Lesser genetic diversity is always bad for survival: with clonal species like the bananas we cultivate, for instance, a single pathogen can endanger the whole population.
The less diverse the population, the less likely timely mutations will help protect it. Incidentally, our modern society is pretty diverse, especially as we protect those who couldn't otherwise survive without modern medicine.
No disagreements there, but adaptations that are advantageous for the population as a whole won't necessarily spread through a population.
https://www.lesswrong.com/posts/QsMJQSFj7WfoTMNgW/the-traged...
Ah, I better see your point. Well, that adaptation has to be selected for at some point of course.
Among a single species, with a 50/50 split of a genetically diverse and homogeneous population, if you eliminate 10% of the former and 75% of the latter, the split becomes 80/20. If that distinction stemmed from genetic factors, you have selected for diversity.
Genetic diversity isn't only advantageous to the population. It's advantageous for the individuals that carry it, depending on the circumstances. Therefore it can easily be selected for.
Surely if genetic variation is introduced primarily by the breeding process, any factors which have a effect against like (competing for food, less genetic variation), etc, are going to get selected against? I have always thought this was the reason behind human lifespans - in neolithic times, up to 33 years. Just enough time to mate and raise another individual to maturity.
No, medium 33, some could get old. Just not most. And median and medium got dragged by high child mortality.
What is "medium"? I know median and mean.
That sounds like group selectionism. In what circumstance would this be deleterious to the propagation of that individual's genes?