Haplogroup C mtDNA in Caucasoids does not necessarily indicate "Mongoloid" admixture

Dienekes writes:
Jean M links to a Master's thesis, which discovered the following:
While most of our samples possessed mtDNA haplotypes that can be linked to European and Near Eastern populations, three Neolithic and all three Bronze Age individuals belonged to mtDNA haplogroup C, which is common in East Eurasian, particularly South Siberian, populations but exceedingly rare in Europe. Phylogeographic network analysis revealed that our samples are located at or near the ancestral node for haplogroup C and that derived lineages branching from the Neolithic samples were present in Bronze Age Kurgans. In light of the numerous examples of mtDNA admixture that can be found in both Europe and Siberia, it appears that the NPR and South Siberia are located at opposite ends of a genetic continuum established at some point prior to the Neolithic. This migration corridor may have been established during the Last Glacial Maximum due to extensive glaciation in northern Eurasia and a consequent aridization of western Asia. This implies the demographic history for the European gene pool is more complex than previously considered and also has significant implications regarding the origin of Kurgan populations.

[. . .] The Dnieper-Donets population was described as robust Europeoid by Soviet anthropologists as was the Andronovo/Afanasevo tradition further east. It is interesting that Mongoloid admixture has been detected in both groups. I would not have guessed that this would have extended that far west and south. It seems that M. G. Levin may have been right when he stated that the Mongoloid elements penetrated far into eastern Europe.

I see no reason to believe the presence of haplogroup C indicates a "Mongoloid component". Stephen Oppenheimer sees C/Z mtDNA entering Mongoloids as part of an "intrusive" element "likely to have arrived from farther west in Asia, along with the eastern spread of the Upper Palaeolithic technology that appeared in Kara Bom in the Russian Altai 43,000 years ago." If this is correct, the presence of C in robust steppe Caucasoids would not be surprising. Oppenheimer has C/Z originating in western South Asia and entering Central Asia "round the western end of the Himalayas" 40-50,000 years ago, whereas Mongoloids (and "real" East Eurasian haplogroups) ultimately originate in SE Asia. Rather than indicating Mongoloid admixture "penetrated far into Eastern Europe", the presence of C mtDNA this early and this far west means one can't simply write off C and Z lineages in more easterly ancient Caucasoids (like some of those those buried at Xiaohe) -- or in Icelanders, for that matter -- as the product of Mongoloid admixture.

From Oppenheimer's Out of Eden:

There is still the puzzle of where those 'intrusive' founders of the Mongoloid Mammoth Steppe colony (C, X, and Z) came from in the first place, and which of the three possible corridors into the Mammoth Steppe they took. These three north Eurasian lines are very uncommon south of the Himalayas. The sister branches C and Z reach their highest rates in Siberia and Northeast Asia, and are hardly found farther south at all except in India, Mongolia, Central Asia, and Tibet. They stretch in a broad east-west continuum across the Asian Steppe, achieving significant rates in Central Asia and even as far west as Turkey. Group C even got to America via Alaska, yet their northerly distribution in East Asia suggests they could not have moved up north from South east Asia via China. Rather, they are more likely to have arrived from farther west in Asia, along with the eastern spread of the Upper Palaeolithic technology that appeared in Kara Bom in the Russian Altai 43,000 years ago. They belong to the Manju group, and their ultimate ancestors appear to come from Pakistan or India, having moved up the valley of the Indus via Kashmir or Afghanistan round the western end of the Himalayas. This all suggests that they moved in to the Asian Steppe between 40,000 and 50,000 years ago from west Central Asia. Consistent with the concept that C and Z spread east across the steppe with Upper Palaeolithic technology, Toomas Kivisild has estimated the age of C in Mongolia at 42,000 years. [. . .]

The complicated mitochondrial picture described above suggests that Mongoloids derive primarily from the south, while Central Asian people come mainly from a West Asian source, but combined with additional East and Southeast Asian sources in Central and Northeast Asia. This genetic evidence then supports the geographical theory of a three-pincer colonization of Central Asian from the Indo-Pacific coast about 40,000-50,000 years ago. The dissection of the various admixed genetic contributions to Northeast Asia clarifies and is consistent with the concept of an ultimately Southeast Asian origin of Mongoloids peoples.


n/a said...

Response to a subsequent comment by Dienekes:

Haplogroup C mtDNA has likely been subject to selection relating to extreme cold, meaning those dates likely underestimate its age. Selection could also play a role in the low frequencies in living Europeans.

Effects of purifying and adaptive selection on regional variation in human mtDNA

The relative frequency and amino acid conservation of internal branch replacement mutations was found to increase from tropical Africa to temperate Europe and arctic northeastern Siberia. Particularly highly conserved amino acid substitutions were found at the roots of multiple mtDNA lineages from higher latitudes. [. . .]

On the basis of this biogeographic analysis, we would expect haplogroups A, C, D, and X to have been subjected to much greater cold stress than haplogroup B or African macro-haplogroup L. Accordingly, the I/T ratios of the arctic haplogroups A, C, D, and X (0.91 to 2.91) were all greater than B (0.75) or L (0.70), and the RFI values of haplogroups A and X were significantly greater than that of L (P 0.05) (Table 2). Moreover, the CII values of haplogroups A (53%) and C (73%) were much higher than B (31%) or L (36%), with the CI of C being the highest of any haplogroup (Table 2). Hence, the mtDNA variation of haplogroups A, C, D, and X has been strongly influenced by adaptive selection, whereas that of haplogroup B has not. [. . .]

The Siberian sub-haplogroup C also contained two conserved root variants: ND4 at nt 11969A (A404T) (CI 85%) and cytochrome b (cytb) at nt 15204C (I153T) (CI 85%).


Mutation Rate Switch inside Eurasian Mitochondrial Haplogroups: Impact of Selection and Consequences for Dating Settlement in Europe

This analysis revealed a new coalescence age for R at 54.500 years, as well as several limitations of standard dating methods, likely to lead to false interpretations. These findings highlight the association of a striking under-accumulation of synonymous mutations, an over-accumulation of non-synonymous mutations, and the phenotypic effect on haplogroup J. Consequently, haplogroup J is apparently not a Neolithic group but an older haplogroup (Paleolithic) that was subjected to an underestimated selective force. These findings also indicated an under-accumulation of synonymous and non-synonymous mutations localized on coding and non-coding (HVS1) sequences for haplogroup R0, which contains the major haplogroups H and V. These new dates are likely to impact the present colonization model for Europe and confirm the late glacial resettlement scenario. [. . .]

Similarly, we propose that the J lineage had the same mutation rate as the other lineages, but preferentially accumulated non-synonymous mutations, possibly due to positive selection of non-synonymous mutations in a cold environment. In fact, it was previously proposed that the non-synonymous mutation of the J haplogroup would promote heat production by decoupling oxidative phosphorylation, thus constituting a mitochondrial adaptation to cold weather [6].


This paper estimates a coalescence age of 31kya for C, but estimates ages of 40kya for its sister haplogroup Z and 58kya for CZ.

Anonymous said...

'"It's not extremely cold in Europe, certainly not in relation to Siberia."

That's the point. MtDNA that throw off more heat at the expense of efficiency are likely to be adaptive among hunter-gatherers living in the far north or in the middle of an ice age, but maladaptive among agriculturalists with expanding populations to feed in more temperate climes/times.'

Lol, dienekes got pwned.

Anyways, what leads you to believe that mt group C is adapted specifically for the cold, is costly in temperate environments?

n/a said...

"Anyways, what leads you to believe that mt group C is adapted specifically for the cold, is costly in temperate environments?"

Douglas Wallace and others have been arguing for years that patterns of mutations in some mtDNA lineages (including haplogroup C) indicate such adaptation has occurred.

Natural selection shaped regional mtDNA variation in humans
mtDNA Mutations May Permit
[. . .]
Adaptation to Changes in Diet and Climate.
mtDNA variation would be the ideal method to foster adaptation to different environments. Mitochondrial oxidative phosphorylation (OXPHOS) uses dietary calories to generate ATP to do work and heat to maintain body temperature. The balance between these two functions is determined by the efficiency of coupling the mitochondrial inner membrane electrochemical gradient to synthesize ATP through the ATP synthase. Variants that reduce the coupling efficiency would reduce ATP production, but increase heat production. Such variants would be advantageous in the subarctic and arctic where survival of cold stress would be a major factor in survival. Partial uncoupling of the mitochondria would increase the basal metabolic rate of the individual and hence would require a higher caloric intake, such as that provided by a high-fat diet. Thus, mtDNA ATP6 variants that reduce coupling might partially account for the increased basal metabolic rate that has been observed in indigenous, circumpolar, human populations (29).
[. . .]
Given that mtDNA lineages are functionally different, it follows that the same variants that are advantageous in one climatic and dietary environment might be maladaptive when these individuals are placed in a different environment.
[. . .]
If selection has played an important role in the radiation of human mtDNA lineages, then the rate of mtDNA molecular clock may not have been constant throughout human history. If this is the case, then conjectures about the timing of human migrations may need to be reassessed.