Subject: what are some specifics of the evolution of the races?

What are some of the specifics of the evolution of the races?
We are told that proximity to the equator determined skin color,
which makes sense. But what about the slant of an Orientals eye?
What could have caused this? What about the different skull shapes
and lower leg length differences?

Are new races formed by mixing of races or by adaption to environment
or a combination of both?

How many different races are there, and what are they?

And lastly, can you refer me to the best book that you have read that 
describes in lay terms everything we know regarding the evolution of 
the races?

Re: what are some specifics of the evolution of the races?