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..
Longest lasting empire in history. The Roman Empire is considered to have been the most enduring in history. The formal start date of the empire remains the subject of debate, but most historians agree that the clock began ticking in 27 BC, when the Roman politician Octavian overthrew the Roman Republic to become Emperor Augustus.