Human ancestors may have begun evolving the knack for consuming alcohol about 10 million years ago, long before modern humans began brewing booze, researchers say. The ability to break down alcohol likely helped human ancestorsmake the most out of rotting, fermented fruit that fell onto the forest floor, the researchers said. Therefore, knowing when this ability developed could help researchers figure out when these human ancestors began moving to life on the ground, as opposed to mostly in trees, as earlier human ancestors had lived.
A lot of aspects about the modern human condition includes everything from back pain to ingesting too much salt, sugar and fat goes back to our evolutionary history. To learn more about how human ancestors evolved the ability to break down alcohol, scientists focused on the genes that code for a group of digestive enzymes called the ADH4 family. ADH4 enzymes are found in the stomach, throat and tongue of primates, and are the first alcohol-metabolizing enzymes to encounter ethanol after it is imbibed.
The researchers investigated the ADH4 genes from 28 different mammals, including 17 primates. They collected the sequences of these genes from either genetic databanks or well-preserved tissue samples. The scientists looked at the family trees of these 28 species, to investigate how closely related they were and find out when their ancestors diverged. In total, they explored nearly 70 million years of primate evolution. The scientists then used this knowledge to investigate how the ADH4 genes evolved over time and what the ADH4 genes of their ancestors might have been like.
Then, scientists took the genes for ADH4 from these 28 species, as well as the ancestral genes they modelled, and plugged them into bacteria, which read the genes and manufactured the ADH4 enzymes. Next, they tested how well those enzymes broke down ethanol and other alcohols. This method of using bacteria to read ancestral genes is "a new way to observe changes that happened a long time ago that didn't fossilize into bones," scientists said.
The results suggested there was a single genetic mutation 10 million years ago that endowed human ancestors with an enhanced ability to break down alcohol