I'm confused about how the inferences are being made. If genes are found in older people, okay, so what? That doesn't mean anything. But then the article says:

I'm confused about how the inferences are being made. If genes are found in older people, okay, so what? That doesn't mean anything. But then the article says: > But if that were the case, there would be plenty of such mutations still kicking around in the genome. So does that mean the gene is less common in children than parents? If so, what does it matter that older people don't have the gene? Why does age factor into this at all?