According to the Times: East Asian Physical Traits Linked to 35,000-Year-Old Mutation. This one gene is responsible for three traits which are supposed to be more Asian: more sweat glands, distinct teeth, and smaller breasts.
Gaining a deep insight into human evolution, researchers have identified a mutation in a critical human gene as the source of several distinctive traits that make East Asians different from other races.
The traits — thicker hair shafts, more sweat glands, characteristically identified teeth and smaller breasts — are the result of a gene mutation that occurred about 35,000 years ago, the researchers have concluded.
I do notice that I tend to like warm weather more than cold weather. Could be those extra sweat glands!
According to the article, there are three theories on why this developed. The first theory states that the sweat glands were advantageous, and the breasts and teeth came along with the sweat glands. The second theory states that thick hair and smaller breasts were sexually preferred in the East, the same way blonde hair and blue eyes may have been preferred in the West. The third theory is that all three were chosen through natural selection at various points.