[Ortelio Teo Gibson]

Ortelio Teo Gibson  asked the Naked Scientists:
   
My son was born just a few weeks ago and it got me to thinking...Why are babies born with reproductive organs if they're not put to use until puberty???

I'd greatly appreciate an answer.
Thanks,

Teo
Nagaoka, Niigata, Japan

What do you think?

[smart]

Reproductive organs are essential for urination...

[alancalverd]

The characteristic of mammals is that all are born in pretty much the shape of adults. The same is true of birds, fish, and indeed almost everything except insects and parasites. So the naive answer is "because we are mammals, not insects". Mammals generally seem to reach sexual maturity at about one eighth to one tenth of their healthy life span, and humans aren't far off the mean.

[Kryptid]

Reproductive organs are essential for urination...

Not the gonads.

As to the OP, I'll give two possible reasons:

(1) It's easier to go ahead and develop those organs while the embryo is already in the process of developing other organs than it is to develop them "from scratch" when you reach puberty.

(2) It's a quirk of evolution that just happened to be kept because it worked.

[Bored chemist]

Because it's better to have them and not need them, than the other way round.

[Tomassci]

Devloping gonads in puberty can be risk. And energy insufficient.

[evan_au]

Some fish species change sex during their life, for example at a certain age, or if the senior member of that sex dies. In these species of fish, sexual organs at hatching is not necessarily the same as at death.

In humans, sex is determined by the X & Y chromosomes. So sex is effectively determined at time of fertilization. Sex determination starts to kick in at around 7 weeks, and sex is usually evident by 12 weeks.
- I understand that girls are born with a full set of eggs that she will have available as an adult. This could have the advantage of minimizing mutations between generations.
- Males use a very different strategy: they start producing sperm at puberty, and the progenitor stem cells keep dividing throughout life, which builds up more mutations as men get older.

See: https://en.wikipedia.org/wiki/Sexual_differentiation_in_humans#Sex_determination