Smoking-Gun Evidence of Man-Monkey Kindred: Episode II... Tails

Evolution doesn't usually work by huge jumps in a single generation like that. It is a gradual process - the transition from, for example, early hominids to modern humans took a long time. There was never a chimp who gave birth to a human or anything like that. Rather, there was a population of hominids which changed gradually over thousands of years, eventually becoming more human-like as it went. It broke into several side populations as well, all of which have since died off - which is why you don't see Neanderthals anymore.Plants have produced offspring that can't reproduce with their parents. That is caused by a duplication of the whole genome of the plant, and so the offspring has to reproduce asexually, at least until it has built up a breeding population. In that case, the offspring would be classified into a different species.This message has been edited by Gary, 12-07-2005 02:29 PM

Please read my post from earlier in the thread. I said that animals don't normally evolve by huge jumps in a single generation. There were primitive hominids at one time, then they gave birth to offspring that were a little bit more like humans, but not different enough to make them unable to reproduce. As time went on, the population became more and more like what humans are now, though they had not set "human" as a goal.If the original population of hominids had split into two groups, and they remained separated for too long, eventually the differences would build up and they would no longer be able to interbreed. That is why humans and chimpanzees can't mate with each other.

Why would humans need to exchange genes with apes for evolution to be correct?There is no solid, set-in-stone barrier between human and ape. Now, there aren't any nonhuman hominids left for humans to breed with. There are only our more distant relatives remaining, like chimpanzees and gorillas. The ones that were more like modern humans, like the Neanderthals, all died off.Because there is no solid barrier, there are many transitional fossils in between apes and humans, and it is hard to tell where apes end and humans begin. This is in line with what the theory of evolution would predict. All evolution requires is for the ape-like ancestors to give birth to offspring just a little different from themselves - that is, the offspring has mutations. After many generations, the mutations build up and you have something very different from what you started with.We share around 96% of our genes with chimpanzees. The other 4% is mutations that have built up since the common ancestor between chimps and humans.

You still aren't getting it. There is a continuum between modern species and their ancestors. Even if the animals in between the modern species and its ancestor have all died out by now, at some point there was an animal that you probably couldn't easily put in either the old or the new species. The population at that time could be thought of as being in a transition. The transitional also breeds only transitional animals like itself.If there is a transition, there is no need for humans to breed anything but humans and no need for apes to breed anything but apes. Instead, you have a human-like ape breeding other human-like apes. After some more mutations build up, the human-like ape becomes more human, like with a pelvis better adapted for upright walking, and a bigger brain. Even more time passes, and the brain is much larger than before, and upright posture is perfected. It isn't really clear where to draw the line and say "Okay, this fossil is a human," because the fossils are too similar. They definitely show a progression from more ape-like to more human-like, but you can't see where the ape ends and the human begins.Paleontologists classify their finds into species partly just so that they have a handle to talk about them with. With fossils, it is impossible to tell what could breed with what. So if a fossil seems different from the known fossils in a significant way, it is grouped into a new species. There is often some debate as to where it should be classified, because it is hard to tell whether or not it is different enough to warrant a new species designation. So maybe Homo erectus could breed with Homo heidelbergensis, and the two are actually in the same species. There is no way for us to find out anymore.