The Drunken Monkey and You

Why do we booze? Did Humans Evolve to Be Alcoholic? Blame the monkeys in your family tree.

It’s a theory anyway.

According to the drunken monkey hypothesis, the human attraction to alcohol may be the result of evolutionary programming: We have a sensory bias that associates alcohol with nutritional reward. Our monkey ancestors, tree-dwelling fruit eaters in tropical rainforests, associated the smell of alcohol with ripe fruit. Alcohol also stimulates the urge to feed which in turn helped our primate kin to make use of their resources when they were available. This tendency toward fruity libations could have begun as far back as 80 million years ago. As you can see, alcohol is well embedded into human DNA: Nearly all human cultures consume it.

And even our cousins modern chimps may have a taste for the booze.1

(Evidence for this hypothesis is mostly circumstantial and not everyone agrees that such a thing was possible.)

Why Do Humans Like to Get Drunk?

Humans have a long history of altering the consciousness through chemistry. Some cultures believed these changes in consciousness brought them closer to the gods; others thought of it only as the devil’s juice. The ancient Greeks and the authors of the Bible warned of the evils of drunkenness and dependency. Through the ages alcohol has been linked with connotations of pleasure, sociability, and stress relief. Today, about 2 billion people across the world consume alcoholic drinks.

But, what does alcohol do exactly?

Alcohol is a simple molecule with complex effects. It acts on roughly 50 different neural mechanisms that control thought processes, behavior, and emotion. As a depressant and de-stressor, alcohol works physiologically by increasing uptake of the neurotransmitter GABA, the brain’s primary inhibitory molecule. Sending more GABA into your brain is how anxiety medications like Valium and Xanax work. It is also the reason why you stumble and slur if you drink too much.

Alcohol also reduces the uptake of glutamate, the brain’s premier excitatory molecule. Glutamate is a neurotransmitter released by nerve cells in the brain and is important in memory and learning. By creating a slowdown in the brain’s communication circuits, alcohol effects judgment, responses, and coordination. The more you drink, the more these are effected.

The pleasures you feel are because alcohol also releases dopamine into your brain’s reward center. (The affect is stronger with men than women.) The dopamine release triggers a number of other events including the release of endorphins – adding to the high effect – as well as norepinephrine and adrenalin which give alcohol stimulant effects despite its overall effect of being a depressant.

Alcohol excites a brain chemical cocktail that makes the imbiber feel all at once more uninhibited, clumsy, horny, and sleepy.

Substance Seeking

In moderation, alcohol does have benefits: In addition to a euphoric feeling, it also relieves anxiety and stress. Some researchers have argued that there is a long co-evolutionary relationship between the human brain and psychoactive substances like alcohol. The synthesis of neurotransmitters such as serotonin and dopamine, feel good chemicals, require the consumption of substances – such as alcohol and others – to provide the necessary chemical precursor. Human desire for “substance seeking” evolved as a way to aid the release of these pleasure transmitters. For our ancient ancestors, alcohol had the ability to alter the brain in ways that were irresistible: It could generate positive and eliminate negative emotional states. In fact, alcohol can shortcut to the brain’s pleasure center in ways that natural experiences that would otherwise require hard work and risk: The result is the brain signals a huge fitness benefit where one doesn’t actually exist.

But, What If We Are Drunken Monkeys – Then What?

So, what if alcohol does have an evolutionary basis – how does knowing that help us?

Thanks to evolution, and a changing climate, our ancient ancestors gained the ability to metabolize the alcohol in fermented fruit. This allowed them to make use of an otherwise rotting resource and utilize alcohol as calories. This ability to catabolize ethanol also allows us to keep it from building up and becoming a poison in our bodies.

Physiologically, when we ask our bodies to metabolize too much alcohol, we overtax our system. Consequences can include acidosis and hypoglycemia as well as weight gain, fatty liver, obesity, diabetes, high blood pressure, and heart attack.

And the list goes on.2

Today, we have an abundance of alcoholic consumables available to us 24-7. And herein lies the problem: Evolution designed us for scarcity, not abundance. Abundance and overindulgence are killing us. With alcoholism and binge drinking comes damage to organs – brain, heart, liver, pancreas – the immune system, the nervous system, and a significant rise in the risks of cancers – to the mouth, esophagus, throat, liver, and breast. Excessive drinking is a disease of nutritional excess and modern abundance. By directly and artificially fermenting fruit – believed to have begun about 9,000 years ago – we overwhelmed our systems with ethanol levels that never could’ve existed in nature. From an evolutionary perspective, our bodies haven’t had the time to catch up – it could take us thousands more years to fully adapt to alcohol.

All Are Not Created Equal Under Alcohol

Alcohol affects some people differently than others.

Women: If a man and a woman drink the same amount of alcohol under the same circumstances, the woman will have a higher blood alcohol content (BAC). Women have much less of a necessary enzyme in their stomachs for alcohol breakdown as compared to men.

East Asians and American Indians: The enzyme aldehyde dehydrogenase is produced in the bodies in East Asians and American Indians in a form which is far less efficient in breaking down alcohol. This can lead to a poisonous build-up of alcohol and its by-products in the body.

Older Males: Production of the enzyme tends to decrease with age. Older men will tend to become more intoxicated on smaller amounts when compared to younger men. For some reason, this decrease doesn’t affect women.

Menopausal Women: Menopause causes changes to hormones which in turn causes menopausal women to become intoxicated more easily.

People with Liver Damage: The enzyme is also produced less in people with liver damage. This also lowers alcohol tolerance.

Evolution and Pleasure

Per evolutionary theory, humans evolved and advanced through the repetition of pleasurable experiences. When our ancient ancestors succeeded at adaptive behaviors – actions that could help their survival individually or collectively – their brains released pleasure chemicals. Motivations became integrated with our emotions. Actions were taken through a compelling desire. Clearly it worked for them: We’re here.

But for us moderns, to act on every compelling desire may not be always be the most beneficial. These habits – for food, sex, or anything else that might bring us a rush of pleasure – have long ago gone from a survival advantage to a survival threat: Urges can be so compelling they can override a healthy desire for food, sex, and attachment to other people.

Humans are suckers for mind-altering substances. It’s in our evolution. To use such substances demands a self-control – a self-control that all too often must fight against what our very brains are telling us. Still, humans have survived thousands of years of alcohol and its fermentation – we owe it to our ancestors to keep the fight going.

 

  1. https://www.livescience.com/51146-chimps-get-drunk.html
  2. https://pubs.niaaa.nih.gov/publications/AlcoholOverdoseFactsheet/Overdosefact.htm

 

 

You Are the Drunken Monkey: Did Humans Evolve to Be Alcoholic?