Originally Posted by
Caerule
Humans have been effective, because of the social tendencies imprinted in our genes. Raising children in partnerships. Working in cooperative groups. Even our empathic capabilities reaching beyond our species, to allow for domestication of animals. These things have allowed us to more effectively obtain average wealth per individual, and ensure the survival of our genetic code. A tribe that has both parents loyally raise children has more genetic diversity, and higher child survival rate, than a system of non-monogamy. Halting incest also increases genetic variety. Cooperation lets individuals specialize in roles, and succeed at larger tasks together. Not murdering each other, even when paths don't align, leads to a greater variety in genes and perspectives.
Being a dick can work. It certainly works for the great apes for a degree, where harem structures can exist. Like Gorillas. But that's not the path that won out for humans. Those that did better than the others, were those whose genes were selected into our current morality. And part of that is that there's social consequences to being a dick, and going against the morality.
It's laid the foundation for a system of expanding social evolution, where more elaborate systems of morality are constructed upon. As elaborate as our current system of laws and social norms. And of course, a lot of variation exists. But it's only maintained because the majority has the foundation for the current system we have.
You have to remember that "Fitness" doesn't just depend on how well of a life you carve out for yourself. It can help. You're not going to pass on your genes if you can't prosper. But you also need to be selected as a partner, invest in your children's fitness, and make use of a system of cooperation, in order to be part of a successful lineage.
Basically, a collective/tribe with few self-centered douches performs better than one full of douches. The tribe that prospers, shapes the future of the species.