record is still somewhat lacking from the time period when the common ancestor of humans, gorillas, and chimpanzees lived. Because of this lack of fossil evidence, some scientists do not believe that living on the ground and the ability to metabolize ethanol can accurately be linked. However, as the fossil record improves with more evidence, this connection may become clearer.
Written by Alice Metz.