Humans have evolved a disproportionately large brain as a result of sizing each other up in large cooperative social groups, researchers have proposed. A team led by computer scientists at Cardiff University suggest that the challenge of judging a person’s relative standing and deciding whether or not to cooperate with them has promoted the rapid expansion of human brain size over the last 2 million years. In a study, the team specifically found that evolution favours those who prefer to help out others who are at least as successful as themselves. The results of the study suggest that the evolution of cooperation, which is key to a prosperous society, is intrinsically linked to the idea of social comparison – constantly sizing each up and making decisions as to whether we want to help them or not. http://www.psypost.org/2016/08/large-human-brain-evolved-as-a-result-of-sizing-each-other-up-44354 Study: http://www.nature.com/articles/srep31459
Our closest relatives, the two species of chimpanzee, also use cooperation as a tool for improving their lives. The smaller bonobos, in particular, have huge sex orgies that include the children and the elders. The larger and better-known chimpanzees also cooperate, but they also exhibit behavior that is counter to cooperation. Two or three of them might gang up on another--especially a member of another pack--and kill him. By now you've probably guessed that bonobo packs are governed by a matriarchy, while males rule the packs of the larger and more familiar chimp species.
It's also linked to the ability to help them - not an easy thing to be able to do. The ability to help others, especially relative strangers or lots of different people, is a complex and hard-won ability.
