The incidence of achondroplasia is higher than expected based on random mutation rates alone, suggesting selfish spermatogonial selection.

“so for example a condr plasia it's due to a a mutation in fiberblast growth factor receptor um and what's interesting is that this condition is not that rare right based on sort of these rare mutations you'd expect this would you know occur maybe about one in 100 million but it turns out this these conditions occur in about one in I think 30 to 50,000 or so so there's sort of the discrepancy based on sort of mutational rate that we expect based on age and the rate that we actually see so the explanation for this is something called Selfish spermatogonial selection”