Prehistoric Humans are Likely to Have Formed Sex Networks to Avoid Inbreeding
The people at Sunghir may have been part of a network similar to that of modern day hunter-gatherers, such as Aboriginal Australians and some historical Native American societies. Like their Upper Paleolithic ancestors, these people live in fairly small groups of around 25 people, but they are also less directly connected to a larger community of perhaps 200 people, within which there are rules governing with whom individuals can form partnerships.
"Most non-human primate societies are organized around single-sex kin where one of the sexes remains resident and the other migrates to another group, minimizing inbreeding" says Professor Marta Mirazón Lahr, from the Leverhulme Centre for Human Evolutionary Studies at the University of Cambridge. "At some point, early human societies changed their mating system into one in which a large number of the individuals that form small hunter-gatherer units are non-kin. The results from Sunghir show that Upper Paleolithic human groups could use sophisticated cultural systems to sustain very small group sizes by embedding them in a wide social network of other groups."
By comparison, genomic sequencing of a Neanderthal individual from the Altai Mountains who lived around 50,000 years ago indicates that inbreeding was not avoided. This leads the researchers to speculate that an early, systematic approach to preventing inbreeding may have helped anatomically modern humans to thrive, compared with other hominins.
This should be treated with caution, however: "We don't know why the Altai Neanderthal groups were inbred," Sikora said. "Maybe they were isolated and that was the only option; or maybe they really did fail to develop an available network of connections. We will need more genomic data of diverse Neanderthal populations to be sure."
Willerslev also highlights a possible link with the unusual sophistication of the ornaments and cultural objects found at Sunghir. Group-specific cultural expressions may have been used to establish distinctions between bands of early humans, providing a means of identifying who to mate with and who to avoid as partners.
"The ornamentation is incredible and there is no evidence of anything like that with Neanderthals and other archaic humans," Willerslev added. "When you put the evidence together, it seems to be speaking to us about the really big questions; what made these people who they were as a species, and who we are as a result."
Top image: Model of two ancient humans. Credit: Genetic Literacy Project
The article ‘Ancient Denisovan DNA excavated in modern Pacific Islanders’ was originally published on Science Daily. Source: St John's College, University of Cambridge. " Prehistoric humans are likely to have formed mating networks to avoid inbreeding ." ScienceDaily. ScienceDaily, 5 October 2017. www.sciencedaily.com/releases/2017/10/171005141759.htm