Human race is the most striking example of evolution in my opinion, not in terms of evolutionary origins, but for explaining the effects of subtle change over time:
A single species separated geographically from it's self, each geographical location was different enough to set different optimal mutations amongst the populous resulting in a divergence from the original population into several unique populations.
Skin color is the easiest one to notice and explain; Humans came out of the jungle and into Africa as very dark skinned people. Driven by the lack of resources, harsh climate and drought a group started to move north into Asia and Europe. During the migration the newly separated population found conditions very different, the sun was less intense in the north and as such it was harder for the dark skinned population to acquire the nutrients they needed from the sun as darker skin has lower absorption rates but requires longer exposure, this meant that it was beneficial for the population to develop a slightly lighter skinned population in order to better absorb the nutrients.
As the population continued north there was at some point a divergence between Europe and Asia, this lead to another shift in necessary skin color, lighter for the population heading into the much cooler Europe and darker for the population heading into the comparatively warmer Asia. This split is believed to have happened around Egypt/Iraq and saw one population going north, another east and one that stayed in place. The eastern travelling population split again around Pakistan, heading both down into India and east into China. The Indian population, being once again in a much warmer condition experienced re-darkening of the skin, the Chinese population ended up eventually lighter because of this. From china the to-be Asians split, a population remaining and some moving down into the warmer south-east Asia and once again developing darker skin color. The population heading into Europe became gradually lighter and lighter as they headed continually towards a colder environment. As well as skin color many other changes were noticed, such as lactose intolerance amongst the Asians.
Now if we stop at this point and hypothesize a world in which the human population was never reunited, how much different would they have to become before the Europeans and Asians were classified as different sub-species of African humans? How much longer would they have to develop increasingly separate genetic traits before the sub-species were classified as a new species all together? 100,000 years? 250,000 years? One thing is certain, had things continued it would only be a matter of time before the populations grew so different that you would not be able to declare them the same species.
A single species separated geographically from it's self, each geographical location was different enough to set different optimal mutations amongst the populous resulting in a divergence from the original population into several unique populations.
Skin color is the easiest one to notice and explain; Humans came out of the jungle and into Africa as very dark skinned people. Driven by the lack of resources, harsh climate and drought a group started to move north into Asia and Europe. During the migration the newly separated population found conditions very different, the sun was less intense in the north and as such it was harder for the dark skinned population to acquire the nutrients they needed from the sun as darker skin has lower absorption rates but requires longer exposure, this meant that it was beneficial for the population to develop a slightly lighter skinned population in order to better absorb the nutrients.
As the population continued north there was at some point a divergence between Europe and Asia, this lead to another shift in necessary skin color, lighter for the population heading into the much cooler Europe and darker for the population heading into the comparatively warmer Asia. This split is believed to have happened around Egypt/Iraq and saw one population going north, another east and one that stayed in place. The eastern travelling population split again around Pakistan, heading both down into India and east into China. The Indian population, being once again in a much warmer condition experienced re-darkening of the skin, the Chinese population ended up eventually lighter because of this. From china the to-be Asians split, a population remaining and some moving down into the warmer south-east Asia and once again developing darker skin color. The population heading into Europe became gradually lighter and lighter as they headed continually towards a colder environment. As well as skin color many other changes were noticed, such as lactose intolerance amongst the Asians.
Now if we stop at this point and hypothesize a world in which the human population was never reunited, how much different would they have to become before the Europeans and Asians were classified as different sub-species of African humans? How much longer would they have to develop increasingly separate genetic traits before the sub-species were classified as a new species all together? 100,000 years? 250,000 years? One thing is certain, had things continued it would only be a matter of time before the populations grew so different that you would not be able to declare them the same species.
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