The farmers of Europe appear to be a very closely related group, that derives from a potentially singular source. We’ve seen several papers over the last couple years devoted to farmers. Last year brought us Lipson et al. (2017), and Mathieson et al. (2017). These papers brought us many new samples from the Mediterranean, Central Europe, and the Balkans. The datasets from these two papers will be the source that I am working with here.
Firstly, I wanted to look at a simple tree to find a decent fit. That led to the following:
This one was not a bad fit. It just had one zero drift edge towards Iron Gates, which would probably be taken care of if more hunters were included that lacked as much ANE as Iron Gates. While the Peloponnese samples are an outgroup to the other farmers, the Koros samples, from the First Temperate Neolithic, appear to be very close to the ancestral population for both the Balkan and Mediterranean groups. For the purpose of starting here, it seems fine. Next, I wanted to add Iberia EN as an offshoot of the Cardial EN samples from Croatia, just to see if the two of Mediterranean origin really are closely related.
This graph left what looks to be a needed admixture event from a hunter branch related to Iron Gates, to Iberia EN.
This graph actually turned out very nice. Iberia EN was able to branch from the same population as the Croatian Cardial and only needed a little extra HG ancestry. This also removed the zero edge from Iron Gates. For the next run, I am going to place LBK Austria coming off the branch to Starcevo.
The first thing I will try after seeing this worst Z-score is to try an admixture edge from the branch related to Iron_Gates into LBK Austria.
Surprisingly, the admixture from a European hunter did not take care of that worst Z-score. So, I scrapped that and decided to go with the admixture from Croatian Cardial into LBK Austria.
This graph resulted in LBK being a mix of 59% Starcevo and 41% Cardial. Still, we have a worst Z that wants Starcevo to also be closer to Cardial. In this case, I will first try a shared branch opposite of Koros, and if needed, after the HG-related admixture at B3.
While this is not a bad result, we do have a couple zero edges here that I would like to resolve. The admixture from the Cardial branch to LBK has also reduced to 5% in this graph. The worst Z involves the Peloponnese Neolithic and Starcevo, and also Iron Gates and LBK. I first want to try an edge from around Iron Gates to LBK to see how that does.
For this last graph, the A2 node for HG was eliminated since there was a 0 drift edge. All HG admixture now comes off of A1. The extra HG into LBK Austria has now put the worst Z-score around 3, which isn’t too bad. The edges all look good. The surprising part is that LBK comes out nearly 50% Cardial-related. This is interesting because, LBK was seen as just a subset of late Starcevo and potentially some Vinca influence. Since this is unexpected, I am going to see if there is more shared drift between the two before splitting, after the extra HG admixture coming after splitting with a group related to Koros EN.
Still, we have LBK Austria coming out as nearly half Cardial-related. While these results are interesting, they are not matching with D-stats, f3-ratio, or qpAdm results. There may be something else here that will take more complex graphs to figure out.
Here is another way of looking at it.
This graph makes a little more sense, with the separation of Mediterranean and Danubian groups a little more. The next step will be to separate the two before Koros EN. I will continue working from here for the rest of the post. If you have any more ideas, let me know. I will post updates as I have more.
Here are stats that have me thinking there is nothing here as far as admixture from Croatian Cardial.
Lipson, M. et al. Parallel palaeogenomic transects reveal complex genetic history of early European farmers. Nature 551, 368–372 (2017)
Mathieson, I. et al. The genomic history of Southeastern Europe. Nature 555, 197-208 (2018)