Every batch of sperm represents an opportunity for genetic typos - called de novo mutations - to be passed on. A 20-year-old man and woman will each pass on about 20 de novo mutations to a baby they conceive. By the time the couple is 40, a woman's total has remained at 20, while a man's has jumped to 65 - and it keeps climbing from there.
Paul McCartney had a baby when he was 61; Rod Stewart was 66; Rupert Murdoch was a stunning 72. Not only does that mean they'll have less stamina than the average dad, that means they'll, well, check out a lot sooner too.
There are a lot of downsides to being male. We age faster and die younger. But give us this: we're lifetime baby-making machines. Women's reproductive abilities start to wane when they're as young as 35. Men? We're good to go pretty much till we're dead.
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