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..
It was the Senate that appointed a consul to rule the Roman Republic as an emperor for one year. The Roman Republic lasted for 482 years (510 BC -23 BC) until a series of civil wars caused its insurrection into the Roman Empire with a Principate form of government.