Humans are able to build knowledge that is passed through generations. This could be a feature unique to humans. At what point this distinctive pattern emerged, however, is not clear.
Human cultures, including our technologies, artifacts and traits, have progressed over time, becoming more sophisticated, complex and efficient as generations pass. This cumulative process, often described as the “ratchet effect”, specifically encapsulates how high-fidelity social learning maintains our cultural accomplishments until such a time as new, bene- ficial modifications are invented, which in turn are propagated via high fidelity social learning [@vale2012Cumulative culture and future thinking: Is mental time travel a prerequisite to cumulative cultural evolution?]
For earlier groups of humans, egalitarian societies explain diveristy in hunter-gatherer groups, which could further increase the accumulation of knowledge and cooperation among people.
The shift from an acnestral hierarchical, female-dispersal sstem to a multilocal, egalitarian one would provide the selective context for expanded social networks, cumulative culture, and cooperation among unrelated individuals. [@dyble2015Sex equality can explain the unique social structure of hunter-gatherer bands]
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