Why Do We Have Sex ?
Having sex, where 2 adults come together and give rise to one offspring, is a pretty inefficient way to reproduce...
We could increase our numbers much faster if we could simply copy ourselves. Indeed, having sex is downright dangerous for some animals - just ask a male spider or a preying mantis - the female kills them after sex!
But sex is so widespread among both plants and animals that there must be an important evolutionary payoff.
So what is sex? Put bluntly, it enables us to mix our genes with those of our partner so that our offspring have half our genes, and half of our partner's genes, meaning that an infinite range of new genetic variations is possible, potentially enabling us to adapt to our surroundings more effectively.
So, for example, if I have a gene - call it A - that gives me an advantage in life, and you have a gene - call it B - that gives you a different advantage, the perfect combination would be a person with both A and B. So by mixing your genes with mine, we end up with the super person with both A and B.
The opposite is also true in that, if I have a bad gene that makes me susceptible to a certain disease, and I clone myself, then all of my offspring will also be susceptible to that disease. But by having sex and mixing my unhealthy genes with someone else's healthy genes ,I am minimising the chances of my children being affected by the disease.
So you see, there's more to sex than red roses and valentines day!