Basal Eurasian discussion - Printable Version +- The GenArchivist Forum (https://genarchivist.com) +-- Forum: Human Population Genetics (https://genarchivist.com/forumdisplay.php?fid=21) +--- Forum: Ancient (aDNA) (https://genarchivist.com/forumdisplay.php?fid=181) +--- Thread: Basal Eurasian discussion (/showthread.php?tid=644) |
Basal Eurasian discussion - strawberry - 03-16-2024 In this thread we discuss Basal Eurasians. Summary for those who are unfamiliar with the topic: East Eurasians have higher Neanderthal ancestry than West Eurasians. Three hypotheses have been proposed to explain the difference: 1) Greater West Eurasian population size led to stronger purifying selection against Neanderthal ancestry. 2) East Eurasians received additional Neanderthal admixture after the initial admixture event between Main Eurasians and Neanderthals. 3) Neanderthal ancestry was diluted in West Eurasians by admixture from a hypothetical, deeply divergent "Basal Eurasian" ghost population with no Neanderthal ancestry. Basal Eurasians are theorized to have split from other Eurasians 60-100kya before Main Eurasians mixed with Neanderthals in the Near East. They may have lived somewhere in North Africa or the Near East, most likely the Arabian peninsula which aligns with proposed Out of Africa migration routes. Basal Eurasian ancestry varies by region in the ancient Near East: Caucasus_UP 24%, Anatolia_N 30%, Iran_N 45%, Natufian 50%. Ancient North African Iberomaurusians show high levels of Basal Eurasian ancestry and have been described as "the best ancient proxy for the basal Eurasian population group" (Ferreira 2021). Among modern West Eurasians, Basal Eurasian ancestry peaks among Arabians (40-45%), followed by Iranians (38%), Levantines (32%), Caucasians (20-25%), and is lowest among Europeans (<20%). Some people have proposed that Basal Eurasians did not exist and the simplest explanation is that ancient Near Easterners harbor additional admixture from Sub-Saharan Africans. However, Lazaridis 2016 found no evidence for SSA admixture in Natufians. Studies and figures: Ancient human genomes suggest three ancestral populations for present-day Europeans, Lazaridis 2014 Genomic insights into the origin of farming in the ancient Near East, Lazaridis 2016 Parallel paleogenomic transects reveal complex genetic history of early European farmers, Lipson 2017 Projecting Ancient Ancestry in Modern-Day Arabians and Iranians: A Key Role of the Past Exposed Arabo-Persian Gulf on Human Migrations, Ferreira 2021 Efficiently inferring the demographic history of many populations with allele count data, Kamm 2021 Population genomics of post-glacial western Eurasia, Allentoft 2024 RE: Basal Eurasian discussion - Woz - 03-17-2024 There is no such thing as "Basal Eurasian" as originally formulated. There's "Ancient North African", the component that represents about 40% of the ancestry of the Iberomaurusians and around 10-15% of the ancestry of the Natufians. It's clearly connected to haplogroup E, which split from haplogroup CF 63-69 kya, well before the estimated admixture with Neanderthals (50-60 kya). When those early researchers talked about certain Middle Eastern population being 40-50% "Basal Eurasian" what they really were looking at were population with 10% or so of this Ancient North African ancestry. It's probably either North African or SW Asian in origin. RE: Basal Eurasian discussion - kolompar - 03-17-2024 To me it feels like the idea of Basal was built on the assumption that the Out of Africa was Y-haplogroup CT and E is native to the Middle East and represents this basal population. Then we got the Iberomaurusians and it looks more like E is just a recent migration and the basal signal is mostly caused by just this Iberomaurusian admixture and the erronous models based on it. But the idea of Basal sticked around for some reason and everyone keeps choosing their own population to call Basal Eurasian (some have even chosen ANE, believe it or not ). If it's really from a population earlier than the main OoA wave, I don't see any evidence that there's such admixture in Eurasia apart from the Iberomaurusians. Shouldn't there be a simple f-stat that show it, without assumptions like Ust-Ishim is unadmixed OoA? We have all kinds of haplogroup A, B, E Africans. Or are they too mixed with earlier African populations or later West Eurasians? Or is Basal simply just the earliest split of the same OoA population, without Neanderthal? I'm not even sure about the lower Neanderthal part... Code: pop1 pop2 pop3 pop4 est se z p n RE: Basal Eurasian discussion - TanTin - 03-17-2024 Thanks everyone for starting this discussion and contributing to it. I have to admit that my idea of Basal was more or less different from the definition. Thank you Strawberry for the good explanation and details. My search for Basal was more oriented towards the ancient archaic form that contributed to OOA. But it's also very important to compare our understanding of the basic terminology and make sure we're using the same sense when trying to explain "Basal" or other abstract terms. Especially when we're talking about a hypothetical population. RE: Basal Eurasian discussion - TanTin - 03-17-2024 (03-17-2024, 09:09 PM)kolompar Wrote: To me it feels like the idea of Basal was built on the assumption that the Out of Africa was Y-haplogroup CT and E is native to the Middle East and represents this basal population. Then we got the Iberomaurusians and it looks more like E is just a recent migration and the basal signal is mostly caused by just this Iberomaurusian admixture and the erronous models based on it. These F4 are perfectly readable.. I am going to add some additional details by using the same example from your F4. So we use this example: f4( prefix, "Cameroon_SMA" , "Altai_Neanderthal.DG" , TEST, "Laos_Hoabinhian.SG" ) # "Cameroon_SMA" , "Altai_Neanderthal.DG" - are used as outgroups or reference line, where we compare other test populations to them. "Laos_Hoabinhian.SG" - is the reference individual or 0-line . We use it to compare the number of markers shared between test and other reference . If the test population have more markers in common with Cameroon_SMA - they will go in this direction. If TESt population has more markers in common with Altai_Neanderthal - they will be more related to Altay Neanderthal.. Below I will give you some visualization how this look like. RE: Basal Eurasian discussion - TanTin - 03-17-2024 For TEST population: let use all the individuals and populations in this list: > TEST [1] "Cameroon_SMA" "Altai_Neanderthal.DG" "Laos_Hoabinhian.SG" "Iran_GanjDareh_N" "Georgia_Satsurblia.SG" "Turkey_Epipaleolithic" [7] "Israel_Natufian_contam" "Morocco_Iberomaurusian" Then we run: f4( prefix, "Cameroon_SMA" , "Altai_Neanderthal.DG" , TEST, "Laos_Hoabinhian.SG" ) # # A tibble: 8 x 9 pop1 pop2 pop3 pop4 est se z p n <chr> <chr> <chr> <chr> <dbl> <dbl> <dbl> <dbl> <dbl> 1 Cameroon_SMA Altai_Neanderthal.DG Cameroon_SMA Laos_Hoabinhian.SG 0.0411 0.000793 51.9 0 809261 2 Cameroon_SMA Altai_Neanderthal.DG Altai_Neanderthal.DG Laos_Hoabinhian.SG -0.0588 0.00264 -22.3 3.40e-110 809261 3 Cameroon_SMA Altai_Neanderthal.DG Laos_Hoabinhian.SG Laos_Hoabinhian.SG 0 0 NaN NaN 809261 4 Cameroon_SMA Altai_Neanderthal.DG Iran_GanjDareh_N Laos_Hoabinhian.SG 0.000379 0.000267 1.42 1.56e- 1 783276 5 Cameroon_SMA Altai_Neanderthal.DG Georgia_Satsurblia.SG Laos_Hoabinhian.SG 0.000304 0.000299 1.02 3.09e- 1 679127 6 Cameroon_SMA Altai_Neanderthal.DG Turkey_Epipaleolithic Laos_Hoabinhian.SG -0.0000763 0.000480 -0.159 8.74e- 1 434127 7 Cameroon_SMA Altai_Neanderthal.DG Israel_Natufian_contam Laos_Hoabinhian.SG 0.000197 0.000433 0.455 6.49e- 1 323174 8 Cameroon_SMA Altai_Neanderthal.DG Morocco_Iberomaurusian Laos_Hoabinhian.SG 0.000436 0.000291 1.49 1.35e- 1 789545 Next, I will provide a better visualization. RE: Basal Eurasian discussion - TanTin - 03-18-2024 This is the graphic presentation. As you may see all the tested populations are very far from both Altai Neanderthal and Cameroon.. And they stay near the 0-line. However we may notice that Turkey is below the 0, so it has more from Altai. Other test groups are above 0, so they have more shared markers with Cameroon reference group. RE: Basal Eurasian discussion - TanTin - 03-18-2024 Now let exclude Altai and Cameroon, so we can see more details for the tested individuals. As we may see here in this example: Turkey are below the 0-line. So they have more shared markers with Altai Neanderthal, than Cameroon. All the rest are above 0-line. Laos is the 0-reference line. RE: Basal Eurasian discussion - TanTin - 03-18-2024 Quote:# A tibble: 10 x 9 With few more individuals from the list: RE: Basal Eurasian discussion - TanTin - 03-18-2024 The problem with these examples is that Z is below 3.. Many people will not accept this examples as statistically significant. The requirement is to have Z> 3. RE: Basal Eurasian discussion - TanTin - 03-18-2024 (03-17-2024, 09:09 PM)kolompar Wrote: To me it feels like the idea of Basal was built on the assumption that the Out of Africa was Y-haplogroup CT and E is native to the Middle East and represents this basal population. Then we got the Iberomaurusians and it looks more like E is just a recent migration and the basal signal is mostly caused by just this Iberomaurusian admixture and the erronous models based on it. Here is a full visualization for this data: RE: Basal Eurasian discussion - Kale - 03-18-2024 I was skeptical of Basal Eurasian for a while, and decided I would be convinced of it's existence if a sample was found meeting the following criteria. 1) Equally related to East-Eurasians, Paleolithic Europeans, and Ust-Ishim 2) Less related to all of the above than they are to each other 3) More related to hypothesized Basal Eurasian carrying populations ZlatyKun checks boxes 1 and 2, and gets partial credit on 3. She is not more related to ancient Near Easterners, but... ancient Near Easterners are equally related to her and Ust-Ishim, and that is despite the majority of their ancestry being derived from populations with significant preference for Ust-Ishim, meaning, the 'Basal' portion has to be more ZlatyKun related to counterbalance. What's going on with IBM is probably a separate phenomenon than BE. However, there is the matter that ZlatyKun is more related to Ust-Ishim than Iran_N are, meaning Iran_N is more 'Basal'. There are 2 simple ways of resolving that. Either 1) ZK = BE + some undifferentiated 'crown Eurasian', or 2) Iran_N has ZK-like BE, plus something even more Basal (which could be IBM-related). RE: Basal Eurasian discussion - Norfern-Ostrobothnian - 03-18-2024 Considering that neither Iran Neolithic, CHG nor Anatolian have any affinity to Iberomaurusian beyond their Anatolian ancestry I think they actually have some component that cannot be associated with East or West Eurasians. RE: Basal Eurasian discussion - Kale - 03-18-2024 In regards to the qpgraph model in the OP, it frustrates me to no end that authors do not conduct basic sanity checks when performing these. The 36 unit drift edge leading to Iran_N (~twice their OOA bottleneck!) is bogus, Iran_N are the least bottlenecked population in West Eurasia at that time. To correct that issue would change the whole structure of the graph. RE: Basal Eurasian discussion - Woz - 03-18-2024 The affinity for Zlaty Kun in Iranian HG's is likely from their Baradostian ancestry, which we don't have samples of, and which is not Zlaty Kun, just some early branch of Eurasians. Perhaps this is what those early researchers called "Basal Eurasian": a mixture of Baradostian (admixture calculators go for Zlaty Kun as a proxy in the absence of actual Baradostian samples) and "ANA" (quite possibly Emiran). Zlaty Kun had Neanderthal ancestry though, and probably so did Baradostian. |