Do you know your neighbours? If not you might be at an evolutionary disadvantage. It turns out socialising with those around us is a key part of our evolutionary success. In fact, we may have evolved big brains to maintain these relationships.
Or at least, that's the theory. The thing is the Neanderthals weren't quite so neighbourly. Despite living in close proximity to each other, there's little evidence of Neanderthal groups being chums. In fact, they remained so isolated inbreeding became a problem.
So have we been exaggerating how social prehistoric people were? Or were the Neanderthals just unusually introverted? Fortunately, ancient DNA is helping shed light on this. An ancient group from shortly after the isolated Neanderthals has kindly donated their DNA. It finally reveals whether prehistoric people were good neighbours.
Sungir DNA
The ancient DNA in question comes from fossils that are already famous; albeit for a different reason. They had a really jazzy hat.
The group in question hails from a site called Sungir, in Russia. At least 6 people were buried there (including 2 kids in a shared burial) around 33,000 years ago. For context, that's around the time Neanderthals were going extinct in the region. And of course, they're famous for their awesome clothes.
For instance, the two kids in a shared burial had thousands of beads stitched into their clothes. As well as shedding light on how Palaeolithic people dressed, you've also got to marvel at the effort involved. Between all of these burials, there are at least 13,000 man hours invested in the production of all these beads. And if that wasn't fancy enough, they've also got massive mammoth ivory spears, carefully straightened to make weapons 2 metres long.
As an interesting aside, the quantity and quality of these grave goods have raised many questions. Namely, how did kids get them? They wouldn't have had the time to acquire them during life. Perhaps they inherited them, hinting at the first examples of proper possession in (pre)history. Or it could be a ritual.
Asides aside, these are the graves we're dealing with. Researchers were able to get DNA out of all but one of these individuals. This allowed them to compare how much inbreeding was going on. Where they really living isolated lives like the Neanderthals around them? Or were the Neanderthals the odd ones out of human evolution.
Good neighbours, good mates
I shan't keep you in suspense any longer. It turns out that the Sungir group was doing a lot less inbreeding than Neanderthals. This mirrors the pattern seen in modern hunter-gatherer groups. Because they're friendly with their neighbours, mature individuals often move between groups. This means only 10% of the average hunter-gatherer group is a close relative, keeping inbreeding to a minimum.
As well mating with other modern humans, this group was also interbreeding with the Neanderthals. The Sungir group split from other Europeans around 5,000 years earlier. During that time of (relative) isolation they seem to have mated with local Neanderthals, resulting in a few fractions of a percent extra Neanderthal DNA entering their group, compared to other Europeans.
All of this seems to show that prehistoric humans were good neighbours, interacting often with the groups around them (even if they weren't the same species). Of course, this is just one group. Maybe they were the extroverts of the stone age. As more data comes in we can hopefully get a clearer picture of how much ancient humans interacted, but early results suggest the answer was: a lot.
Because as we all know from game of thrones, the inbreeding alternative is a bad one.
References
d'Errico, F. and Vanhaeren, M., 2015. Upper Palaeolithic Mortuary Practices: Reflection of Ethnic Affiliation, Social Complexity, and Cultural Turnover. Death Rituals and Social Order in the Ancient World: Death Shall Have No Dominion, p.45.
Sikora, M., Seguin-Orlando, A., Sousa, V.C., Albrechtsen, A., Korneliussen, T., Ko, A., Rasmussen, S., Dupanloup, I., Nigst, P.R., Bosch, M.D. and Renaud, G., 2017. Ancient genomes show social and reproductive behavior of early Upper Paleolithic foragers. Science, p.eaao1807.
