Today I gave my lecture on mammal diversity and evolution in the 4th year vertebrate course. We have been talking a fair bit about paraphyletic groups, common vs. scientific names, and so on. Within this context, we explored the issue of whether we’re “descended from monkeys”, by taking a look at a phylogeny of relevant primates:
The issues that we noted were:
- “Apes”, as defined as orangutans, gorillas, and chimps, but not humans, is paraphyletic. In other words, either “apes” is not a scientifically defensible term or else it must include humans.
- “Monkeys” is paraphyletic, and in particular Old World monkeys are more closely related to “apes” than they are to New World monkeys. (Also, humans and Old World monkeys are equally closely related to New World monkeys).
- We are not descended from any modern “monkeys” or “apes”, rather we share common ancestors with them. (In that sense, the answer is NO to whether we’re descended from monkeys).
- The last ancestor shared by all apes (including humans) would itself probably have qualified as an ape. (In that sense, the answer is YES we are descended from an ape, but not any of the modern species).
- For “monkeys” not to be problematic, it would have to include apes. In that sense, we would be apes AND monkeys. (And, for that matter, we’re also lobe-finned fishes). As above, it may very well be that the ancestor of all monkeys and apes (the very bottom node on the phylogeny) would have been considered a monkey, and therefore YES we are descended from a monkey (but again, not any modern species).
After class, one of my students emailed me a link to this video, which explores the issues nicely. The author takes a cladistic approach and concludes that we are descended from monkeys for the reasons listed above.
What do you think?
Thanks for the post. I deal with this question all the time in evolutionary psychology courses. As you point out, you could say we've descended "from" monkeys in a broad sense. But what is at issue are the assumptions behind such a statement. I think students say we are descended from monkeys thinking that the theory of evolution by natural selection posits that we are directly related to them – because they don't see the distinction between apes and monkeys (nor that humans are classified as apes for that matter).
In the US, consumers must love a chimp because they show up in commercials all the time. But most of the time, they are called "monkeys" by the voiceover. I guess as my students would say, you know what I mean.
Isn't the whole issue really just a matter of the English language? As your tree shows, "monkey" is a phylogenetically meaningless term that English uses to describe small tailed primates and not a clade to themselves. Other languages, such as French don't make the ape/monkey distinction and as chance would have it, French has it right.