This is a short post here, before moving onto a larger one with something I find interesting regarding potential flow from Iberomaurusian to European farmers, maybe via the Capsian culture. I will save anymore on this for that specific post.
I wanted to try a little something that we see often in papers of the couple years, where Mota is used as a stand-in for an ancestral branch called “Basal Eurasian” in modeling on qpAdm. I don’t recall seeing this in any papers, so I thought that I would give it a try. These are three simple trees, the first involves Chimp, Mota, Ust_Ishim, IBM (Iberomaurusians), Anatolia_HG (Pinarbasi), Kostenki14, Tianyuan, and Natufians. Theses samples come from Lazaridis et al (2016), van de Loosdrecht et al (2018), and Feldman et al (2019).
Technically, I didn’t intend to use a Basal branch, and thought that if anything was needed between Mota and Ust_Ishim, the worst Z-score would require something away from Mota’s branch and diverging instead on the one towards Ust_Ishim, which I should expect if my interpretation of the tree is correct. While I do not want to speculate on Mota’s specific place in tree between “African” and “Eurasian”, nor his potential non-“African” ancestry (I have serious doubts about being able to decipher that after looking at IBM and also potential artifacts with regard to stats involving African samples), I wanted to focus more on seeing if direct ancestry from a related source does work. The results were interesting and did work, just as they do in qpAdm.
While running this, I was curious to see if I could avoid the Z-score between Natufians and IBM with a direct contribution from Mota. This still left a very significant Z-score, showing that direct contribution from a source related to Iberomaurusians was going to be the only way forward.
This was pretty close to the input from both IBM and Dzudzuana, from Lazaridis et al (2018). I eagerly await that sample, to see this a little more. I also wondered about the low Mota to Anatolia edge; thinking it has something to do with what I believe is Kostenki14 already possessing some Dzudzuana-related ancestry, compared to GoyetQ116-1. For the time being, I chose to keep that for later and focus on building this tree.
The next thing I wanted to do was to see how Ganj_Dareh_N fit into all this and if anything beyond Anatolia, Natufians or IBM, and Tianyuan was necessary. To a bit of my surprise, input from Iberomaurusians was quite low, and an extra edge from Mota was needed. Could there be another expansion via a southern route to the Persian Gulf? Potentially, or having more samples near the time of Dzudzuana would show a more deeply branched group in the region. Many things are possible here. While that extra input is small, the Z-score warranted the extra branch to keep that Z-score as low as it is.
The next thing I wanted to check on was how this would change with GoyetQ116-1 being inserted for Kostenki14. I think the results are a confirmation of sorts for some introgression from a Dzudzuana-related pop into all UP Europeans, except for GoyetQ116-1. Meaning that Mota-related input does increase across the board.
These results are pretty interesting and show that using a branch that splits from a line to Mota does work as a source of deeper ancestry in West Eurasians. The potential artifact with African samples, along with more samples being needed to see the formation of the population Mota comes from are definitely needed to see if the same branching can hold, or if Mota is admixed with some type of Eurasian himself. Maybe Mota is mostly derived from a branch that separated from “Bssal Eurasian” well before admixing into the Near East and North Africa. The interesting thing is that even without Dzudzuana, the results still show Iran needing more input from the deep branch of ancestry and also sizeable ENA input. This is an interesting and exciting time. Hopefully, we will get more samples from Africa and West Asia throughout the Late Pleistocene to see what was going on there.
Sources
Feldman et al (2019) Late Pleistocene human genome suggests a local origin for the first farmers of Anatolia. https://www.nature.com/articles/s41467-019-09209-7#Sec20
Lazaridis et al (2016) Genomic insights into the origin of farming in the ancient Near East. https://www.nature.com/articles/nature19310
Lazaridis et al (2018) Paleolithic DNA from the Caucasus reveals core of West Eurasian ancestry. https://www.biorxiv.org/content/10.1101/423079v1
van de Loosdrecht et al (2018) Pleistocene North African genomes link Near Eastern and sub-Saharan African human populations. http://science.sciencemag.org/content/360/6388/548
Population Genomics 
Couple of interesting things I’m seeing with Tianyuan in these graphs. In the first one, Tianyuan is basal to Ust Ishm, and in the second and third he contributes nearly half the ancestry of Ganj_Dareh. I don’t think I’ve ever seen models of Iran Neo being this East Eurasian. I think on most PCAs I’ve seen that incorporate both ancient and modern samples, Iran Neo basically plots with contemporary Iranian people, you wouldn’t think he has an overabundance of East Eurasian ancestry. Which I guess leads me to my next question, just how accurate are PCAs that mix ancient and modern populations together? Do they all suffer from some sort of projection bias which artificially shrinks the distance between ancient populations and their modern descendants?
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