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..
Roman Empire. Roman Empire, the ancient empire, centred on the city of Rome, that was established in 27 bce following the demise of the Roman Republic and continuing to the final eclipse of the Empire of the West in the 5th century ce. A brief treatment of the Roman Empire follows. For full treatment, see ancient Rome.