Sperm cells form during the process known as spermatogenesis, which in amniotes (reptiles and mammals) takes place in the seminiferous tubules of the testes. This process involves the production of several successive sperm cell precursors, starting with spermatogonia, which differentiate into spermatocytes. The spermatocytes then undergo meiosis, reducing their chromosome number by half, which produces spermatids. The spermatids then mature and, in animals, construct a tail, or flagellum, which gives rise to the mature, motile sperm cell. This whole process occurs constantly and takes around 3 months from start to finish.
Do, for example, 4-6 years old males have sperms that can fertilize an egg? If they don’t have sperms, can their sperm cell precursor be modified in any way (e.g. in lab etc.) to fertilize an egg? Was it ever done?
The youngest mother on record was 5 years old. We see more discussion of precocious puberty in females (as it is more distinctively self-evident, i suppose). But presumably it must happen in males also, and I’m guessing it could be simulated with hormone shots. The only question is why anyone would try and also what to do with/to anyone who does try?
I presume the purpose of puberty is to delay reproduction until the subject has grown to adult size, both for physical reasons of child-bearing (which obviously does not apply to males) and for the associated ability to feed and support their children until they too can fend for themselves.
Puberty also exists so that the child is old enough to channel their sex drive appropriately (in most cases) when it shows up.
It would be extremely unlikely for a preteen boy, let one aged 4 to 6, to produce motile sperm unless he had precocious puberty. There used to be a term for them called “infant Hercules” and if one thinks the male sex drive is a minefield for a teenager, imagine have to deal with that as a preschooler (and his family and friends, too).
I’m sure Mother Nature and evolution care a lot less about the social implications of appropriate control of sex drive, and more (primarily) about the survivability of offspring. There’s the evidence that the children of early-teen girls tend to have more medical problems and there are more pregnancy complications. Similarly, the evolutionary path of human development seems to be that both parents hunt-and-gathered food for the child; and that humans evolved with a lot more of a blank slate than having a set of instinctive behaviours like some lesser animals. Everything from tool-making to hunting is learned behaviour, which children got by observing and being taught by the tribe. Evolution was not going to favour those who had children before they were able to provide for them.
(Much like the “grandmother effect”. Human females go through menopause, unlike many other mammals, since -theory says - it can take a decade or more before human offspring can fend for themselves, so popping out more kids when the mother might die in a year or two was not conducive to survival of the genes - whereas an additional older, experienced person with the time to help young mothers was always a beneficial complement to the tribe; much as it is today)