There's this idea that gets perpetuated that women become infertile but men can have babies any time they want. But here is proof that what I suspected has always been true: men are in their prime in their twenties, after that, it's all downhill in terms of sperm quality (and maybe other things too).

This is another reason not to date older men if you want children.

“You produce sperm your whole life, as a guy, so in theory you could father a child in your 90s, but the problem is we know that sperm quality starts to go down from your twenties,” says Dr Jeff Foster..."

“What we say is there’s a rule of three [when it comes to reasons why a couple is having problems conceiving]: one third are men, one third are women, one third we don’t know. It’s almost exactly equal, but it’s the women who always get focused on and tested.”

https://www.theage.com.au/lifestyle/life-and-relationships/sorry-gents-eternal-male-fertility-is-a-myth-20210820-p58kkl.html