Apparently there used to be white and yellow chinese, but the yellow colored chinese were much hardier and due to natural selection over the years only the Yellow skinned chinese were left. http://books.google.com/books?id=FC...=popular science&pg=PA403#v=onepage&q&f=false
the first few pages were filled with anecdotal reasoning and guesswork. not that I have trouble believing asians may resist blood poisoning better... but I prefer controlled studies.
but a lot of Chinese, especially northern chinese have very white skin. Southerners are more brownish because its a tropical climate
simple if you live in a less than desirable environment, you can either a) develop a high immune system or b) die.