E. O. Wilson argues that the single most important factor that leads to the success of ant colonies is the existence of a sterile worker caste.
The existence of sterile castes among these social insects significantly restricts the competition for mating and in the process fosters cooperation within a colony.
Highly social mammals such as primates and elephants have been known to exhibit traits that were once thought to be uniquely human, like empathy and altruism.
These traits include high intelligence, a capacity for symbolic communication, a sense of social norms, realization of "self", and a concept of continuity.
[5][6] Frans de Waal and Barbara King both view human morality as having grown out of primate sociality.
Many social animals such as primates, dolphins, and whales have shown to exhibit what Michael Shermer refers to as premoral sentiments.
[10] Animals such as Capuchin monkeys[11] and dogs[12] also display an understanding of fairness, refusing to co-operate when presented unequal rewards for the same behaviors.
Based on the size of extant hunter gatherer societies, recent paleolithic hominids lived in bands of a few hundred individuals.
This numerical limit is theorized to be hard coded in our genes since even modern humans have difficulty maintaining stable social relationships with more than 100–200 people.
The brain allows an individual to recognize patterns, perceive speech, develop strategies to circumvent ecologically-based problems such as foraging for food, and also permits the phenomenon of color vision.
Within populations of social animals, altruism, or acts of behavior that are disadvantageous to one individual while benefiting other group members, has evolved.
This notion seems to be contradictory to evolutionary thought, because an organism's fitness and success is defined by its ability to pass genes on to the next generation.
According to E. Fehr, in the article, The Nature of Human Altruism, the evolution of altruism can be accounted for when kin selection and inclusive fitness are taken into account; meaning reproductive success is not just dependent on the number of offspring an individual produces, but also the number of offspring that related individuals produce.
[20] Outside of familial relationships altruism is also seen, but in a different manner typically defined by the prisoner's dilemma, theorized by John Nash.
The prisoner's dilemma serves to define cooperation and defecting with and against individuals driven by incentive, or in Nash's proposed case, years in jail.
Brune details that theory of mind has been traced back to primates, but it is not observed to the extent that it is in the modern human.
Failure to understand another's intentions and emotions can yield inappropriate social responses and are often associated with human mental conditions such as autism, schizophrenia, bipolar disorder, some forms of dementia, and psychopathy.
[19] The need for social intelligence surrounding theory of mind is a possible answer to the question as to why morality has evolved as a part of human behavior.
By including ever watchful ancestors, spirits and gods in the social realm, humans discovered an effective strategy for restraining selfishness and building more cooperative groups.