Selfish spermatogonial selection can explain why some mutations are more common in older men.

“so what this suggests is that some of these mutations that occur randomly occur in proliferation Pathways and so it gives the sperm that contain these sort of advantages over their you know brothers and sisters that don't have them for example and so then they out compete the other sperm and so they're more likely to lead to a child rather than sort of a random smattering you can actually see that some of these mutations are more common in older men than younger men”