Between the first edition and second edition of Charles Darwin’s Origin of Species, a phrase slipped in which he rather regretted later. Herbert Spencer — a fervent supporter of Darwin’s theory of evolution — had written that evolution is “the survival of the fittest”. Darwin thought that the phrase was a felicitous one and adopted it himself rather too hastily.
Well . . it isn’t “the survival of the fittest”. Any number of people of varying degrees of fitness can survive. Evolution, rather, is “the non-survival of the unfittest”. More to the point, so long as an unfit person — someone with, say, a deleterious genetic mutation — doesn’t have offpsring and doesn’t pass the mutation on then this is what evolution is really about. And that’s usually done by females not selecting him as a partner.