If you're interested, I'd highly recommend The Selfish Gene, by Dawkins. It's not a book about a gene that makes a person selfish, but instead how genes themselves are selfish replicators. It's a look at evolution from a very different perspective (at least from how I thought of it before I read this book).

"society's elimination of natural selection also allows other potentially undesirable traits to perpetuate"

True, and that may lead to problems. At the same time, I think the evolution of culture has made certain traits more valuable and beneficial - for life and the ease of suffering - where such traits could not have survived the harsh necessities of life in the wild.