A note on the Sunghir DNA results from an Australian perspective

ANCIENT NETWORKERS  DNA from four Stone Age people — including the two shown here as they looked when excavated, top, and at the time of death, bottom — suggests that hunter-gatherers have long formed groups with few close relatives. Aside from discouraging inbreeding, that social structure encouraged cooperative ties among groups and rapid cultural advances, scientists say. 

Interesting piece in Science News by Bruce Bower, Ancient humans avoided inbreeding by networking (5 October 2017) on the results of DNA analysis of four individuals from the Sunghir site in Russia, Sunghir is situated about two hundred kilometres east of Moscow, on the outskirts of Vladimir, near the Klyazma River.

The story is based on an article that appeared in Science. If you follow the link through you can access the original article, You will need to register, but that is free. The article's abstract reads:  

Present-day hunter-gatherers (HGs) live in multilevel social groups essential to sustain a population structure characterized by limited levels of within-band relatedness and inbreeding. When these wider social networks evolved among HGs is unknown. Here, we investigate whether the contemporary HG strategy was already present in the Upper Paleolithic (UP), using complete genome sequences from Sunghir, a site dated to ~34 thousand years BP (kya) containing multiple anatomically modern human (AMH) individuals. We demonstrate that individuals at Sunghir derive from a population of small effective size, with limited kinship and levels of inbreeding similar to HG populations. Our findings suggest that UP social organization was similar to that of living HGs, with limited relatedness within residential groups embedded in a larger mating network.

Martin Sikora1, Andaine Seguin-Orlando, Vitor C. Sousa, Anders Albrechtsen, Thorfinn Korneliussen, Amy Ko, Simon Rasmussen, Isabelle Dupanloup, Philip R. Nigst, Marjolein D. Bosch, Gabriel Renaud, Morten E. Allentoft, Ashot Margaryan, Sergey V. Vasilyev, Elizaveta V. Veselovskaya, Svetlana B. Borutskaya, Thibaut Deviese, Dan Comeskey, Tom Higham, Andrea Manica, Robert Foley, David J. Meltzer, Rasmus Nielsen, Laurent Excoffier, Marta Mirazon Lahr, Ludovic Orlando, Eske Willerslev, "Ancient genomes show social and reproductive behavior of early Upper Paleolithic foragers", Science 05 Oct 2017. eaao1807, DOI: 10.1126/science.aao1807

Bruce's report focuses on what the results might show us about mating patterns among hunter gatherers (HG). I looked at the results from a slightly different perspective. First to summarise some key points as I understood them:

• The DNA of four individuals was analysed. The remains dated from around 34,000 years ago.
• The DNA of the three individuals buried together share both mitochondrial and Y-chromosome lineages  That is, they formed part of the same group. However, none of them were closely related (that is, third degree or closer). Third degree relationships includes first cousins, great grandparents and great grandchildren. 
• Modelling provided a refined estimate of the time since admixture with Nenaderthals at 770 generations (95% CI 755-786). Accounting for the uncertainty of both the admixture estimate and 14C ages, this corresponds to an admixture date between the ancestors of Sunghir and Neanderthals of between 53.6 and 58.1 kya (at 29 years/generation. However, the results from one individual suggested that there could have been a more recent admixture.

.The Aborigines arrived in Australia perhaps 60-65,000 years ago. That is before the estimated admixture date between the Sunghir and Neanderthals. They too carry Neanderthal genes, although they also carry Denisovan genes, suggesting a later mixing with Denisovan peoples. So the evidence continues to suggest that we are dealing with long and overlapping periods of interaction between different hominin species.

 I am not quite sure what conclusions to draw from the DNA results so far as breeding patterns within the Sunghir group are concerned. However, it would not be surprising if they had kinship arrangements designed to prevent in-breeding.. Aboriginal kinship arrangements have that effect while also fitting people into social structures. Those arrangements probably evolved with time. We cannot assume that those holding among Aboriginal people at the time of European occupation were the same as those holding 65,000 years before.

Too a degree, too, this type of arrangement depends upon population size. In-breeding is more common among smaller groups.