Q. about evolution and ancestors of modern humans

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First off, let me just say that I accept the theory of evolution, and I am not a Creationist. But I have questions, including the following..

Now, you'll sometimes hear a Creationist asking a biologist, "if humans came from chimpanzees, why are there still chimpanzees?"

And the biologist will answer, "it's not that humans came from chimpanzees, it's that both humans and chimpanzees share a common ancestor, which at some point in the past diverged into two separate lineages".

At this point I often want to butt in with almost the opposite question to the initial one, and ask, "why is our common ancestor not around anymore?"

I mean, it would be theoretically possible for one species XYZ to still be around at the same time as two other separate species that have species XYZ as a common ancestor, wouldn't it?

Say you have a species XYZ in one place. A subset of species XYZ head north, and through the founder effect, genetic drift, and mutations eventually become a different species. Another subset of species XYZ head south, and also eventually become a different species. But the rest of species XYZ stay in the same place and remain almost unchanged genetically for generation after generation. Is this theoretically possible, or is there some law of biology saying it isn't?

I'm no expert, but I would have thought it entirely plausible that our ancestor once did co-exist with us, until it became extinct due to being less well-adapted to the environment at the time than we were.

There is no "law" against it. If all three species dont come into competition by occupying far apart geographic locations, than all three might propagate.


The common ancestor of both chimps and humans was forced to compete with chimps on one hand, and with australopithicines (proto human apes) on the other. Lost out to both. Both daughter species were better adapted to differing niches in the changing environment. Thats most likely. Or differing populations of the common ancestor simply evolved into the two daughter species. You could view it that way.

I am into evolution as a hobby sortof. I have read a few books on genetics, and read anything I can find about human origins. Here are some things you may not know:

1) There used to be multiple humanoid species at the same time. We killed them off for the most part, and interbred with some. Neanderthal DNA is more prevalent in East Asian populations than any other.

2) The theory is that Chimps, Humans, and bonobos split some time ago. We were divided by a river. Bonobos got on the side with plenty of food. Chimps and humans got on the side with less. Chimps and humans became more aggressive to their own as a result.

3) We have DNA evidence that almost all of humanity was wiped out about 70,000 years ago likely due to a Supervolcano in modern day Indonesia. They can trace it with mitochondrial DNA that only passes from mother to daughter that there was a limited amount of women left. Its though that only a few thousand humans remained after that and we survived near modern day Zanzibar. As a result of this, humans are genetically more homogenous than almost any other species.

4) One thing to think about when a new species is created, there really isn't a clear dividing line. The "new" species can interbred and spread genes to the old. Its only when populations become distinct enough that they can't interbred that a true species is created. Whatever was before humans either interbred or was killed off. Thats why it doesn't exist anymore.

5) For most of human history, progress was held back by constant infighting between men to get women. We have strong evidence that until about 7-8,000 years ago most men did not reproduce whereas most women did. We have current evidence that primitive societies spend a lot of time warring with each other over women.

What changed? Well probably farming. With farming now you can settle down and form larger bands of humans more than simple hunter gatherers. But a larger band of humans now can't function if a few men are hoarding the women. Look at what happens when societies try to have older men hoard the women (like Mormon fundamentalists). The end result is always the same, collapse.