Invention of weapons. New evolutionary arms race.
As early humans developed their material culture, they eventually invented somewhat effective wooden and stone weaponry around the time of Middle Paleolithic. The situation started to change.
First change was the place of human in nature. From a scavenger-gatherer, and an easy prey for large carnivores, he started to transform into a universal, multi-functional organism, with functions including being a predator. Once Mowgli acquired the Iron Tooth and the Red Flower, the tiger’s snack became the terror of the jungle. The rise in levels of safety and satiety was unprecedental. Birth rate has risen significantly. With weaponry, the human stopped balancing at the brink of extinction and started a global expansion, increased population size and area of habitat.
Second, any conflict for a place in the hierarchy or for a female could be an armed one. In an armed conflict, one of the males was killed, and the other maimed.
Third, a small group of people could leave the pack and still have a decent chance of survival. Essentially, human became a completely different, new species — but with old set of pack and herd instincts. Paleolithic was not long enough for the evolution to eradicate them, and it found other ways to solve the contradiction between the old instincts and the new conditions.
1. The most aggressive, strongest individuals were the first to perish in the internal conflicts, while those who could suppress the instincts for the time being, and use the mind instead, gained an advantage. A male within the top five by strength could, when in conflict with a stronger one, feign submission to avoid the fight and, during nighttime, kill the strong aggressive opponent with a stone in his sleep, and then take the place of the leader in the hierarchy. Or, he could kidnap a young female, run away and found a new group. In either case, his genes made it into the next generation. Genes of a man, whose mind defeated the instinctive through reason. Thus, low primativity was born. The ability of a human to act contrary to instinctive programs, to plan and to organize. To weaken, to replace the instinctive motivation of his behavior with rational motivation. This ability has improved learnability, as well as abstract thinking, which started the chain reaction. The human made its first step toward civilization, toward kingdom of the mind.
2. The qualities that made a group more competitive with wild nature became less important than the qualities that made a group more competitive with other groups. Here are the most important such qualities.
First, since the confilicts between the males for the females carried mortal danger, any single individual of either gender was a source of instability and risk in the group. The pack sexual market became very detrimental to the group. A group, which paired its members efficiently, got an advantage. Thus, monogamous marriage was born.
Second, those groups had an advantage in which individuals helped each other and worked as a team. That was useful in war, in hunt and in economic activity. Thus, biological moral and altruism were born — the qualities, opposite of selfishness as harmful for the group manifestations of hierarchical and self-preservation instinct of an individual. From the game theory standpoint, if stability of a pyramidal hierarchy is greater, the harsher the leader dominates, and with weaponry, the great equalizer, limiting the harshness, the only way to keep the hierarchy stable is to use negative quantities. Altruism is ambition with a negative sign. To put it simply, the group of people was kept together not only by fear, but by understanding, and by self sacrifice for the greater good. Our primeval ancestor gradually became less animal and more human. And that human behavior started to slowly make its way into the firmware — the instincts.
Gradually, a human pack transformed into a more modern form human society — a tribe. Every tribe was the more viable the more pack instincts were suppressed.
Again, there wasn’t enough time for the evolution to get rid of the herd instincts completely, they keep on conflicting, and working alongside with the new ones.
And finally, the most important. The unit of natural selection no longer an individuals (and genotype), but entire society as well. The new evolutionary arms race ran according to “whichever society can better neutralize the animalistic instincts has the advantage” rule. Since the females did not participate in the conflicts between groups, the biological moral, altruism and ability to suppress instincts evolved mostly in males. Females had no need to evolve anything new — the old animalistic selfish motivation still suited their biological purpose best.