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jeudi, 12 septembre 2013

ALCOHOL TOLERANCE

THE HUMAN BODY PROGRAMMED TO DRINK ALCOHOL FOR THE LAST 10 MILLION YEARS


Claude Gilois

Astonishingly, this is what Dr Bremmer, a chemist from the Foundation for Applied Molecular Evolution at Gainesville, Florida, concluded in a study that brings the ability of primates to metabolise alcohol back 10 million years. Until now, there was a general consensus that our capacity to metabolise alcohol went back to the neolithic era, some 10,000 years ago, the date at which human beings settled down, as before then fermenting alcohol in quantities that could be  consumed by a population required equipment that was not available .

How did Bremmer arrive to such a conclusion that goes against current thinking on the subject? This was achieved by some clever tricks of molecular biology and pretty thorough detective work worthy of Hercule Poirot. Bremmer and his team isolated the genes responsible for the production of the enzyme ADH4, primarily responsible for the degradation of alcohol in the human body amongst 27 of the most common living species of primates.

 

From this data and from the genealogical tree of primate development over the last 60 million years (just after the dinosaurs were wiped out from the earth), they deducted the characteristics of the enzyme ADH4 and its modifications over time. Bremmer and his team then synthesised these enzymes in their laboratory and tested their effectiveness on the metabolism of alcohol.

 

It is very similar to a re-enactment of a crime scene where observations and forensics are brought together to come closer to the truth.  The effects of the synthesised enzymes on the metabolism of alcohol were astonishing. Those enzymes that corresponded to the older primates were, by and large, ineffective for the metabolism of alcohol, but when the genealogical tree divided to form the branch that would produce gorillas and chimpanzees and eventually humans some 10 million years ago, the ADH4 synthesised in the lab was particularly good at metabolising alcohol. It was in fact 50 times more powerful than the enzyme found on earlier primates.  Bremmer also stated ‘This enzyme had nearly the same capacity to metabolise alcohol as the one humans have to-day’.  

 

Primate Family Tree.jpg

We know that gorillas and chimpanzees spend time on the ground and it is highly likely that these primates did the same 10 million years ago, when their capacity to metabolise alcohol evolved positively in a draconian fashion. Bremmer attributes this modification of  metabolic capacity to the consumption of ripe fruits fallen from trees that were undergoing fermentation with natural yeasts. This would explain why orang-utans (the common ancestor of gorillas and chimpanzees and eventually humans) that lived 16-21 million years ago were unable to metabolise alcohol:  orang-utans are never seen on the ground.

 

Anthropologists, very cautious not to underwrite discoveries without studying fossils, concede that Bremmer’s work is pretty cool even if they prefer to wait for further evidence to conclude. But fossils dating back to 10-60 million years are few and far between.

 

Contrary to other toxic substances, in particular tobacco, the human body has the ability to cope with alcohol and is, therefore, less exposed to its dangers and a certain amount of consumed alcohol can be safely metabolised. However, regular consumption of alcohol will engender the activation of the alcohol gene(s) and this activation can easily be transmitted to offsprings.  This ability to click genes on or off  as a result of  surrounding environment is relatively new and is called epigenetic. It is very similar to an electrical fuse box in a house,  clicking a fuse on does not automatically give you light, you also need to click the light switch on. So even if your past history and your environment predispose you to alcohol consumption (your fuse is clicked on) you will not necessarily consume alcohol as you need to switch the light switch on (i.e. consume alcohol).   However, you will have a natural tendency towards alcohol.   If you do not consume alcohol, this gene may get turned off over time as with epigenetics all processes are reversible as there has not been any modification of the chemical structure of the gene.

 

Enough to reassure the addictionologists (addictologists)?   Not really, but enough to give them a good income for years ahead.

 

evolutionpic2.jpg

 

 

 

 

 

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