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..
The answer most often given is about 500 years, or from 31BCE - 476CE. The ending of the Roman Empire is just an arbitrary date, usually the year of the first sacking of Rome by barbarians. However, Roman emperors still continued to rule for many years after this. In addition, the Eastern Roman Empire continued for almost another thousand years. The Roman Empire.