
Originally Posted by
IAlexN
What is it that causes every animal on Earth to want to mate and reproduce? Humans will feel attraction and love towards the person one would like to mate with, but most animals, and probably no insects do.
So, why do all living things want to reproduce?
The desire to reproduce has a genetic basis, driven by all manner of genes including the sex hormones. For example, in humans testosterone increases libido in both genders. Testosterone synthesis is controlled by several genes working together, so the efficiency, level etc of testosterone is inheritable. Any inherited trait that increases your chances of reproducing and/or surviving is obviously going to undergo positive selection, and will increase in the population over time, out competing less optimal varieties. Think about it this way- if you have 2 kids and one of them grows up to have low sex drive due to say, low testosterone production, which of your two kids is the more likely to produce more offspring? Move on to their kids, and the generation after and soon you find that kid A's progeny are being out competed by kid B's.