grey_painter said:
Sexual reproduction was always described as a parasitic act by the male half of the species to me. The female produces all the nutrients in the egg and gestation period yet has to share half the genetic information with us males that produce nothing of any real value. Makes me feel really valuable.
That's kind of a half-truth. If it were purely parasitic, it wouldn't survive that easily. There are benefits to our survival that come from the mixing of genes.
There's often questions about some aspects of it though. In principle, it seems like it would make more sense for everyone to be hermaphrodites. (since this would allow anyone to reproduce with anyone else, which makes finding a partner much easier. In principle it even allows mating with yourself, as a last resort.)
But the usual explanation is that the two specialised groups tend to do better at their particular task than one that is capable of both.
The other common issue is why there is essentially a 50/50 split of male/female. This is especially obvious when you look at lions and similar 'harem' groups.
Think about it... A male's contribution to procreation lasts about 5 minutes to a few hours maybe (if you're lucky). A female's lasts
at least 9 months (in humans).
As a consequence, in the time it takes for a female to produce 1 child, a male can easily produce dozens, if not thousands.
Therefore, why aren't we in a situation where there is, say, 1 man to 100 women? Which would be perfectly practical from a reproductive perspective?
The answer seems to be genetics, because any gene that causes more males to be produced would be at an advantage when females outnumber males. This would in turn cause a gradual increase in the number of males around, until eventually you reach the point where it's no longer an advantage, which is the point where there's just as many males as females.
Look at lions. One male to 10 females is pretty common. And yet, the other 9 males still exist, even though they don't really serve any purpose in a setup like that.
OK... Enough scientific lecturing. XD.