η εξέλιξη του σεξ

Part of being human involves planning for and having sex. It’s an important aspect of life—critical to the survival of our species.
Among homo sapiens, sexual activity is necessary for a variety of reasons, from procreation and the renewal of genetic traits to bonding between adults and just plain having fun.
However, sex was not always a part of the world. In the earliest days of life on planet Earth, creatures reproduced simply by breaking themselves in two.
In fact, asexual reproduction is still the way a great many organisms make more of themselves, through a process known as “mitosis.” Many single-celled plants and animals that are freely living today still reproduce just by splitting in half.
It’s fortunate for cavemen, and for us, that things have evolved from there. Apart from the dullness of mitosis, a species gains little from the effort. The same organism just keeps getting cloned repeatedly.
According to fossil records, sexual reproduction first appeared about 1,200 million years ago. One eukaryotic cell waggled its eyebrows at another and sex was born, giving rise to change and evolution.
But why?
Many researchers subscribe to the theory that sex became the dominant form of reproduction because genetic damage cannot be repaired asexually. Organisms need to replicate their genetic material in an efficient and reliable manner, and that’s what sex delivers.
The path to human sexuality was by no means a straight line, of course. A little confusion occurred along the way, such as with slugs, snails and earthworms, which are a bit of both sexes. But for the most part, a beneficent Nature sorted things out.
Lower animals just act on instinct and impulse when it comes to sex, but humans are different. From puberty onward (and in a good part of the population even before) sex keeps us interested, fascinated and engaged.
And sex is not just sex, either; it’s tied up with many other facets of human behavior and very hard to separate out of life at all. In cavemen times, it’s likely that attitudes to sex weren’t so much different from ours.
No doubt our Stone Age ancestors would have agreed wholeheartedly with Woody Allen, who has said, “Sex is the most fun you can have without laughing.”