Did Humans Evolve From Monkeys?

I’m not sure. We do not evolve from monkeys. We evolve from common ancestors with monkeys, right?

That’s the answer that I presumed they were thinking about. But, as @glipsnort says, if we could see the most recent common ancestor we would probably call it a monkey.

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Really? It was certainly not any monkey we still see around today. Even very basally, it is a more intermediate “monkey” than what we see alive today, right?

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That’s the ambiguity of the question. Were they asking about the monkeys that we see around today, or were they asking about earlier animals that we might call monkeys if we could see them.

That does not appear correct. Humans are primates. There are monkey primates and ape primates. We are closer to apes than we are to monkeys.

My point was that if we want to obey the rules of cladistics, then any classifications we use have to be monophyletic clades. Any monophyletic group that includes every extant species classified as a monkey (i.e. both New World and Old World monkeys) also includes apes and humans. (Or rather, also includes apes, since for apes to be monophyletic humans have to be apes. If we’re being properly cladistic.)

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Can’t pass up an opportunity to share this earworm:

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What do you mean by “intermediate”? We are more closely related to Old World monkeys than to New World monkeys. If the term “monkey” means anything, then our common ancestor with OW monkeys was a monkey. That’s cladistic classification. Even if you allow “monkey” to be paraphyetic, that ancestor is still a monkey. Only if you interpret “monkey” to mean “an extant species of monkey” does the answer become “False”.

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Clearly you need more education on phylogenetics and systematics. We are primates. Similarly (identically) we are monkeys and we are apes, and apes are monkeys. Groups within groups. If monkeys are to be monophyletic, apes are monkeys. If apes are to be monophyletic, humans are apes. We are primates, mammals, vertebrates, eumetazoans, opisthokonts, eukaryotes, etc.

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I see what you are saying from cladistics, and even anticipated this. I suppose I’m working through to what extent that ontology applies to the past. Do you think the most recent common ancestors of chimps/humans were like any modern day monkeys?

Well, of course they were like chimps and humans, which are modern day monkeys. But you refer to species we usually call monkeys, not apes. No, they were more like modern day apes than non-apes. But the common ancestor of monkeys and apes was quite a bit like what we usually call monkeys. You really can’t avoid the notion that we descend from monkeys, even if you use the popular notion of what a monkey is. Under that definition, we descend from apes more recently than we descend from monkeys, but “most recent” isn’t what the question says.

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That is what I meant.

I can see what you are saying now.

To what extent where these ancient monkeys similar or different than current day “monkeys” (as distinct from apes and humans)?

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You should realize that monkeys as you think of them are paraphyletic. That means that whatever features you think of as defining monkeys (both OW and NW) must be shared by the common ancestor of apes and monkeys. This might be clearer if we had a cladogram to look at. But think of this: whatever distinguishes apes from monkeys would be synapomorphies of the ape clade, so the common ancestor of apes and monkeys, lacking those synapomorphies, would look like a monkey. To put it in more familiar terms, suppose that the ancestral monkey had C at position 437 in an ADH gene, and apes are diagnosed by G at that position. The common ancestor of apes and monkeys would therefore share the primitive C.

Yes, I get that. Let me give you another way to look at it, that is not inconsistent with what you are saying.

Consider Homo erectus. They are not quite like any Homo sapiens or chimpanzees alive today. There is debate one whether to classify them as “human” or not, in a way that does not apply to any extant “humans.” Looking back into the past, for many important features, we are not sure where they sit in the continuum between us and a Chimpanzee. How much language do they have? How much technology and culture? What is the erectus-condition? Of course there are opinions on this, but there is not a settled answer. Homo erectus sits outside the classification of “human vs ape” we have from only extant animals. In this sense, they really are transitional forms.

So the question is, suing extant forms as a guide, were the common ancestors of humans/aps and human/monkeys more or less monkey or ape or human? Do we have close analogues today, or were they more like Homo erectus, for whcih there is not a clear extant example.

I understand also that we are grouped together all in cladistics. however, as I understand it, the common ancestor of all mammals did not have a placenta. This appears to arise later through convergent evolution in several lines, or at least that is one theory. So there are traits we see in all mammals that are not in our most recent common ancestor. So the first mammal it seems may not have had all the extant hallmarks of being a mammal. I’m asking an analogous question about those from whom we evolved 6 million 10 million 15 million years ago. Where they like extant monkeys or apes, or would they be better described as something different?

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There is no classification of human vs. ape, scientifically. There are only groups within groups, and Homo is a genus of ape. H. erectus is transitional, but not between humans and apes, because we’re all apes. You think this way most of the time: you would never speak of a transition between mammals and humans or between primates and humans. Why should apes or monkeys be different?

This is not a question that makes sense in taxonomic terms. It’s about similarity of particular species rather than group membership. You have wandered far from the subject of the BBC question 5. But if we take it regarding similarity, there’s a way to try answer that: phylogenetic analysis followed by mapping of characters. But then we encounter the problem that “more like” is fairly subjective. Which characters should we look at? The common ancestor of humans and chimps looked more like a chimp in some ways and more like a human in others. There’s also ambiguity in reconstruction. Still we might suppose that characters shared by chimps, gorillas, and orangutans would be the parsimonious bet for that ancestor. Of course the more finely grained your comparison the less likely there is to be a living example, since no two species are identical.

I don’t know that theory. Of course the common ancestor of all mammals didn’t have a placenta; it laid eggs, and there are extant mammals that do that. I think you’re trying to look at the wrong branch. But I’m unacquainted with the idea that the common ancestor of all Theria didn’t have one. Is there a reference for that? While there is certainly a bit of convergence here and there, there seems no reason to believe that the common ancestor of all monkeys wasn’t a monkey and woudn’t have looked like a monkey. Not any living species of monkey, just as two species of living monkeys don’t look alike either, and especially as a vervet doesn’t look just like a tamarin; and yet we consider them both monkeys.

Our best hypotheses, held I think with considerable confidence, would be that they looked like whatever their descendants share in common, and beyond that whatever can be optimized to that branch of a phylogenetic tree. If chimps, bonobos, and gorillas are apes, that ancestor is an ape. Not only is it an ape cladistically, you would call it an ape if you had a time machine to go look at it.

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So it looked like a monkey, and it did not look like a monkey. Our idea of what a monkey looks like comes from what monkeys look like. You would think that would go without saying.

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Hi John Harshman,

What do you mean by “intermediate”? We are more closely related to Old World monkeys than to New World monkeys. If the term “monkey” means anything, then our common ancestor with OW monkeys was a monkey. That’s cladistic classification. Even if you allow “monkey” to be paraphyletic, that ancestor is still a monkey. Only if you interpret “monkey” to mean “an extant species of monkey” does the answer become “False”.

I respectfully disagree. What I would say is that humans, apes and monkeys are all simians, and that humans, apes and Old World monkeys are all catarrhini. I have no objection to saying that we evolved from catarrhini or for that matter, simians.

There is no classification of human vs. ape, scientifically. There are only groups within groups, and Homo is a genus of ape. H. erectus is transitional, but not between humans and apes, because we’re all apes.

I would respond that “ape” is not a scientific term. Humans, gorillas and chimps (including bonobos) are all hominins. Humans, gorillas, chimps and orang-utans are all hominids, not great apes. H. erectus is transitional between early Homo and Homo heidelbergensis (or perhaps Homo antecessor).

You think this way most of the time: you would never speak of a transition between mammals and humans or between primates and humans. Why should apes or monkeys be different?

In ordinary parlance, the term “mammal” simply refers to an animal that feeds its babies milk, while the term “primate” refers (roughly) to a relatively large-brained mammal with opposable thumbs and well-developed vision. Humans are members of this group. The term “ape,” on the other hand, commonly refers to simians sharing certain anatomical characteristics. Look at the following picture: here. You can see that among the hominids, humans look nothing like the rest. That’s why “ape” is a paraphyletic term.

By the way, I thought the BBC quiz was ridiculously easy.

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Why not apply the same reasoning to the word “monkey”? If you do, we descended from monkeys.

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It appears that you contribute nothing to any discussion you’re a part of. Is that how you want to be known?

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Well, of course it isn’t. But the meanings of words change over time. “Ape” used to refer to tailless baboons, once upon a time. The cladistic revolution in systematics is percolating into the language, and when speaking about evolution, it’s useful to refer to “ape” and “monkey” using monophyletic definitions. And even if you use a paraphyletic definition, we aren’t monkeys, but we’re still descended from monkeys, which was the BBC question. The BBC answer is just wrong unless you define “monkey” as referring only to extant species, in which case it’s trivially right.

Perhaps you can see that, but I see that they look very similar. Only an anthropocentric viewpoint that fixes on the smallest differences would claim that “humans look nothing like the rest”.

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