I see that as daylight has reached my multi-ethnic neighborhood near the 45th parallel of north latitude in the middle of North America, this article about settlement patterns of Homo sapiens has received a lot of upvotes. I'll reply based on the more than fifty replies already posted, based on background reading I've done on the subject, and based on my "natural experiment" of living all over the United States (I have been to all states) and living near the Tropic of Cancer in east Asia.

Essential background reading on this topic can be found in a user bibliography on Wikipedia.

http://en.wikipedia.org/wiki/User:WeijiBaikeBianji/Anthropol...

Any hypothesis about the origin, in deep prehistoric time, of a human characteristic will be just that, a hypothesis, now that we are remote in time from when our ancestors settled the earth. Tracing geographic patterns of gene distribution for genes that are under WEAK selection pressure helps suggest where the founder populations of different regions of the world most likely came from, and there is no longer any serious doubt that species H. sapiens originated in Africa and settled first the Old World (including Australia, which required sea-crossing canoes to cross the Wallace Line) and then the New World, with islands such as Madagascar and New Zealand being some of the last places on earth to be settled.

My ancestors are known to have lived in recent historic times in the region the author of the submitted article mentions the most, the shores of the Baltic and North seas. People in my family line are quite pale-skinned although not invariably blond or blue-eyed. My wife's family are known to have lived in recent historic times in the region spanning both sides of the Taiwan Strait at the edge of the tropics. There is a large difference in annual sunlight exposure between those two regions, but my wife's family is like many families from east Asia in also being quite pale-skinned as a baseline, although always black-haired and dark-eyed. As several of the previous comments have correctly pointed out, there is LARGE variation of skin color in all geographic populations anywhere on earth. Moreover, there is large individual variation in skin color in most individuals subject to lifestyle variations (more or less outdoor activity) and seasonal variations (sunny summers contrasted with cloudy winters). My children's skin color varies over a wide range, with my son who plays the most travel soccer becoming the most dark during the summer and my son who is a hacker staying the most pale year-round.

The deep ancestral condition of all hominins was pale skin. Beneath their black hair, chimpanzees (Pan troglodytes) have pale skin at birth and in youth.

http://www.pbs.org/wgbh/evolution/library/07/3/text_pop/l_07...

http://humanorigins.si.edu/evidence/genetics/skin-color

The hominin line of descent that branched into H. sapiens had to develop skin that began dark and persisted as dark as humans lost body hair and began living in savannah environments with less shade than forests, according to the currently accepted hypothesis. As population bottlenecks in Africa formed the species H. sapiens, presumptively the typical skin color of all modern humans was dark (within a pattern of continued variation among individuals and a continued capacity for individual skin color to vary over the course of seasons). Then as different founder populations settled in Europe (high latitude) and east Asia (cloudy even when not at high latitude in many coastal areas), the local populations were under selection pressure for selective sweeps of mutations that increased the gene frequency of paler skin. Generally, both Europeans and east Asians are pale, but they aren't usually pale because of the same novel gene patterns.

By the way, the "race" categories that are used in the United States are arbitrary, subject to rewriting from time to time for political considerations, and do not correspond to any scientific view of geographical populations. In any event, it is clear that human beings have been traveling back and forth and exchanging genes from one local population to another from the earliest days of human settlement of the earth. For more on the specific "race" categories in United States law and how they are applied to specific situations (especially college and university admission), see

http://talk.collegeconfidential.com/college-admissions/12282...

for FAQ links to many official websites with governmental regulations and definitions and statistics.