Genetics of Alcoholism Dates Back Millions of Years

New genetic research suggests that humans and their ape predecessors may have been consuming alcohol for 10 million years. Homo sapiens’ ape ancestors long ago evolved to eat fermented fruit.

Alcohol, called ethanol by scientists, can be a toxic chemical. And humans’ ability to tolerate drinking relies on one enzyme, ADH4, the researchers explained. Their new study suggests that primate ancestors developed a gene mutation to produce ADH4 beginning about 10 million years ago. This enabled them to safely consume the naturally fermented flesh of rotting fruit when other food sources became scarce.

Matthew Carrigan, an assistant professor in the department of natural sciences at Santa Fe College in Gainesville, Florida explained, “Because fruit can naturally ferment, we may have adapted naturally to the consumption of these foods.”

Carrigan’s finding might change the way scientists look at both alcohol and human evolution, he added.

He said that at the same time our adaptation to ethanol took place, our ancestors also adapted to life on the ground. The adaptation from primarily tree dwelling existence to a terrestrial existence meant that they were being exposed to fruit which is older, and more likely fermented. He speculates, “But basically it suggests that we adapted to ethanol simply so we could tolerate it.”

The findings might even offer new insights into alcoholism, Carrigan suggested. How a particular person’s genes deal with alcohol might give clues to alcoholism prevention and treatment.

If ethanol has been a beneficial and important part of our diet for some time, he questions, then how does this understanding affect our thinking about alcoholism.

Carrigan says it is important to appreciate that there is natural amount of diversity in the differences of genes in each individualh. “And understanding these differences — and how these differences might affect a person’s risk for addiction — could be really important when trying to understand how people interact with ethanol differently.”

Friends Trump Protective Qualities of Anti-Alcohol Gene

There are some people that have a gene variant that prevents them from feeling the desired effects when consuming alcohol. When a person ingests alcohol their body goes to work to metabolize the chemical. For those that have the gene variant, their bodies produce large amounts of Acetaldehyde, which causes the person to feel unpleasant side effects from drinking, mostly headaches and vomiting. Due to this reaction, people who have the gene variant are less likely to drink as much as those that do not have it.

However, there is one thing that researchers noticed trumped the effects of Acetaldehyde in the body, and that was friends. People, especially teenagers, are more likely to ignore the negative effects of drinking if their friends are drinking as well.

Despite initial discomfort, researchers noticed that if a teen chose to drink despite the variant, eventually the negative would disappear and they would react to the alcohol just like those that do not have the genetic quality. “Young people with this protective variant in the alcohol dehydrogenase gene, ADH1B, had a lower risk of becoming intoxicated and developing early symptoms of alcohol use disorder. But when in a high-risk environment – that is, if they reported that ‘most or all’ of their best friends drank alcohol – the gene’s protective effect essentially disappeared,” explained Emily Olfson, a researcher on the study.

It is quite common that teenagers are put in situation where alcohol is around and being offered to them. For those who have the protective gene, alcohol may never become an issue. The person may go their entire life never being interested in alcohol. However, it is clear that the gene’s protective qualities only go so far.

The results of the study prove one thing for certain, it is important that teenagers surround themselves with friends who do not encourage underage drinking. The effects of peer pressure can never be underestimated and this study proves that peer pressure can even trump genetics, just as people who may be more susceptible to addiction don’t automatically become addicts.