Would humans have evolved into different species of humans? (Neanderthals, anywhere, comparison)
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All humans migrated from Africa to different parts of the world. And that led to people looking differently. Later on these humans travelled to different parts of the world, meeting each other again.
However, what if the continents would have been so separate that we would have never met. Europe would have remained Caucasian, and so on. And we would have continued to evolve, yet never met our family (humans on other continents). Would we eventually have evolved into different species? Species so different that mating would be impossible, like the big cats, or snakes.
I think that is what did happen. At some point in a very distant past, humans wandered into the Americas, and for many, many millennia they remained isolated from the Eurasians they left behind. The re-mixing occurred only in the last 500 years and mainly, on only one continent.
Even those many thousands of years were not enough for people in America to cease to resemble the Central Asians that fostered them. The length of time H. sapiens has been in existence is not enough for natural selection to have evolved a different species merely through non-contact.
Different species are ordinarily defined as organisms that cannot reproduce together. Any two organisms that can reproduce are, by convention, deemed to be of the same species, although I suspect somebody will point out an exception to this.
(Miinor grammatical point: You're talking about people "looking different". To "look differently", they would need to use some organ other than their eyes, or to use different evaluative criteria for judging things that they observe.)
All humans migrated from Africa to different parts of the world. And that led to people looking differently. Later on these humans travelled to different parts of the world, meeting each other again.
However, what if the continents would have been so separate that we would have never met. Europe would have remained Caucasian, and so on. And we would have continued to evolve, yet never met our family (humans on other continents). Would we eventually have evolved into different species? Species so different that mating would be impossible, like the big cats, or snakes.
Given enough time and 100% separation, yes. Geographic isolation is an important part of evolutionary theory.
But it takes FOREVER. The common ancestor of cats and dogs are the Miacids, which lived 30-60 million years ago, and cats/dogs are really very similar if you think about it.
Humans move around a lot though (it's how we got all over the world in the first place!) so it's highly unlikely that our species would remain isolated long enough to become different species. No ocean is too wide, no mountain too tall for those creative monkeys to be contained longer than a few thousand years at a time.
All humans migrated from Africa to different parts of the world. And that led to people looking differently. Later on these humans travelled to different parts of the world, meeting each other again.
However, what if the continents would have been so separate that we would have never met. Europe would have remained Caucasian, and so on. And we would have continued to evolve, yet never met our family (humans on other continents). Would we eventually have evolved into different species? Species so different that mating would be impossible, like the big cats, or snakes.
Well, you are talking about two time scales that are vastly different. There may have been little significant interchange between European and sub-Saharan Africa for 70,000 years ago. Possibly 40,000 years between Europeans and Asians, and the migration across the Bering Peninsula into the Western Hemisphere was 15,000 to 20,000 years ago.
These migrations involved relatively small numbers of people, as it is believed that world population only reached 1 million about 12,000 years ago.
Comparison of the DNA of Neanderthals and Homo sapiens suggests that they diverged from a common ancestor between 350,000 and 400,000 years ago. Yet they were still interbreeding with modern humans between at least up to 50,000 years ago.
The kind of evolutionary time period that makes mating impossible could take a million years or more.
Modern Humans managed to walk to every corner of the world (except for islands like Hawaii and Iceland) from Africa in 50-60 thousand years. If they could still interbreed with Neanderthals in over 300,000 years of separation, it would take some impenetrable geographic barriers to keep people isolated for the necessary time for them to evolve into different species.
Given no interference from civilized man, even the land bridge between East and West hemisphere may have opened up again in hundreds of thousands of years.
Thanks for all the responses so far. Although I appreciate the musings about how people are capable of moving pretty much anywhere and thus would meet and interbreed anyway, the question I asked is theoretical.
Also, I once heard that once a species splits of it takes roughly 2.5 million years before they cannot interbreed anymore. Which is why tigers and lions can still breed.
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