Drinking apes hint at evolution of alcoholism

Ape juice: Scientists have observed Chimpanzees drinking alcoholic palm sap © Kyoto University

For the first time ever, scientists have observed chimpanzees habitually drinking alcohol. Does the history of the world’s favourite drug stretch back beyond even the dawn of humans?

The world’s oldest surviving recipe was chipped into a clay tablet 3,800 years ago. Embedded inside a hymn to a Sumerian goddess, it describes a simple method for making beer.

Alcohol has a long and troubled history. Brewing is almost as old as farming itself, and drinking has been central to many cultures’ customs and rituals ever since. Some historians even believe it was the reason humans started to grow wheat.

Yet it is also a toxic substance and age-old source of personal and social problems — so much so that some health experts refer to it as ‘the most dangerous drug in the world’. How did we evolve to enjoy such a potentially destructive substance?

Footage released this week may give a clue to the answer, and suggests that our alcohol habit goes back further even than the history of our own species. A team of researchers from Oxford Brookes have released a paper describing the behaviour of a group of chimpanzees in West Africa, which regularly drinks fermented sap from palm trees — or, as the researchers put it, ‘palm wine’.

The chimps showed ‘signs of inebriation, including falling asleep shortly after drinking’. Yet since the sap is also high in nutritious sugars, they may not have consumed it for its psychoactive effects. Still, the very fact that they were not put off by the alcohol content is significant in itself: to most animals, alcohol is dangerously toxic.

The fact that chimps are unperturbed by the alcoholic content of the sap may support an idea catchily known as the ‘drunken monkey’ hypothesis, which was first developed in 2004. According to this theory, our ancestors first developed a tolerance for alcohol while scavenging fruit from forest floors. Resistance to ethanol would have allowed us to gather fruit even after it started to rot, meaning that humans with a taste for alcohol were more likely to survive. And so the long, often dysfunctional love affair between drink and humanity began.

Driven to drink?

Many of humanity’s unhealthiest vices can be explained by circumstances long ago in our evolution. Sugar, for instance, would have been a rare, uniquely rich source of energy to our ancestors; today, our tastes remain unchanged despite its endless availability. Similar things can be said for salt and fat. If the drunken monkey hypothesis is true, then humanity’s fondness for alcohol might also be explained by an evolutionary glitch.

But some are doubtful about such an explanation. It’s tempting to look to our ancestors and relatives to explain human peculiarities, they say; but our human appetites and behaviours are not just a product of our genes. Our over-consumption of alcohol is a social problem, not a biological one.

You Decide

  1. ‘Humanity would be better off if we’d never discovered how to make alcohol.’ Do you agree?
  2. Is it reasonable to draw conclusions about human behaviour by looking at great apes like chimpanzees?

Activities

  1. ‘Alcohol is as dangerous as any illegal drug, and should be regulated just as strictly.’ As a class, debate this statement and put it to a vote.
  2. Make a public information pamphlet explaining the effects of alcohol on your brain and the risks involved in consuming it.

Some People Say...

“Humans are not descended from animals. We are animals.”

What do you think?

Q & A

If people have been drinking alcohol for so long, surely it’s no big deal?
Wrong. The fact that humans have been drinking alcohol for so many millennia doesn’t make it less dangerous. Alcohol causes at least 3.3 million deaths each year, according to the World Health Organisation — that’s almost 6% of all global deaths. And even when it doesn’t kill people, an alcohol habit can have hugely negative impacts on your life: it can make you more violent, increase your risk of accidents and damage your professional and personal life.
But everybody drinks!
Not everybody, but it is very common in most cultures. If you’re old enough and responsible enough, you may well want to drink as well. Just be aware that alcohol is a drug and a toxin, to be used with care and restraint.

Word Watch

Sumerian
A language used in the Middle East from the middle of the 4th century BC, originally by the Sumer civilisation. It is often said to be the first ever written language.
Most dangerous drug
The British drug expert David Nutt famously concluded that alcohol was more destructive than heroin, using a scale that took into account both the harm it causes to users and the social damage it does. That is a controversial finding, but there is no question that alcohol kills millions of people worldwide every year.
Ethanol
Pure alcohol of the kind that people drink in things like whisky and wine. Its chemical symbol is C2H6O and it is also used as a fuel. Other types of alcohol, such as methanol, have different numbers of carbon, hydrogen and oxygen atoms.
Started to rot
When fruit is left in the open, microbes begin to feed on its sugars, breaking them down into ethanol and carbon dioxide. This is how fermented fruit becomes alcoholic.