[tolbiny]

"The most obvious examples of these differences are skin color and facial features (particularly the nose)"

There were plenty of efforts by anthropologists during the 1960s and 1970s to examine genetic bases for behavior between racists. Many of these were initiated by people who believed that they would find some kind of differences. The results of these studies? Essentially none were effectively completed because the researchers found they couldn't define race by skin color. They found that the spectrum of skin pigments that they tried to use to define "Blacks" overlapped with those that they tried to define as "Whites". the most obvious example of this is the spanish. The average skin color of native spanish is signifigantly darker than (i may be off on these numbers, its been a few years since i looked at this info) the lightest 15% of Africans.
This was while ignoring people of Arabic descent, who further complicate the problem of defining race based on skin color.

"For the purposes of this discussion, race is simply the grouping of peoples that had a long period of reproductive isolation from one another. These two groups, having been unable to mix genes for tens of thousands of years, evolved different gene frequencies and even different genes"

There are groups of Black AFricans who were reproductively isolated from other Africans for longer than white europeans were. The genetic variabilty within africans is greater than the average African is different from the average European. These are the reason why skin color is not signifigant in determining differences in "race".