Reading through the comments so far I got the impression that people don’t discuss biological or physiological issues that much. I'm not in any related field.

Reading through the comments so far I got the impression that people don’t discuss biological or physiological issues that much. I'm not in any related field. So my argument is based on high school biology: sperm-producing cells of an old man have divided many more times than of one in his twenties. And we know that more cell divisions mean more copying errors. It’s not the first time that I see some empirical evidence about defects from older men. So we should take this seriously. The clock is ticking also for men. Early parenthood also has issues as people aren’t necessarily well-developed in terms of personality or haven’t earned much money yet. So, I feel like a sweet spot is somewhere in the late twenties. Sometimes I think having children very early might be pretty good. In some European countries there’s a lot of help for students with children. The advantage is that these children will be going to school when the parents really start their career. I.e., the children are already somewhat independent. Not having a large gap might also help to develop a better relationship with parents. Obviously a 60+ years old father will always just live in another world than his child.