Natural selection is the fittest of the fittest surviving. But what does that even mean? Everything survives for a while, like dinosaurs. But, then they die out. So what could be the fittest of the fit if all things die out? Well, it is also said that they become fit because of their genes. But, the genes that are accounted for are the good ones and not the bad ones. Before I can answer that question, the question that arises is what are bad genes? These are genes that make addiction or a mental illness. These are only diagnosed in humans because they are the only ones that can seek treatment for them. Most other animals just die out because there body is going through too much. But, this also raises the point that when Darwin wrote about natural selection that when an animals would not mate with the one that was not fit and they would just allow those genes to die out.  But if this were true nothing would mate with that and there would not be anymore "bad genes".