Angela
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There can’t be any rational discussion of the issues raised by Brotherton et al, or any advancement in our knowledge of this period when statements are made concerning it that are totally at odds with a plain reading of the text.
Once again, this is what they say in the abstract: Our results reveal that the current diversity and distribution of haplogroup H were largely established by the Mid Neolithic (~4000 BC), but with substantial genetic contributions from subsequent pan-European cultures such as the Bell Beakers expanding out of Iberia in the Late Neolithic (~2800 BC).
They are thus claiming that already by 4,000 BC, the major part of the current diversity and distribution of H had already been established, and that therefore Bell Beaker, and Corded Ware, and Unetice) did not create the general pattern of diversity and distribution of mtDNA “H” we see in modern populations. It was already in place, or so they claim.
In the body of the paper they then go on to state this, “The combined set of analyses (PCA, Procrustes and Ward clustering) revealed that Mittelelbe-Saale’s earliest farmers (LBK; n=9) cluster with present-day Caucasus, Near Eastern, and Anatolian populations, as previously noted7. In contrast, individuals from the successor series of regional post-LBK (and Mid Neolithic) Rössen, Schöningen, Baalberge, and Salzmünde cultures (ca. 4625-3025 BC, MNE; n=10) cluster with present-day Central European populations (Figure 2
They further state that ,” ENE (Early Neolithic) mt genomes are generally either rare today19 or have not yet been observed in present-day populations, possibly due to subsequent extinction of these lineages” and that “This suggests that individuals from the Early Neolithic made a marginal contribution to Late Neolithic and present day hg H diversity. Although the relatively small sample numbers from each time period limit detailed analyses of the causes of the distribution shifts, we interpret this phylogenetic pattern as a genetic discontinuity between Early and subsequent Neolithic cultures in Europe, potentially mirroring genetic structure in Neolithic European populations.”
Now, such a change could be caused by either migrations or drift. The authors specifically state that drift was not the cause:
“Genetic drift could also have played a role in generating discrepant hg distributions over time and space. However, if drift was the sole cause we would expect a random distribution across all sub-hgs rather than a clear distinction between ENE and MNE/LNE/Bronze Age mt genomes.”
That leaves migration of peoples bearing other subclades of “H” as the explanation, but they never state that explicitly and so they obviously don’t explain where and when these people arrived in the area. Now, I personally have no problem speculating that there was continuous gene flow during the Neolithic or perhaps a few pulses of gene flow which would bring diversity to the area. I do have a problem with an analysis that leaves that as the only explanation but doesn’t explicitly address the issue. Nor, for that matter, do I think their argument against drift as an explanation is all that convincing. If the sample sizes are too small from each period to figure out how the diversity developed, then why aren't they too small to so definitively rule out drift as one of the factors.
Apologies to Aberdeen for speaking for him, but it seems to me that this must be the same logical trail he followed, a trail which led him to conclude that, “Here's an article published by Nature Communications about a study that suggests Europe's modern mtDNA signature was largely established about 6000 years ago, in the mid Neolithic, by people of an unknown origin who largely replaced the early Neolithic farmers, for reasons that aren't yet clear.”
The authors are clearly proposing that some genetic transition did indeed take place between the LBK or early Neolithic and the mid-Neolithic cultures before the arrival of Bell Beaker, Corded Ware, or Unetice. Now, this may not be supported by the data, it may indeed not be the best explanation of what actually happened in Europe, but it is unambiguously what they did say.
They are most definitely not saying that “ Europe's modern mtDNA signature was largely established about 6000 years ago as a result of migrations into Europe during the early Neolithic" to quote a post by Polako. Given the text of the main paper quoted above, it's also incorrect to maintain that the authors propose that “The descendants of early Neolithic farmers weren't replaced about 6000 years ago but were the ones who largely established Europe's modern mtDNA gene pool at this time." Clearly they are saying that there were indeed changes between the arrival of the first farmers and the Middle Neolithic of 6000 years ago. (4000 BC)
One can disagree with the conclusions of Brotherton et al, but one can’t re-write them; that just leads to frustration, confusion among readers, and further bad conclusions.
In addition to all of the above problems with this paper, I agree with Aberdeen that the authors are making a huge error in taking results from one area in Germany, and very small sample sizes for each specific time period, and presuming to then extrapolate from that to make broad generalizations about the peopling of Europe.
Once again, this is what they say in the abstract: Our results reveal that the current diversity and distribution of haplogroup H were largely established by the Mid Neolithic (~4000 BC), but with substantial genetic contributions from subsequent pan-European cultures such as the Bell Beakers expanding out of Iberia in the Late Neolithic (~2800 BC).
They are thus claiming that already by 4,000 BC, the major part of the current diversity and distribution of H had already been established, and that therefore Bell Beaker, and Corded Ware, and Unetice) did not create the general pattern of diversity and distribution of mtDNA “H” we see in modern populations. It was already in place, or so they claim.
In the body of the paper they then go on to state this, “The combined set of analyses (PCA, Procrustes and Ward clustering) revealed that Mittelelbe-Saale’s earliest farmers (LBK; n=9) cluster with present-day Caucasus, Near Eastern, and Anatolian populations, as previously noted7. In contrast, individuals from the successor series of regional post-LBK (and Mid Neolithic) Rössen, Schöningen, Baalberge, and Salzmünde cultures (ca. 4625-3025 BC, MNE; n=10) cluster with present-day Central European populations (Figure 2
They further state that ,” ENE (Early Neolithic) mt genomes are generally either rare today19 or have not yet been observed in present-day populations, possibly due to subsequent extinction of these lineages” and that “This suggests that individuals from the Early Neolithic made a marginal contribution to Late Neolithic and present day hg H diversity. Although the relatively small sample numbers from each time period limit detailed analyses of the causes of the distribution shifts, we interpret this phylogenetic pattern as a genetic discontinuity between Early and subsequent Neolithic cultures in Europe, potentially mirroring genetic structure in Neolithic European populations.”
Now, such a change could be caused by either migrations or drift. The authors specifically state that drift was not the cause:
“Genetic drift could also have played a role in generating discrepant hg distributions over time and space. However, if drift was the sole cause we would expect a random distribution across all sub-hgs rather than a clear distinction between ENE and MNE/LNE/Bronze Age mt genomes.”
That leaves migration of peoples bearing other subclades of “H” as the explanation, but they never state that explicitly and so they obviously don’t explain where and when these people arrived in the area. Now, I personally have no problem speculating that there was continuous gene flow during the Neolithic or perhaps a few pulses of gene flow which would bring diversity to the area. I do have a problem with an analysis that leaves that as the only explanation but doesn’t explicitly address the issue. Nor, for that matter, do I think their argument against drift as an explanation is all that convincing. If the sample sizes are too small from each period to figure out how the diversity developed, then why aren't they too small to so definitively rule out drift as one of the factors.
Apologies to Aberdeen for speaking for him, but it seems to me that this must be the same logical trail he followed, a trail which led him to conclude that, “Here's an article published by Nature Communications about a study that suggests Europe's modern mtDNA signature was largely established about 6000 years ago, in the mid Neolithic, by people of an unknown origin who largely replaced the early Neolithic farmers, for reasons that aren't yet clear.”
The authors are clearly proposing that some genetic transition did indeed take place between the LBK or early Neolithic and the mid-Neolithic cultures before the arrival of Bell Beaker, Corded Ware, or Unetice. Now, this may not be supported by the data, it may indeed not be the best explanation of what actually happened in Europe, but it is unambiguously what they did say.
They are most definitely not saying that “ Europe's modern mtDNA signature was largely established about 6000 years ago as a result of migrations into Europe during the early Neolithic" to quote a post by Polako. Given the text of the main paper quoted above, it's also incorrect to maintain that the authors propose that “The descendants of early Neolithic farmers weren't replaced about 6000 years ago but were the ones who largely established Europe's modern mtDNA gene pool at this time." Clearly they are saying that there were indeed changes between the arrival of the first farmers and the Middle Neolithic of 6000 years ago. (4000 BC)
One can disagree with the conclusions of Brotherton et al, but one can’t re-write them; that just leads to frustration, confusion among readers, and further bad conclusions.
In addition to all of the above problems with this paper, I agree with Aberdeen that the authors are making a huge error in taking results from one area in Germany, and very small sample sizes for each specific time period, and presuming to then extrapolate from that to make broad generalizations about the peopling of Europe.