Did Humans Start Drinking Alcohol Ten Million Years Ago?
As we all lapse into boozy Christmas comas on the couch in front of the TV, some of us might be woozily remembering headlines that proudly stated “Humans have been drinking alcohol for ten million years“.
Is it true that humans have really been on the sauce for ten thousand millenia? And how can we know? It might seem like that bottle of Cinzano at the back of the drinks cupboard is pretty old, but not that ancient.
These headlines are based on research published in the Proceedings of the National Academy of Sciences. Before we go deconstructing these stories, let’s get our facts right on a few things first.
What do we mean by “Human”?
The first thing to note is the difference between how laypeople use the word “human”, and how anthropologists use it. “Human” is our common label for homo sapiens sapiens, i.e. modern humans. Anthropologists use “human” to describe any species in the genus homo – homo erectus, homo habilis, homo neanderthalensis and so on. The only remaining species in the homo genus is homo sapiens – us.
The researchers looked at hominids, a larger group which includes the homo genus and our closest primate relatives, such as chimpanzees (from the genus Pan) and gorillas (from the genus Gorilla). You might hear this group referred to loosely as “the great apes”.
So before we get into the story, let’s get the timeline set up. Primates can be traced back to about 65 million years ago – they came into their own after the dinosaurs became extinct. Around 15 million years ago, the hominids appeared as a distinct subgroup of primates. Around 4-8 million years ago, the Pan and homo groups split away from each other. After millions of years of evolution, the first fossil evidence of homo sapiens appears around 200,000 years ago.
So when the researchers traced back alcohol consumption 10 million years, they are discussing the common ancestors of humans, chimpanzees, and gorillas.
How Can We Tell if They Drank Alcohol?
We’re unlikely to find the physical evidence of alcohol consumption from all those years ago. We can find archaeological evidence of brewing and fermenting from a few thousand years ago, but not millions of years. The only way we can discover if they drank alcohol is whether their bodies were adapted to drinking it.
We know for example that the human body developed the ability to tolerate lactose, as a response to the development of agriculture and the abundance of milk. In the same way, we can investigate at what point hominids developed the digestive machinery to break down or metabolise ethanol (the more scientifically rigorous name for alcohol). Understanding this is important for understanding diseases. Just as we now understand lactose intolerance better, we may understand alcoholism better in the future.
The researchers focused on a specific enzyme – ADH4. Enzymes allow chemical reactions to proceed at a faster rate, and ADH4 is one of the first enzymes in the body that encounters ethanol, and begins metabolising it. Different species of hominid have slightly different genes that provide the instructions for producing this enzyme, so they will be able to process ethanol with varying levels of success.
The researchers created a family tree of ADH4, synthesising its many different forms in the laboratory, and testing their ability to process ethanol. This is a very tricky process – in some cases, they were able to use genes from primates that exist today, in other cases the sequences had gaps that were filled using similar species. By knowing where the primates fit in the family tree, they could construct the ADH4 family tree.
They found that around ten million years ago, the genes that code for ADH4 underwent a change that made ethanol processing 40 times more efficient. It’s not clear why, but it is possibly due to consuming fermented fruit. The researchers speculate that rapid changes in the environment during this period forced hominids to adapt to new challenges. They were likely to be frugivores (fruit eaters) and so would have eaten whatever they could get their hands on, fermented or otherwise. Genes that allowed our ancestors to digest ethanol would have put them at an advantage, and allowed them to thrive.
The researchers were careful to note their study only looked at mutations to genes for one enzyme. Metabolising ethanol requires a series of enzymes to work together, breaking down a variety of products in order. If this isn’t done properly, or there is too much ethanol in the system, the consequence is a hangover (which some of us will no doubt feel this Christmas).
Did the Press Do A Good Job?
Some headlines did a good job of emphasising that the study considered human ancestors, such as Discover Magazine and the Daily Mail. Some stories quickly note this, but subtly hide this from the headline: “Origins of Human Alcohol Consumption Revealed” is an example.
The Mail’s article is a good example of science journalism: they quote the study’s lead author, Professor Matthew Carrigan, and include figures from the article (as well as a handy information box on ADH4). Apart from a suggestive set of images comparing humans and gorillas imbibing beer and fruit respectively, they refrain from painting this story as the origin of drinking deliberately fermented liquid, as the first line of the Mirror‘s article suggests:
Man has been boozing more than nine million years longer than previous thought, according to a new study.
So the usual cocktail of good and bad, but for once this brew is better mixed than usual, and a bit easier to digest after too many sherries.
Carrigan, M. et al. (2014). Hominids adapted to metabolize ethanol long before human-directed fermentation. PNAS. DOI:10.1073/pnas.1404167111