I think, therefore I harm
During the next few days, if you’ve not already begun, you will enjoy alcohol. A lot of it. But why?
Alcohol is a toxic substance that we use to disinfect, as it kills germs and microbes. It’s a sure way to kill most animals and plants, and pretty much any form of life. Humans, however, developed the ability to resist alcohol and even enjoy it, a trait that we share only with a few other superior apes.
We metabolize alcohol. That is, we have organs and enzymes in our body able to decompose alcohol into simpler elements. Part of alcohol is transformed into sugar, which we are able to use for energy and store as fat. The rest is quickly filtered out of the blood stream.
A dog, for instance, cannot metabolize alcohol. Even a small amount of alcohol will make a dog drunk for hours on ends. Alcohol, a complex substance, will only be filtered out from their body through a very long process. A moderately large amount of alcohol will likely kill the dog.
Alcohol comes in different forms. Ethanol is one type of alcohol which is produced from fermentation of sugar from fruits, and this is the type we consume. ADH4 is the main enzyme responsible for metabolizing ethanol. Present in our stomach and throat and on our tongue, it is the first ethanol metabolizing enzyme to encounter any alcohol we may ingest, and thus digestion of alcohol begins very early. ADH4 comes in different forms though, and only a small subset of these is able to metabolize ethanol efficiently.
In a study which began in early February, a team of scientists first extracted the ADH4 enzyme from different species of mammals to determine their efficiency on oxidizing ethanol. They found that three species had the ADH4 variant that had a significant efficiency: chimpanzees, gorillas and humans. Other mammals, and notably other primates, did not have the right variant. Interestingly, all of these three mammals are very close together from a genetic standpoint. The team then used the fact and correlated it with other historical knowledge to draw a complete story.
About 10 million years ago, our planet went through a major climate change which made a dramatic impact on our landscape. Many ancient species had to go through major adaptation to survive, and those that failed to adapt to the changing world went extinct. It is believed that around that time, a new branch of primates diverged from orangutans – the most arboreal of all great apes – and began spending more time on the ground. With the forests yielding place to grasslands, living an entire life in the trees was now very difficult. The new species would have walked the ground and found new sources of food.
It is believed that the new primate species would have quickly evolved a new variant of ADH4 able to process ethanol efficiently. The change would have permitted the species to eat rotten fruits from the ground, which may often have begun fermenting. The alcohol-resistant gene would have given them a major advantage, giving them the chance to eat from a food source which would have been toxic to other species when other food sources would become scarce, possibly a seasonal event. This single mutation may have saved the species from extinction.
Salt, sugar and fat are all substances that we enjoy. They were essential to our subsistence, but they were scarce. We likely begun enjoying the taste of these as a mean to ensure we would seek them and consume enough of them. However, as our world changed, we failed to adapt and now that we have too much of these, we see a notable increase in illnesses associated with abuse of these substances. The same applies to alcohol. We likely evolved to enjoy alcohol as using it inferred a notable advantage: the ability to ingest food that was toxic to others in periods of scarcity. Alcohol was rare, but soon after we begun agriculture, about 9000 years ago, we begun fermenting fruits to produce alcohol, and eventually distilling it into pure alcohol. A sudden increase of alcohol in our wold led to many illnesses linked to the substance, such as alcoholism and cirrhosis.
The team who focused on the aforementioned study was mainly interested in how alcohol came to us and its effects on our world. Though they believe that being able to metabolize a small amount of ethanol was an advantage to us millions of years ago, they believe that the recent increase of the substance in our world didn’t let us enough time to adapt to consumption of large amounts of alcohol, which explains the resulting illnesses.
They believe that rotten fruits were not a first choice for our ancestors, which rather consumed them when their first choice of meal was infrequent. Our ancestors thus never adapted to a life of daily alcohol consumption.
During the festivities which just begin, please enjoy your drinks like our ancestors did. But do it safely and moderately. And please, remember that we never evolved to drive under the influence of alcohol. Enjoy your holidays and return to us safely in 2015.