Chimpanzees, humans and drinking wine

You may have seen some recent posts about alcohol drinking by chimpanzees. For example:

• Wild chimps consume the equivalent of two glasses of wine a day
• In the wild, chimpanzees likely ingest the equivalent of several alcoholic drinks every day
• Berkley finds chimps consume same as two glasses of wine daily

The basic claim is that chimpanzees naturally consume alcohol when they eat fermenting fruits in the wild. The conclusion from this is that we probably got our own predisposition to alcohol consumption from the ancestor that we share with the chimpanzees.

This alcohol claim about chimpanzees is like saying: “our cousins drink alcohol and so we do too, because our shared ancestor did”. This conclusion is the one also arrived at in the original science article quoted by the web page references above (Ethanol ingestion via frugivory in wild chimpanzees).

For those of you who are unclear about this situation, consider the above diagram (taken from the Encyclopedia Britannica article: Human evolution). In this diagram, we are labeled as “Homo sapiens”, and chimpanzees are labeled as “Genus Pan”. Evolutionary time in this particular diagram proceeds from left to right, and so our most recent common ancestor (ie. the one from which both humans and chimpanzees descend) is clearly indicated. This is simply the same as saying that my cousins and I share at least one pair of grandparents (through either our mothers or fathers).

It does not follow, however, that my cousins and I share all of our characteristics, and that we inherited them from those shared grandparents.

However, the formal scientific study of evolutionary history, sometimes called cladistics, actually works by observing that one group of organisms has some particular characteristic while their near relatives do not. Consider this next diagram, from my own scientific research on the plant group Lechenaultia. (My own career was as a biologist, in which one of my fields of study was evolutionary history.)

In this case, evolutionary time proceeds from right to left, and particular features of the plants are numbered. For example Character 20 is shown as being shared by the species “formosa” and “chlorantha”, and in this case is therefore inferred to have been inherited from their common ancestor. Similarly, Characters 13 and 17 are shared by them with “linarioides”, while “linarioides” does not have Character 20. It is this grouping of characters that allows the scientist to construct the diagram in the first place.

However, note that Characters 1 and 2 appear several places in the diagram, so that having either of these characters does not automatically make those species closely related, evolutionarily, nor that they inherited these characters from a common ancestor.

So, it does not necessarily follow that chimpanzees consuming alcohol automatically implies that their ancestors also consumed it, nor that their cousins (us) did so in the past, either. We both drink now, but we did not necessarily do so in the past, although this is taken to be the simplest conclusion. 

We would, however, be much better off if we had some more concrete evidence regarding the drinking behavior of our ancestors. Note that the original science article cited above observes: “The earliest archeological evidence for controlled fermentation dates to 9,000 to 13,000 years ago in China and in the Middle East”. This is not really all that long ago, when comparing us to chimpanzees!