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Why does evolution (namely the evolution of primates into humans) take place both uniformly and universally on the earth? Why aren't there any creatures who have not taken the same evolutionary steps as their same species elsewhere on earth? For example, why aren't there any humans on other parts of the world who look the same as our evolutionary descendants?

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Could you clarify what you're asking a bit? As it stands, it's a little unclear; it sounds like you're asking why there are primates if humans evolved from them. I think you're a little mistaken on evolutionary history. Humans did not evolve from chimpanzees, for example, but rather both species evolved from a common ancestor. See the chimpanzee-human last common ancestor article. So yes, this process is happening, has happened, and will happen again. –  Amory Sep 13 '13 at 22:43
    
@Amory I realize humans evolved from a common ancestor. My question was why does evolution take place at the same rate with the same results to every member of the species all around the world? Why doesn't it vary even dramatically? –  0x499602D2 Sep 13 '13 at 22:54
    
The evolution path a population takes depends on many factors. Environment, random genetic drift, random mutations, population size, population structure, ... If you think of a population that has been splited into two, the two descending population might differ in their initial alleles frequency just after the split or differ by their initial population size. Then environment might differ, the mutation they get might differ, etc... It can drives two initially similar population into very different species. –  Remi.b Sep 14 '13 at 1:56
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Why does evolution (namely the evolution of primates into humans) take place both uniformly and universally on the earth?

Short answer: it doesn't. All human beings descended from the same group of Homo sapiens. There has been some genetic deviation since, but not enough to call it a "species". Evolution happens, but at very long time scales and not at any sort of defined pace.

Read this first.

Long answer: As the link above shows, evolution is dependent on several key factors. Heritable variation and change to selective pressures.

Why aren't there any creatures who have not taken the same evolutionary steps as their same species elsewhere on earth?

Think of humans! Different races, especially ones that have not intermixed, are significantly different. indigenous Africans, indigenous Europeans, and indigenous Japanese, for example. All of these races has genetically diverged into distinct populations with different traits, but the isolation between them hasn't been that long. That's why all humans can still reproduce.

Why aren't there any humans on other parts of the world who look the same as our evolutionary descendants?

Over a very long period of time, Homo sapiens had evolved to become a more advanced, competitively dominant species. although Neanderthals and Homo sapiens did intermix for a while, we're not completely sure how they went extinct. One of the reasons stated is that it's hard for a worse species to exist when a better species comes along.

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My question was why does evolution take place at the same rate with the same results to every member of the species all around the world?

It doesn't. Evolution acts on populations, not individuals. I will never evolve, you will never evolve, but humans are evolving, and sure, certain pockets evolve at different rates. Here's a long but straight-forward write up that deals with perhaps the best example, beak size in Darwin's finches. A select population of birds on an island may be evolving rapidly and differently than that same species elsewhere, perhaps eventually resulting in a divergent species. There is no need for natural selection to operate equally everywhere; in fact, the pressures must be different otherwise we would never see the diverse set of species we do observe.

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