New research concludes that primate ancestors’ DNA evolved so they could consume alcohol more than 10 million years ago. Scientists from the Foundation for Applied Molecular Evolution presented findings February 15, demonstrating that the ability to metabolize alcohol likely originated in a common ancestor of chimpanzees, gorillas and humans.
The enzyme found in the esophagus, stomach and small intestine – alcohol dehydrogenase or ADH4 – breaks down alcohol in the body. Without an enzyme to process alcohol, consuming alcohol could be fatal since alcohol is so toxic to healthy tissues. A flaw in the chromosomes responsible for ADH4 has been linked to alcohol abuse and the disease of alcoholism.
Primates didn't start out as alcohol consumers, they lived in trees exclusively until about 10 million years ago. Some of them developed a new version of ADH4 that persisted through natural selection. The need to be able to break down alcohol probably happened when the primates left the trees and began eating fruit off the ground. Once the food fermented on the ground, the new primate diet began to include alcohol from the fruit sugars. Tree-dwelling orangutans still to this day cannot metabolize alcohol, while wider-ranging humans, chimps and gorillas can, thanks to ADH4.
Chemist Steven Benner reached that conclusion by “resurrecting” the alcohol-metabolizing enzymes of extinct primates. Benner and his colleagues estimated the enzymes’ genetic code, built the enzymes in the lab and then analyzed 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 in Minneapolis. Benner “can re-enact what happened in evolution," said the biochemist.
Researchers started with DNA sequences from 27 species of modern primates, then worked backward. However, Boston University biological anthropologist, Jeremy DeSilva, cautioned, “There’s very little fossil evidence from the general time period when humans, gorillas and chimpanzees last shared a common ancestor.” Scientists debate whether this ancient primate was strictly tree-bound or split its time between the ground and the trees. “This is cool work,” he said. “We’ll be able to evaluate it with better evidence as we find more fossils from that time period.”