While UV rays can cause skin cancer, because skin cancer usually affects people after they have had children, it likely had little effect on the evolution of skin color because evolution favors changes that improve reproductive success.
The only problem was that I couldn't remember where I had heard that. In fact, I wasn't all that sure that I was right. I know that the Roman Empire lasted rougly 500 years but how about the Egyptians, the Chinese, the Ottomons, etc. I thought that it would be interesting to explore different empires and see how long they lasted. In another article, I talk about the definition of civilization..
How long did Rome rule the Western world? What area of the world did the Roman Empire conquer and rule? For how long did the Romans rule Britain? Some say 500 years some say 400 years but me, i would say at around 400 years (if you want to be precise it was from 43AD(anno domini) to 410AD).