Thread by @palaeobeth

New #OpenAccess paper out today in @Nature! We present new #AncientDNA data on ancient African foragers (people who hunted, gathered, & fished), including what are now the oldest #aDNA sequences from sub-Saharan Africa! 1/21 🧵 nature.com/articles/s4158…

For an easily digestible summary of what we were looking for & what we found, check out our archaeologically-focused companion piece in @TheConversationUS by me, @archaeochica & @prendydigs theconversation.com/ancient-dna-he… 2/21

Paper itself is the product of a 5+ years work by 44 authors from 19 countries incl @prendydigs @archaeochica @kathrynranhorn @KendraSirak @johnwarthur @AyodoDr @BertacchiAlex @MatthewCCurtis @AGidna @KatongoMaggie @Myra__Laird @endiema @ogola_christine @WilloughbyPam @DJ_Kennett

We became interested in foragers once we realized herding/farming transformed African genetic landscapes. What did population structures look like before, & what can they tell us about what life was like in the Pleistocene? theconversation.com/ancient-dna-is… 4/21

There's evidence some big things were going down. ~50,000 years ago, we see a change in the archaeological record - the shift to the Later Stone Age. People began acting more 'modern' - tools, symbols, art that appeared in the Middle Stone Age became much more widespread... 5/21

New cultural traditions also started popping up - notably ostrich eggshell beads that hint at ancient social networks. See this great paper also in @Nature by @PalaeoJenn and @Yiming_V_Wang! nature.com/articles/s4158… 6/21

Why did this happen? A long-standing archaeological mystery! Some proposed an invisible genetic change made our brains more human. Others suggested that we were always had these abilities & what changed was the way we interacted with one another. But it’s been hard to test! 7/21

Hey, #aDNA would be a good way to test for demographic change around this time! But most aDNA from Africa is <5000 years old because hot/humid climates make DNA recovery HARD. So we targeted older sites with hopefully better preservation (mainly caves & rockshelters). 8/21

Success! We sequenced 6 new individuals who lived ~18,000-4000 years ago in what are now Tanzania, Zambia, & Malawi & analyzed them alongside 28 published individuals (generating higher coverage data for 15 of them). Now the largest #aDNA study of ancient African foragers! 9/21

What we found is that ALL the ancient foragers were descended from the same 3 lineages of eastern, southern & central African foragers. The only way to explain this is if people were moving widely in the Later Stone Age – when we see growing long distance exchange networks! 10/21

Based on when these lineages initially diverged, we know this happened after ~50,000 years ago – right around the same time as the Middle to Later Stone Age transition. 👀 👀 👀 11/21

Our study also tells us that by ~20,000 years ago, people had stopped moving & mixing as extensively. Ancient foragers in this study were most closely related to their neighbours, suggesting that people had begun to live more locally by the end of the Ice Ages. 12/21

This coincides with archaeological evidence for what we call regionalization, when Later Stone Age industries began to diversify. Maybe once long-distance networks were established, people didn’t need to move as much? Maybe there were other factors? 13/21

Why is this important? Research on the African past tends to focus on human origins or the last few thousand years (e.g., pyramids!) But the bits in the middle are equally important for understanding how human adapt to challenges & why our world looks like it does. 14/21

What's so amazing to me is that this ancient, complex population structure among African foragers was all but erased in the last few thousand years. We would have never known about it except for #aDNA – what else about the deep past are we missing? 15/21

It's also amazing what we can now learn from these people. I excavated one of the individuals in the study back in 2010. If you had told me then I would come back to study their DNA, I wouldn't have believed you! At the time, there was no #aDNA from Africa 16/21 (pic: @kbiittner)

Two of the other newly sequenced individuals were excavated in the 1950s (onlinelibrary.wiley.com/doi/full/10.10…) & 1970s & were kept safe in African museums for decades before we studied them. This study was only possible because of the archaeologists & curators who came before us. 17/21

Overall, this research makes us reconsider how static hunter-gatherers were toward the end of the Ice Ages, & how humans have always reorganized socially to deal with our challenges, past & present. This is about what makes us human. 18/21

For further reading, @prendydigs & I also wrote a fun @Nature Briefings piece about this article, which has consumed the vast majority of our lives for the past two years. Fun fact - I wrote this piece while I had covid 😷 😬nature.com/articles/d4158… 19/21

Shout out to @stonybrooku for doing a nice write up - news.stonybrook.edu/newsroom/new-g… I was a postdoc there when I started this project, thrilled to finally see this paper out! 🍾🎉 20/21

Also check out this great press write up by @RiceUniversity! Working on this paper has forever changed the way I do anthropology, & I could not be prouder to share our work with all of you! news.rice.edu/news/2022/anci… 21/21