The successful reproductive strategies of men and women are different. Men want to spread their genes by impregnating as many women as possible. Women want to have a man around to help protect and raise children, and they want the best possible man to impregnate them (for healthier children).
Mating for extended periods of child rearing is what enabled human beings to rise to the next level of advancement. Marriage was developed as the formal means for enforcing that mating constraint on men, who otherwise would be still trying to impregnate as many women as possible.
Marriage is a relatively recent invention. "Cheating" is a recent interpretation of otherwise natural instinct, layered over the biology which has been around for hundreds of thousands of years. Biology does not change quickly.
So, the reason men run around is obvious. As to why women run around.... they're usually looking to get themselves pregnant by a better man than the one they have (assuming they have one). Again, this is biology, and does not change quickly.
Here's the REAL kicker: Our modern welfare system has completely screwed up the natural instincts, by taking away the loyal male mate and replacing him with the government handout. It is a travesty.
What? Can you expound on that statement a bit? Relative to what, the age of the universe?
> Mating for extended periods of child rearing is what enabled human beings to rise to the next level of advancement.
One may view this (marriage, and the accompanying advancement as a species) as a gift from God. I do. It's the basis for the Seventh Commandment as well.
What failed were two things. First of all, for marriage to work as a better system of biology, it must be socially enforced. Those who violate the marriage, from the inside, or the outside, must be punished by society as a whole. If society stops enforcing marriage, it has to be self-policed, which is much less likely to work.
The other problem was that marriage was corrupted with the dowry, in an effort to turn a biological system into a business. Essentially prostituting women in biologically undesirable couplings so that her family will profit from selling her.
This was doubly bad, not only for the motive, but the means. This is because there is considerable speculation that prostitution, as such, fills a biological purpose as well.
For a given large group of men and women, there are a considerable number that for several reasons either should not, or cannot reproduce. Yet only some of them are “diverted” away from sexuality by being homosexual. The rest of the non-breeders thus interfere with those couples who should breed.
Prostitutes, often sterile or infertile, function well as such a diversion. It’s noteworthy that this may be such an important function, that even some postmenopausal women become hypersexual, to fulfill the role of prostitutes when there are not enough prostitutes.
And ironically, morality, in this case the opposition to prostitution, is also useful to keep males that should be breeding *away* from prostitutes.
So when a dowry is paid, a breeding female is sold to what usually is what should be a non-breeding male, often far older than the age of optimal fatherhood. As often as not this results both in poor quality offspring, and because the father dies soon after, insufficient, single parent upbringing of the child.
It is ironic that the rejection of this corruption overdid it, assuming that the perversion of dowry was a problem inherent in marriage itself. Which is why in modern times marriage has been so despised.
Around 10% of children are not from the person the mom said is the dad.
This is reflected in our biology.
If humans were more like the completely monogamous Gibbon - then we would have much smaller testicles.
If humans were like the much more promiscuous chimpanzee - we would have HUGE testicles.