problematic z

All humans were dark-skinned until 100,000 years or so ago, skin changes occured during that time due to migrations northwards. Skin pigment genes can change quite rapidly compared to genes correlating to intelligence. Differences in intelligence in races today are caused by differences in culture, social status and parenting.

Hey, but if anyone finds this stuff kind of interesting, check out this book/tv series called Guns, Germs, and Steel. http://www.pbs.org/gunsgermssteel/show/episode1.html

A very good, well researched counter argument to the statement that some races are more intelligent than others.  

@Freya 

All humans do come from a common ancestor as far as we know and thus at some point were all identical as you have said, but later became quite different from admixture with neanderthals and so on. Culture, social status and parenting are not everything. Many, many studies have been done on this including the Minnesota trans-racial adoption study. The studies are often really complex and long so I won't go into them here, I would instead direct you to listen to this video if you have time. https://goo.gl/0O3BjX

@NoSpoonNeo

Guns Germs and Steel is pretty controversial and under heavy debate. A lot of people accuse Jared Diamond's research of being shoddy. Not to mention Native Americans are a bit of a hole in his story. If resources and the quality of the land were really the only factors in determining the success of a civilisation, why were the american indians not as successful as east asians or europeans? Interesting read but not a magic bullet for the genetic argument. http://goo.gl/zb7cRA