Oh, and another thing.

Another thing I have to mention that I think is important is that "survival of the species" does not mean have a many children as possible. Every species has a best average number of children per parent that is different.

I don't know what it is for humans, but let's assume it is 2.2 children per parent. This can be acheived in many ways:

a) all humans are heteros and heteros have an average of 2.2 children per parent.

b) 50% of humans are heteros, and heteros have an average of 4.4 children per parent.

c) 10% of humans are heteros, and heteros have an average of 22 children per parent.

So you see, in option c) you have 90% of humans that aren't attracted to adult opposite sex type humans, and yet you still get the exact same effect as to the survival of the species, because the average number of children per parent (in total) is still 2.2.

So basically, the percentage of humans that are heteros, or childlovers, or gay, or animallovers, or shoelovers, or computerlovers hardly affects the survival of the species at all. As far as evolution is concerned, it's an arbitrary number and we might as well be 99% childlovers for all that evolution cares.

It's just plain bad luck that childlovers happen to be a small number. That's all.