If monkeys evolved into people, then how come there are still monkeys?

Factual Questions
21

Try explaining how it might have happened, being sure that the listener is really listening when you explain that it might not be exact, or specifically true, but it is more like the real history of the race than “monkeys evolved into humans” is.

There was a species of primates, in Africa, many million years ago. They spread out over a region that was so large that some of them were very far away from others of them. They lived that way for a million years, and during that time, in one area only those with digestive systems that could digest higher amounts of vegetable material survived, because prey animals decreased in number as hunting pressure increased. During the next million years, as the forest thinned in another area, only those which were able to travel on the ground for long distances survived. Although their prey animals and plants changed, they were still able to maintain an omnivorous diet. After another million years, the two groups were so dissimilar in behavior, and physiognomy, when they met, they were unwilling to breed with each other, even though they were genetically only slightly different, and still biologically the same species. The more ground mobile members of the species found it easier to survive at the very fringes of the forest, while the more vegetarian members found it easier to survive in the densest parts of the forest. After another million years had passed, one group had spread across the plains, adapting to changes in the climate that made dense forest less common. The other group had suffered strong attrition, and now numbered far fewer members, in the reduced habitat.

Twenty six million years ago, climate change became even more intense, and most of both groups, and most of the original variety died out. Only a few of the three groups survived in small areas, over the entire continent. Then the climate moderated, and their numbers began to grow. By this time, there were three types of primates, so dissimilar that they became three species, rather than members of the same species. The least altered, the ones most like the original species were quite rare, having survived only in the regions where climate remained very stable throughout the period being discussed. But, they did survive. The two new species were both very much more common in their respective areas.

Now, one group is nearly identical to the original species. The other two are much different, both physically, and genetically. There are two species which evolved from the original species, but the original species still survives. Which one will eventually have its descendants survive into the modern world doesn’t matter. The original species might survive that long as well. Or, they could be the progenitors of a dozen branches of primate species which do survive, while all three eventually become extinct.

You are not evolving. Your children are not evolving, although the might be mutants. If your mutant children survive, they might have children, and their children might inherit their specific mutation. Since your mutant child doesn’t know that many other mutants, your child will probably try to breed with non mutants. If the mutation doesn’t kill everyone involved, eventually lots of people will be descendants of your mutant kid, and you. They will still be human, assuming you are. The only way they will become other than human is if something isolates them, and changes in genetic inheritance over a large number of generations makes them unwilling, or unable to breed with real humans. Then, after a very large number of new generations, your mutant kid will be the progenitor of a new species. Whether or not your other children survive and leave descendents is immaterial.

Tris

22

If one’s understanding of evolution is limited, then I would say, no, this is not as stupid a question as it might seem. There are two general forms of evoltuion whereby new species are created: anagenesis and cladogenesis. In anagenesis, a population gradually transforms over time. After some time, t, the population may look very different from its parent population. In such cases, the subsequent species will, by definition, replace the older species.

With cladogenesis, new species appear when a parent population splits into two or more subgroups, each of which are genetically isolated from the other. In this case, the populations are free to diverge, and one species essentially begets multiple species. This is the form that is primarily responsible for an increase in diversity over time.

The popular understanding, if one only got as far as “descent with modification” in their evolutionary studies, might be that of anagenesis: the next generation, being slightly superior – better adapted – to the previous generation will replace it. Thus, of we did indeed evolve from ancestral apes in such a manner, we should have replaced them; we shouldn’t currently be co-existing with them.

Of course, the reality is that we did not evolve anagenetically from our ape ancestors. Evolution is, as they say, a bush, not a ladder or chain, so while populations do change and get replaced by subsequent generations, they are also fracturing and creating new populations. This why non-human apes are still around: our particular lineage is bushy. But, of course, we did replace all of our true ancestors. Just as chimps replaced theirs, etc. It’s just that chimps and bonobos and gorillas and such aren’t our ancestors.

23

I’m not so sure about this.

Imagine some homo sapiens flying off in a space ship to colonize some distant star. Life on Earth continues much as it has, but as time goes by the colonists begin to adapt to their new environment, so much so that TPTB decide to classify those colonists as a new species, homo astra.

Now you have homo sapiens and homo astra. If homo sapiens have not significantly changed over that period of time, it is still fair to say homo astra evolved from homo sapiens, yet homo sapiens and homo astra exist concurantly.

24

Yep. And further, there were undoutably many species of monkeys then, so even if one of those species evolved thru anagenesis (see DF’s post) into the ape line that later gave rise to the human line, then there would still be many other species of monkeys that didn’t. And those species would either evlove into something else (most likely another type of monkey) or go extinct.

But also keep in mind that categories like “monkey” and “ape” and “human” are human constructs, and only approximate what happens in nature. As you trace the ape line further back in time, you end up with something that isn’t quite an ape (in the modern sense) but isn’t quite a monkey either. There is no point when a monkey mother gave birth to an ape baby. There was a period of transition when one could make an argument either way that the population should be called an ape or a monkey.

25

Seems to me we were more directly descended from Cro-Magnons and Neanderthals, and they are indeed extinct, GEICO ads notwithstanding.

26

Cro-Magnons are not extinct - look in the mirror. They’re us.

Maybe DF’s namesakes are the simplest example. If a bird population from an island with one type of seed moves, or is blown to, an island with another type of seed they will evolve beaks to handle those seeds. Assuming no major change in the original environment, the original bird population will stay basically unchanged. Thus, new variant while the old is still existent. There may not be speciation in this example, but that is not really important to the concept.

27

Well, if you want an example without speciation, the first Homo sapiens lived in Africa and probably had dark skin (to protect against the sun). Then some of their descendants scattered to other continents, and those that arrived in temperate climates evolved lighter skin (probably to help in generating Vitamin D). So the white folk descended from black folk, but the black folk are still around.

28

But that’s just a naming convention. We on earth will probably always call ourselves Homo sapiens, not matter how much we may change in the future. It’s hard to imagine a scenario when future biologists decide that we’ve evolved into a new species. Perhaps if there was a catastrphic event that destroyed all civilization and sent us back to the stone age for a few hundred thousand years. In that case, though, it’s unlikely that we would remember the term Homo sapiens or what it meant in a scientific sense.

29

Almost, but not quite. The term “Cro-Magnon” is used only for those early H. sapiens found in Europe. No one would call a skeleton from Africa or Asia “Cro-Magnon”. We really don’t know how much they would have looked like any current population of H. sapiens on the surface, even if their general build would be pretty much the same. So, they’re a subset, and you can say that Cro-Magnons are H. sapiens, but it isn’t technically corret to say that H. sapiens are Cro-Magnon.

Also, the poster you responded to said that we were descended from Neanderthals, which is not correct. Neanderthals were a side branch, sharing a common ancestor with us maybe 500k years ago, but we are not descended from Neanderthals.

30

Even better would be to say, “If my grandparents were farmers, my parents were merchants and I’m a lawyer, why are my cousins still farmers?”.

Because your aunts and uncles stayed in the boondocks.

31

We’re discussing monkeys, not chimps.

32

Clearly? I’ve never interpreted it that way. I’ve always been confused why so many people seem to be so adamant in pointing out that we didn’t evolve from apes, or monkeys as the question may be. It’s always been pretty obvious that whatever the common ancestor was, it most certainly would fit with what people mean when they say “ape” or “monkey.”

Far from being clear that people mean that, I think you’re come across as a pendantic stickler if you simply answer the question by pointing out that we didn’t come from anything still alive - that wasn’t the question.

33

Curt: The way I hear it more often is: “If we evolved from chimps, then why are there still chimps out there”?

34

Perhaps, but we might still genuinely be the same species. Suppose that in 2050, human cryogenics are perfected, and we head to the stars in sleeper ships. Ten thousand years later, the folks who went to the other stars have changed somewhat to adapt to their new environments (or just via random genetic drift). By this time, maybe the off-worlders have changed enough that they can’t or won’t interbreed with Earthers. Also ten thousand years later, a person who was frozen in 2050 is thawed out, right here on Earth, and when he’s awakened, he finds the future-Earthers perfectly suitible as mates, and the feeling is mutual, and they have kids. In this hypothetical situation, it’d be perfectly valid to say that the Earth-12050 humans are the same species (Homo sapiens) as the Earth-2050 humans, but that the humans on the planet Aurora in 12050 are a different species (let’s call it Homo aurora) that decended from H. Sapiens.

In actual practice, of course, there’s a shortage of both cryogenically-frozen specimens from ages past and of time machines, so it’s very difficult to determine whether two individuals separated widely in time are members of the same species. But in principle, at least, it’s possible for them to be so.

35

But species names are determined by populations, not individuals. And since populations don’t, in nature, breed across vast expanses of time, it really doesn’t make much sense to apply the BSC in that scenario. Maybe one of our expert biologists can weigh in on this, but perhaps the proper thing to do, scientifically, is to rename both populations once it’s established that they do not or cannot interbreed.

36

Well, in that case, we ought properly to say that we’re a new species every century or so, since there’s no chance of anyone from 2006 Earth interbreeding with anyone from 1906 Earth. But the Biological Species Concept doesn’t rely on any actual interbreeding taking place; it merely requires that, if there were the opportunity, interbreeding would take place. The cryogenics example is merely a way of constructing such an opportunity.

37

No, we needn’t do that. There are two different issues here:

  1. Does the survival and interbreedability of an individual who was cryogenically preserved for thousands of years have anything meaningful to say about whether a past and future population should be considered the same species? I don’t think so, for reasons I already gave.
  1. If a population splits in two, and, after a long period of time, they either cannot or do not interbreed, does it make sense to rename only one of the populations as a new species, or should we reanme both? That answer I don’t know, and I suspect that the BSC has not been in existence long enough for that to be an issue. I could very well be wrong on that, and would be interested in hearing from a professional biologist on that matter.
38

I see no other way to interpret it. The question presupposes that we a) evolved from monkeys and b) that there are monkeys now. I very much doubt that everyone who asks this question means to insert a qualifier like “not the same kind of monkeys, dontchaknow, but different monkeys, but monkeys nonetheless”.

I don’t know that. Are you saying that the common ancestor of a human and a golden lion tamarin looked like something that would look right at home in the monkey house today?

I disagree. The question assumes precisely that. That’s certainly what I meant when I asked the question.

39

How about this? A population of the common ancestor was forced out of the trees and onto the savannnah. Within a couple dozen generations, there would be no difference between the two populations (T for the original group, S for the group that went exploring). But in each generation, natural selection forced new traits in S that allowed for a better chance of survival, so that they changed, in time, to a brand new species. T, however, stagnated because their environment stayed stagnant, and there was no need for them to develope these new traits (or any new traits, for that matter.) Therefore, T, which we could call monkeys, are still here, while S became, over time, h. sapiens.

40

“T” didn’t stagnate-- it evolved, too. In fact we know that “T” left 2 extant species besides humans, if we assume T = common ancestor of humans/chimps/bonobos. And it would be better to call “T” an ape than a monkey.