“Most importantly, Galton and all other eugenicists prior to the 1970s made the fundamental
error of believing that heredity is a means by which nature reproduces organisms. Today we
know that fundamentally the truth of heredity is the exact opposite of this apparently obvious
situation: organisms evolve to reproduce their DNA (the organic polymer that is the
biochemical basis of heredity), not DNA to reproduce the organism. The consequence is that
human males, for example, die more readily than females at all ages thanks mainly to the
effects of testosterone: a sex hormone which reduces ‘fitness’ in the sense of shortening life
expectancy by suppressing the immune system and increasing risky and aggressive behavior
but which is also a key element in promoting true Darwinian fitness: the reproductive success
of the individual’s genes. Males without testes live longer, but cannot reproduce, and so are
of no use to evolution!” (Christopher Badcock, Eugenics)
Put it quite nicely even tho it is an exaggeration. Organisms that cannot reproduce are not entirely useless to evolution. The obvious examples being worker ants. In humans, it would be (strict) homosexual males, even tho they sometimes reproduce (a friend i had in primarily school had his father come out as homosexual when the father was around 40 years old), and infertile people. These people can still help other people some of which may be fertile. They can help in various ways that in the end increases the fitness of those they help. For instance, grandparents may help their grandchildren with school, and thus the children received better grades and wanted to do well in school. This eventually resulted in that the children got good educations which helped them acquire a good mate.
