What are the theories scientists & anthopologist have how the different races of people evolved on Earth?

Answer 1

Regional differences come about because of environmental or cultural differences that effect our reproductive success. Our differences in skin tones is because of evolution. Ultimately the driving force of evolution is reproductive success and while there is a variance in every population the overall tone will drift to what is best suited for each environment over generations. As is seen across the globe, there is the general rule that people who live in equatorial regions are darkest and this blends until artic areas are reached where people are the lightest. Like I said, the reason why this was prehistorically was because of reproductive sucess. For instance at equatorial areas the harsh uv rays from the sun breakdown certain vitamins and chemicals that are active in the operations in the human body. As was pointed out earlier one of these is vitamin B, but the most important chemical that is broken down by sunlight as far as reproduction is concerned is folic acid. Folic acid is crucial to rapid cell development so if an extremely light skinned individuals are habituating in tropical regions the males will experience a reduction in their sperm count, and women would experience more miscarriages because Folic acid is extremely important for foetal development. Conversly, as was pointed out, dark people habituating in northern hemisphere localities will have a reduced absorption of vitamin d which is also important for foetal development and for general health which would cause a reproductive discrepancy that would cause this darker toned characteristic to have been selected against.

Another medical condition that is often pointed at in this discussion is cancer, but in fact cancer has very little effect on reproductive sucess because the majority of cancer ocurrs after reproduction, and as of such, would not effect reproductive success in the same way as the previous examples.

Now skin colour is of course the most obvious example and easy to describe, but all regional characteristics have had success in the past, reproductively speaking, or else they would not be predominant in that population. Some that may have been chosen because of "sexual selection" might be harder to fathom why if you are not from the culture which has been conditioned to favour such characteristics (like the tooth gap in some east African cultures which has become a common hereditary feature), but there are many other environmental examples as well. The Inuit (mistakenly called Eskimos) of Northern Canada, for instance, have been noted for having fewer sweat glands that release into the palms of their hands and soles of their feet. This is another easily described adaptation because obviously in their environment wet palms would lead to an increased incidence of frost-bite which would affect their ability to acquire food and persist in the harsh environment in which they inhabit. Over generations drier palms and feet have been selected for because those individuals who had drier palms and feet found more success and were able to produce more offspring.

*** WARNING CONTROVERSIAL AND SPECULATIVE SECTION COMING UP ***
There is a lot that we do not know about why different groups look the way they do as well. For instance, it has been noted that many modern Homo sapiens, exhibit similar regional characteristics to the Archaic Homo sapiens which preceded them and this has helped fuel the discussions of weather Moderns bread into the regional archaic populations or weather they replaced them wholesale. As it turns out DNA evidence is more convincingly proving that at least one of these groups (Neanderthalensis) was replaced completely which does beg the question of why some Europeans seem to exhibit similar characteristics because if they didn't come from Neanderthal interbreeding then the environment somehow quickly selected for these regional variations in a very short time, evolutionarily speaking, with remarkable similarity. The same is seen in other archaic morphologies when compared to the modern populations, but because of warmer temperatures there has been no DNA evidence discovered as-of-yet to make such a comparison as has been done with neanderthal. But the end conclusion of thinking along this tangent would have to be that regional variations are selected for in a more subtle manner then we realize for these similar characteristics to be able to persist between separate, albeit similar, species within similar regional environments. Although, this final section is a bit speculative and controversial because it could also be suggested that modern Homo sapiens are reconstructing regional finds in such away that they represent the "region" more because of their own biases as they reconstruct skulls and skeletons made up of many thousand bone fragments. It would not be the first time that an archaeologist mistakenly angled the alignment of their bone jigsaw puzzle to see what they want to see.
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Anyways, I hope that I have provided you with some good examples and a good description of why Humans show regional variation in their Phenotypic expression.

Answer 2

Different environments, mostly, along with some random mutations that don't do any harm and that, for some reason, ended up in the whole population. As the above poster mentioned, many of the obvious differences help that particular group better survive their environment. Darker skin protects against the sun, so it's more prevailent in sunnier climates. Lighter skin allows more sunlight to be absorbed to aid in vitamin D production, so it's more common in areas that get less sunlight. Hair color variation could be random, could be attached to other traits that have definite survival advantages, or could have some advantage that we're not aware of.

It's sort of like what happens with families, but on a larger scale. I can tell which members of my family are related to my grandfather by blood, because we all have a very distinctive chin. If we managed somehow to outbreed everyone to the point where the entire US were my many-times-great grandchildren, that distinctive chin would be considered a trait of the US race, along with whatever other dominant or useful genes we pick up along the way.

Answer 3

Human races are classified in accordance to their body stature ,skin color, shape of head,peculiarities of face etc.On this basis humans are classified into negroids,mongoloids and caucusoids.Scientists and anthropologists have theories that Africa was host to the first ever human race.The environment and habitat shaped the traits of each race.For example take the caucusiods.They are said to evolve in Europe.Their common features are that they are pale red or olive oil coloured because of the climate.Their body is well built since nomards of Europe had to get along rocky cliffs and mountains.Since they lived in high altitudes they had enormous lung space and long noses and so on.Each major races have sub classes also ,like celts for caucusoids,eskimoes for mongoloids etc.But as earth evolved races also began to vanish.Marital relations and certain other factors led to the emergence of mixed races.

Answer 4

Google for "founder outcome" and "genetic float." Natural choice has additionally performed a function, with lighter epidermis being preferred in latitudes extra far-off from the equator; and lactose tolerance being preferred in a few populations that saved goats, and/or farm animals and/or different mammals that may be milked. Mate choice can have performed a function within the spreading of the blue eyes alleles.

Answer 5

As for skin color, darker skin protects the skin from cancer, whereas light skin allows it to produce vitamin D. Therefore, near the equator races have evolved that have darker skin color, since they are exposed more to the sun's rays. Farther from the equator you get the vitamin D - producing light skin, since skin cancer does not pose such a great threat.

Also in colder environments you will find that people have a greater volume-to-surface area, which enables them to retain more heat.

Of course with geographical and cultural isolation, there are also differences as a result of genetic drift.

Answer 6

They didn't evolved in the way you may think. They moved about and settled in different areas, then they adopted different ways just as a person would, they changed their ways of eating due to what was eaten, what they wore through what they had to wear. They changed according to the temperature, the seasons, soon, they became different races due to all these changes but, it took thousands of years and many generations.

It's not hard to understand once you think about it.

Answer 7

simple, evolution, or their similarities/differences,
example:
an African meets 2 Americans and other two African, he joins the 2 africans, why? they look the same, it's natural to go to groups which people are similar like you.

do you think a deer would meet up a lion, of course not, they're different

see, a simple answer

Answer 8

Environmental specialization.

Answer 9

They already got trouble at identifying early human immigration routes and dates, so better understanding on human speciations and evolution is difficult to do when your basic data is not even proven yet...