Why does sex exist?

If you are thinking “for fun” then you and I think alike.  I raise a glass to you!

However, it’s a serious question.  If you do not know the answer to the question of why sex exists then essentially you do not know why male and females exist which means that you can’t know why you are woman or why you are a man.

Looking at the question from a more serious biological standpoint the answer is quite surprising.

In the last post, we already talked about the two primary instincts – survival and reproduction – so it must be one of those, right?

Yes it is one of those so pick one. Biologically, does sex exist for survival or reproduction?

If you ask most people why sex exists from a biological perspective they will almost always say it is for reproduction.  This is where it gets interesting.

Anybody who took even basic biology at school will know that there is such thing in nature as asexual reproduction.  That is to say, creatures who don’t need to have sex to reproduce.

Ok, human beings don’t do it but many frogs and worms do it.  Even large birds like turkeys can do it.  The female turkey will, when isolated from male turkeys, begin to produce eggs by herself that are already fertilised.  Many species can either reproduce asexually or can alternate between sexual and asexual reproduction as an adaption to their environment.

Now, bearing in mind that mother nature knows this neat little trick – how to get a species to reproduce without sex – and therefore proving that sex is not necessary at all for reproduction in nature, it begs a question.

If mother nature knows this neat little trick, why would nature evolve most creatures, including ourselves of course, into male and female sexually reproducing creatures?  Clearly it’s not necessary in nature for reproduction so why did nature do it?

There must be some survival advantage to it.

After all, sexual reproduction has many genetic survival disadvantages compared to asexual reproduction.

Unlike creatures that reproduce by cloning themselves, we have to go to all the trouble of not only going out to find a mate but we have to compete for them too, perhaps even to the death.

If you are picturing in your head nature documentary footage of peacocks going to all the effort of showing off their elaborate feathers and male deer clashing antlers and fighting to the death on the African savannah then you can imagine how easy the cloners life is.  A feet-up-in-front-of-the-TV and calmly enjoying their evening existence if ever there was one.

On top of that we might even contract a sexual transmitted disease as thanks for all our efforts.  Thanks nature !

No nasty sexually transmitted diseases for the cloners, no need for violent competition with other members of your same species and no need to ever leave the comfort of familiar and safe territory in the dangerous search of a mate across unknown terrain.

Wouldn’t it be better if human beings reproduced asexually?  Nightclubs across the world would be empty, churches would have to find something else to make people feel guilty about and blues and soul musicians all around the world would have nothing to write songs about.

However, the impact would not all be positive as we are about to find out.

The apparent genetic advantage of the cloners is always something that has always puzzled evolutionary biologists historically but a compelling theory has emerged which has been proven in lab conditions which I will share here as it may radically re-draw your map.

During asexual reproduction, animals essentially produce an exact genetic copy of themselves – a clone.  Makes sense bearing in mind that their own DNA is the only DNA that they have access to.

The female Turkey, as we mentioned earlier, when kept isolated from make Turkeys will produce fertilised eggs by herself but the chicks will not be as physically strong and are more likely to become ill and succumb to disease.

The answer to the question therefore rests with genetic diversity.

When sexual reproduction happens, 50% of the DNA of the father gets thrown away as does 50% of the DNA of the mother and the offspring gets the rest.

Except in cases of identical twins (or triplets etc.) they won’t get the same 50% each time which is why siblings of the same sex born to the same parents even 1 year apart don’t look exactly alike even though they share almost all the same genes.

In a cloned species however, they are genetic copies of each other.

Now what happens if we introduce a parasite into the environment of these clones?

Well if a parasite is successful at attacking and killing even one clone in that environment and the parasite spreads to other members of the species, how successful is it going to be?

Clearly a successful parasite that spreads in this environment can easily wipe out an entire species without ever having to change or to evolve to deal with different genetic signatures.

In sexually reproducing species however, this constant mixing and re-arranging of genetic signatures keeps the species a step ahead of parasites and makes it very difficult for any parasite to wipe out an entire species.

It is this constant DNA reshuffling that gives new born babies genetic signatures that are potentially better at dealing with parasites that their parents have lived with their entire lives and an advantage over the parasites in this evolutionary and biological arms race.

Therefore, sex exists in nature for reasons of survival – not reproduction.

This is something that has been theorised for some time but has since been proven in lab conditions.

So applying pure form theory to the question of “why sex exists?” we can answer that question in to just 2 words – parasite defence.  Or, if you prefer, just one word – biodiversity.

Gives you a new perspective when you a realise that the reason you are a woman or you are a man is due to the requirement for a parasite defence mechanism.

Both sexes existing in beautiful symbiosis.  Both helping to ensure the survival of one another and the of human race.

Seems that, if you really enjoy sex, you have a lot to thank those pesky parasites for.


  • The Black Knight

    JJ telling it like it is one more. Awesome post !

    So basically what you are saying is that sex is for survival whereas sexes are for reproduction, right?