The rise of agriculture may have been influenced by the downfall of equality among the sexes. The genders had enjoyed parity up until that point, according to researchers from the University College London.
After studying group dynamics of prehistoric foragers, the researchers determined that our ancestors' bands were too diverse to have been joined together on the say-so of men alone.
"Sex equality suggests a scenario where unique human traits such as cooperation with unrelated individuals could have emerged in our evolutionary past," said senior study author Andrea Migliano.
Women had an equal say in cohabitation, otherwise the guys would have hung out with their relatives and kept their wives around the fringes of the group, according lead study author and anthropologist Mark Dyble.
"If men and women decide, you don't get groups of four or five brothers living together," said Dyble in an interview with the Guardian.
Previous research has noted the diversity and low relatedness in hunter-gatherer groups, but the University College London study has presented an explanation, said Dyble.
"It is not that individuals are not interested in living with kin," said Dyble. "Rather, if all individuals seek to live with as many kin as possible, no one ends up living with many kin at all."
The researchers lived among hunter-gatherer groups in the Philippines and Congo and interviewed hundreds of people to piece together the participants' family trees.
The scientists learned that many of the study's participants were cohabiting with a large number of unrelated people, despite living in small groups and sparsely populated areas.
In a computer model constructed from the data they collected, the scientists saw that relatedness inside the simulated camp was high. When both sexes had a say in cohabitation, families would visit groups composed of the wife's relatives at times and then spend time checking in on camps made up of the husband's relatives.
"There is still this wider perception that hunter-gatherers are more macho or male-dominated," said Dyble. "We'd argue it was only with the emergence of agriculture, when people could start to accumulate resources, that inequality emerged."
The results of the study impressed Tamas David-Barrett, a behavioral scientist at the University of Oxford.
"If you're able to track your kin further away, you'd be able to have a much broader network," said David-Barrett. "All you'd need to do is get together every now and then for some kind of feast."
