Posted by:
anybody
(
)
Date: March 23, 2017 10:06PM
There is only one race...the Human Race.
http://scienceline.ucsb.edu/getkey.php?key=1138"To begin, it is a fact that people categorize others on the basis of their physical appearance, ethnicity, ancestry, social relations, and the interaction of all of these which we call race. However, race is not a defined term in biology and cannot solely be explained by different groups having different genes. Indeed there is much more genetic variation within any given population of humans than all the variation between human populations. Therefore, genetically, it is the case that humans share much more in common than they diverge. This is why we are all a part of the same species: Homo sapiens. Our perception of people as belonging to different races may then be a product of human psychology rather than biological reality.
But your question still needs to be answered, how do we explain the observed, or phenotypic, differences between different groups of humans? Evolution by natural selection is one means. When modern humans left Africa some 100,000 to 50,000 years ago, they migrated quickly all over the world to climates very much different than where they evolved. In these new conditions, different traits were better suited for survival and reproduction in different areas. For instance near the equator where we evolved, it was beneficial to have darker skin to resist the intense sunlight. However as people migrated to extreme northern latitudes, those with lighter skin (due to random genetic variation) were better able to survive as they could absorb more sunlight needed to synthesize important vitamins.
Lighter skin phenotypes therefore spread in these regions. Another example: people in Eurasia domesticated herd animals like cows and sheep, and eventually evolved the ability to digest milk beyond infancy, whereas people in other regions are lactose intolerant for life.
So over time natural selection has changed the traits of different groups of humans based on their local environment. It is important to note however that not many traits have been selected for, and humans in fact demonstrate shockingly low genetic diversity compared to other primates. All humans share more genes in common than any two groups of chimpanzees for instance.
In brief, I would answer your question by saying that populations of humans have evolved traits that make them suited to their environment, but we have not evolved into different races or even different sub-species. Rather each human is a different expression of the same set of genes, with some expressions more common based on geographical location."
http://www.sciencemag.org/news/2015/04/how-europeans-evolved-white-skinhttp://www.independent.co.uk/news/science/how-europeans-evolved-to-have-white-skin-starting-from-around-8000-years-ago-10160120.html"Europeans have not always been light skinned, and Caucasians are in fact a fairly new development on the continent, relatively speaking.
According to a new study reported in Science Magazine, it has been found that Caucasions are the product of “a patchwork of evolution in different places” across Europe, while scientist have discovered three genes that produce light skin – both of which have played a part in the lightening of Europeans’ skin colour over the past 8,000 years.
Since researchers began to sequence the genome of ancient populations last year, it has been discovered that Europeans today are the product of hunter gatherers and farmers of at least three ancient populations having mixed together during their migration to the continent over the past 8,000 years.
By comparing key parts of DNA across the genomes of 83 ancient humans from European archaeological sites with recent ones from the 1000 Genomes Project, Iain Matheison of Harvard University’s lab of population, and geneticist David Reich, discovered the genes linked to skin pigmentation that had survived the natural selection process across Europe.
When modern humans first travelled from Africa to the continent around 40,000 years ago they had darker skin, which was still seen in Spain, Luxembourg and Hungary around 8,500 years ago.
These humans lacked two genes – SLC24A5 and SLC45A2 – which lead to the depigmentation and lightening of the skin. But in the far north, ancient bodies in Sweden from 7,700 years ago were found to have both these genes, and a third causing blue eyes, meaning they were pale-skinned and blue-eyed.
Once the first farmers from the near East began to arrive in Europe, and who carried both genes for light skin, they began breeding with the “indigenous hunter gatherers”. One of the depigmentation genes became prominent throughout Europe to the point where central and southern Europeans developed lighter skin."
Edited 4 time(s). Last edit at 03/23/2017 10:41PM by anybody.