The news has been floating around in the anthropology and human population genetic circles for some time but it was not formally confirmed until now: a very ancient Y-DNA lineage appears to be so old that it can hardly be considered to be strictly Homo sapiens at its ultimate origin. The lineage is extremely rare however and has only been found so far in two men: an African-American (from the USA?) and eight Mbo individuals from Western Cameroon.
Fernando L. Méndez et al., An African American Paternal Lineage Adds an Extremely Ancient Root to the Human Y Chromosome Phylogenetic Tree. AJHG 2013. Pay per view (free 6 months after publication) → LINK [doi:10.1016/j.ajhg.2013.02.002]
Abstract
We report the discovery of an African American Y chromosome that carries the ancestral state of all SNPs that defined the basal portion of the Y chromosome phylogenetic tree. We sequenced ∼240 kb of this chromosome to identify private, derived mutations on this lineage, which we named A00. We then estimated the time to the most recent common ancestor (TMRCA) for the Y tree as 338 thousand years ago (kya) (95% confidence interval = 237–581 kya). Remarkably, this exceeds current estimates of the mtDNA TMRCA, as well as those of the age of the oldest anatomically modern human fossils. The extremely ancient age combined with the rarity of the A00 lineage, which we also find at very low frequency in central Africa, point to the importance of considering more complex models for the origin of Y chromosome diversity. These models include ancient population structure and the possibility of archaic introgression of Y chromosomes into anatomically modern humans. The A00 lineage was discovered in a large database of consumer samples of African Americans and has not been identified in traditional hunter-gatherer populations from sub-Saharan Africa. This underscores how the stochastic nature of the genealogical process can affect inference from a single locus and warrants caution during the interpretation of the geographic location of divergent branches of the Y chromosome phylogenetic tree for the elucidation of human origins.
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| Figure 1. Genealogy of A00, A0, and the Reference Sequence Lineages on which mutations were identified and lineages that were used for placing those mutations on the genealogy are indicated with thick and thin lines, respectively. The numbers of identified mutations on a branch are indicated in italics (four mutations in A00 were not genotyped but are indicated as shared by Mbo in this tree). The time estimates (and confidence intervals) are indicated kya for three nodes: the most recent common ancestor, the common ancestor between A0 and the reference (ref), and the common ancestor of A00 chromosomes from an African American individual and the Mbo. Two sets of ages are shown: on the left are estimates (numbers in black) obtained with the mutation rate based on recent whole-genome sequencing results as described in the main text, and on the right are estimates (numbers in gray) based on the higher mutation rate used by Cruciani et al.6 |
Their presence may also suggest minor admixture between the first migrant H. sapiens to arrive to Cameroon and their then still close relatives from previous flows, which we don't consider H. sapiens because we have drawn a convenient, but as we see now somewhat blurry, anthropometric or paleoanthropological line at Omo 2 and later specimens close to us in skull shape. While there is some generic comparability, the fact of admixture between such closely related populations is much less impressive than the one of admixture with Neanderthals or, probably, Homo erectus (non-Neanderthal Denisovan relatives), more distant from us in the tree of Greater Humankind.
As for the "molecular clock" estimate I suspect that this one is correct. I would have liked to explain it today but it will have to wait because it is a complex matter and I have been all day writing for this blog, so I am quite tired now.
Update (Mar 3): Kalupitero commented in another entry that this lineage has very distinctive STR markers and that he has spotted 9 Cameroonians and one French (probably of African ancestry) with it at the Sorenson Molecular Genealogy Foundation database.
Update (Mar 5): A reader directed me to a free copy of this paper, from where I selected fig. 1 (above) and fig. 3 (below). I realized that the number of sequences detected among the Mbo was not one as I originally said but eight. They also mention that the frequency of this lineage in Africa must be very low: c. 0.19% (CI: 0.11-0.35%).
Update (Mar 3): Kalupitero commented in another entry that this lineage has very distinctive STR markers and that he has spotted 9 Cameroonians and one French (probably of African ancestry) with it at the Sorenson Molecular Genealogy Foundation database.
Update (Mar 5): A reader directed me to a free copy of this paper, from where I selected fig. 1 (above) and fig. 3 (below). I realized that the number of sequences detected among the Mbo was not one as I originally said but eight. They also mention that the frequency of this lineage in Africa must be very low: c. 0.19% (CI: 0.11-0.35%).
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| Figure 3. Median-Joining Network of A00 Haplotypes The network is based on haplotypes (constructed with 95 Y-STRs) of eight Mbo and an African American (AA) individual. All mutations are assumed to be single step and were given equal weight during the construction of the network. Marker names are indicated without ‘‘DYS’’ at the beginning. |
See also:
- YSOGG: haplogroup A (not yet updated at the time of writing this)
- M. Hammer et al., Genetic evidence for archaic admixture in Africa. PNAS 2011.
- The early expansion of H. sapiens in Africa (mtDNA) (comparing with those mtDNA expansion maps, my work of years ago, suggests that the admixture should have happened with the expansion of the L1 or L1c population, at the Western edge of early Homo sapiens expansion as told by mtDNA).
"the fact of admixture between such closely related populations is much less impressive than the one of admixture with Neanderthals or, probably, Homo erectus (non-Neanderthal Denisovan relatives), more distant from us in the tree of Greater Humankind".
ReplyDeleteAgreed. We can hardly call something two lineages that separated a mere 300,000 years ago separate species.
"which we don't consider H. sapiens because we have drawn a convenient, but as we see now somewhat blurry, anthropometric or paleoanthropological line at Omo 2 and later specimens close to us in skull shape".
And that blurry line probably stretches back to neanderthals and Denisovans in fact.
"The first documented "modern human" skull, Omo 2, is dated to 190 Ka ago and it shares locality with another one, Omo 1, which is rather H. rhodesiensis, so in that 'dawn of modern humankind' there was surely not a very clearly drawn line between modern humans or Homo sapiens and archaic humans or Homo rhodesiensis (or whatever)".
Yes. A gradual process. Not a sudden jump.
"It could still be a very early diverging H. sapiens lineage"
I doubt we caould call it 'Homo sapiens' at that time though.
How common is this non-homo sapiens lineage in the Mbo???
DeleteI do not know at this time. I just know that only one individual has been found to carry it among the Mbo (and another one in America, with African ancestry). It's probably very rare even for the Mbo but can't be sure.
DeleteI am rather relieved that finally in 2013 we have found a non-autosomal lineage of (somewhat) archaic origin in living persons. Enough OoA people have had DNA tests to made survival of Neanderthal Y or MtDNA sequences extremely unlikely. But, I still hold out hope that somewhere in the mountains of PNG, Denisovan Y or MtDNA sequences will be found.
ReplyDeleteThere's also an X-DNA lineage which is very likely Neanderthal. Not sure if X-DNA should be considered "autosomal" but I understand that they tested the non-recombinable regions of the X chromosome, so that makes it a haploid lineage in any case.
Delete"I understand that they tested the non-recombinable regions of the X chromosome"
ReplyDeleteI don't think there are any 'non-recombinable regions of the X chromosome'. It is just that any mutations in the X chromosome can only be passed on by women as men's X chromosome is not passed on. So, in some ways, it is 'haploid'. Of course your comment re. Neanderthal elements stands.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0000557
Delete"We reasoned that by identifying genetic markers on human X chromosome regions where recombination is rare or absent, we should be able to construct X chromosome genealogies analogous to those based on Y chromosome and mitochondrial DNA polymorphisms"...
"I don't think there are any 'non-recombinant' regions of the X chromosome. It is just that any mutations in the X chromosome can only be passed on by women as men's X chromosome is not passed on."
DeleteEvery man passes one X chromosome onto a daughter. I realize this was a man who was tested in the US and that he would not get an X chromosome from a father, but the statement leads to confusion about X chromosomes in general.
Sorry. Of course the male X chromosome is passed on, but only to females.
ReplyDeleteThank you for clarifying that. Ignore my post above.
DeleteMitochondrial DNA of Neanderthals was separated from Homo sapiens much earlier than nuclear DNA. The reason can be, that Neandertals are the mixture of old Homo heidelbergensis (their mtDNA was left in neanderthal) and archaic Homo sapiens (their DNA contribution is much more made by men so we see it now only as part of nuclear DNA). I think this population of archaic Homo sapiens could have A00 chromozom Y. Than, the neanderthals could have it as well. Those archaic Homo sapiens (with A00) who left Africa around 400k BP left their traces in Close east (http://www.sciencedaily.com/releases/2010/12/101230123554.htm) and widespread as far as to India (Narmada skull) and even to China (http://en.wikipedia.org/wiki/Dali_(fossil)).
ReplyDeleteI think that the main reason is that they have made wrong measures (largely underestimating by a lot the Pan-Homo split). However it is possible that there may be something of what you say in addition to that.
Delete"We reasoned that by identifying genetic markers on human X chromosome regions where recombination is rare or absent"
ReplyDeleteThanks. I was not aware of any such region.
"Their presence may also suggest minor admixture between the first migrant H. sapiens to arrive to Cameroon and their then still close relatives from previous flows, which we don't consider H. sapiens because we have drawn a convenient, but as we see now somewhat blurry, anthropometric or paleoanthropological line"
I have been becoming more and more convinced that the modern human Y-chromosome arose in West Africa and the mt-DNA arose further east, perhaps as far as Kenya. As well as the recently revealed A00 we find A0 is probably a Central/West African haplogroup. As is A1a. It is only with A1b that we see any wide expansion. Even most B haplogroups are primarily West African. Maju's recent post, 'Non-additive genetic models ..." is very likely relevant here. The origin of Homo erectus may be a population demonstrating hybrid vigour when the two lines met up.
"Mitochondrial DNA of Neanderthals was separated from Homo sapiens much earlier than nuclear DNA. The reason can be, that Neandertals are the mixture of old Homo heidelbergensis (their mtDNA was left in neanderthal) and archaic Homo sapiens"
To me it is far more likely that it indicates periodic admixture between two semi-isolated groups as they gradually separated. We find similar phenomena in other species. Mitochondrial DNA differentiation does not necessarily proceed hand in hand with overall genetic separation. To me A00 actually represents the haplogroup ancestral to the modern Y-DNA.
Updated entry: not one but eight Mbo were found with this A00 haplogroup.
ReplyDelete"Updated entry: not one but eight Mbo were found with this A00 haplogroup".
ReplyDeleteWhich indicates reasonably conclusively that it is not the product of some random introgression event. It is much more likely to be an ancient survivor of the ancestral modern human Y-DNA.
And totals a 0.2% of African Y-DNA (as estimated by the authors). Probably less (my estimate, as it is concentrated in this unique forest population of Cameroon).
DeleteIt's possible in theory that it is an odd survivor from a more diverse Y-DNA pool among Homo sapiens, but then why is it found only far away from where the highest mtDNA diversity is, towards the Nile? Also there is at least one study (don't have time right now to search for it, sorry) which suggested that West Africans could have some local archaic admixture, just as Eurasians have Neanderthal one. On its own it seemed just statistical speculation but with this it seems to gain some weight.
"but then why is it found only far away from where the highest mtDNA diversity is, towards the Nile?"
ReplyDeleteTo me the obviousle xplanation is that the modern Y-DNA and mt-DNA arose in two different populations. As I said in an earlier comment here, 'I have been becoming more and more convinced that the modern human Y-chromosome arose in West Africa and the mt-DNA arose further east, perhaps as far as Kenya'.
"Also there is at least one study (don't have time right now to search for it, sorry) which suggested that West Africans could have some local archaic admixture"
Yes. That is a possible explanation for the survival of A00 in the modern human population of the region. But I'm sure I remember that the admixture was claimed to be from a population that had separated from modern humans long before a mere half million years ago.
"On its own it seemed just statistical speculation but with this it seems to gain some weight".
But the whole modern Y-DNA seems to have originated in West Africa, not in East africa where it is almost certain that the modern mt-DNA line arose. Cameroon is also home to the Bakola Pygmies, who have A0 Y-DNA. That haplogroup has not been found in the east either. A01a is also centred on Cameroon. Even A1a tends to be 'northwest African', specifically Guinea-Bisau, Mandinke and Dogan. It is only with A1b1 that we begin to find Y-DNA haplgroups beyond West Africa.
Turning to mt-DNA: the Bakola Pygmies have mt-DNA L1c1a, almost confined to 'western' Pygmies, with lesser amounts of L1c4 and L1c2a, but both these last two haplogroups are more generally 'west African'. So it was not until L1 reached West Africa that the Y-DNA 'Adam' line met the mt-DNA 'Eve' line. Meanwhile at the other end of mt-DNA L's geographic range L0d and L0k were already entering South Africa.
"To me the obviousle xplanation is that the modern Y-DNA and mt-DNA arose in two different populations".
DeleteIt does not work that way: Y(xA0, A00, xA1a) fits well with the East African mtDNA origin model. These lineages seem exceptional, not the rule.
"So it was not until L1 reached West Africa that the Y-DNA 'Adam' line met the mt-DNA 'Eve' line".
Surely not that way. People (early H. sapiens with Y-DNA Y(xA00,A0,A1a) and mtDNA L1c surely first) reached Central Africa and met some relatives, whose genetic pool was incorporated to a minimal extent.
Another obvious scenario that isn't really being considered is that this rare lineage could just as easily have been transported to West Africa from East Africa, as the vast majority of West African YDNA lineages are a subset of the the East African E-P2. So too with Cameroon, most Cameroonian YDNA lineages are E-P2+, these very rare but newly found deep lineages could have been transported with the more numerous lineages from EAfrica to WAfrica in the distant past and just simply went extinct in EAfrica but very few survived in the West.
ReplyDeleteThe only support I can imagine for such a stand is the apparent sweep by Y-DNA E in the L2+L3'4'6+L5 mtDNA area from the Red Sea to Lake Chad, which also explains the lack of other postB/pre-E clades aboriginal to Africa (notably D and CF or anything comparable). This might have also swept other small lineages like said A00, A0 and A1a, which are only found from Cameroon to the NW (at least so far).
DeleteBut I feel that we are losing Occam's Razor here, especially because A00 (and probably also A0) seem pre-Sapiens by age. Sudan and parts of CAR, Chad and the Congos, as well as all Gabon seem still largely unsampled anyhow.
I withheld my judgment but I'm suspecting a more near CAR or Northern Congos origin as a serious possibility.
Also in terms of autosomal DNA, the most diverse (studied) populations are the San from South Africa and the Bulala of Central Chad, followed closely by the San of North Botswana and the Fang (continental Equatorial Guinea and surroundings), in third position come the Sandawe of Tanzania, in 4th one the Bamun of Cameroon, the Igbo and Yoruba from Nigeria and the Maasai of East Africa, etc. In spite of back-flow from other regions, East Africa does not look the most diverse region. But then again they did not sample populations in Ethiopia or the Sudans, for example.
IF (I'm not sure right now) the Congo basin was drier in the Middle Pleistocene, some part of the earliest expansion of H. sapiens could well have happened via that area instead of following the, archaeologically better known, Rift region. That could explain some things but I'm unsure right now about how the archaeological and climatic data fits.
"But I feel that we are losing Occam's Razor here, especially because A00 (and probably also A0) seem pre-Sapiens by age".
ReplyDeleteYes, they are pre-sapiens. And why is that a difficulty? The sapiens Y-DNA must have ancestors. Homo sapiens may be a product of the mixing of the eastern and western versions of the pre-sapiens population of 'Sudan and parts of CAR, Chad and the Congos, as well as all Gabon'. Hybrid vigour? Personally I would doubt the Congo Basin was important very early in sapiens evolution, although:
"IF (I'm not sure right now) the Congo basin was drier in the Middle Pleistocene, some part of the earliest expansion of H. sapiens could well have happened via that area"
That would be very revealing. I don't know the climate there at the relevant time either. An interesting project to try to find out.
"It does not work that way: Y(xA0, A00, xA1a) fits well with the East African mtDNA origin model".
How do you come up with that idea? A00, A0,A1a(xA1b1a1,A1b1b) along with several B haplogroups are confined to West Africa. It is almost impossible to make a case that any of these basal clades originated in East Africa.
"These lineages seem exceptional, not the rule".
The problem for what you're claiming here, though, is that they are basal clades within the modern human Y-DNA diversity. Why are you suddenly not accepting basal diversity as an indication of origin?
"People (early H. sapiens with Y-DNA Y(xA00,A0,A1a) and mtDNA L1c surely first) reached Central Africa and met some relatives, whose genetic pool was incorporated to a minimal extent".
You are now proposing genocide of Y-DNA basal haplogroups throughout Africa except for a small pool of survivors in West Africa. I admit that scenario is possible. But another question: why are you so certain that Y-DNA Adam and mt-DNA Eve were husband and wife? Surely that is a most unlikely assumption.
"I'm suspecting a more near CAR or Northern Congos origin as a serious possibility".
I'm very inclined to agree that is where the Y-DNA and mt-DNA lines met and mixed. One from further east and the other from further west.
"The only support I can imagine for such a stand is the apparent sweep by Y-DNA E in the L2+L3'4'6+L5 mtDNA area from the Red Sea to Lake Chad"
I agree that Y-DNA E has largely replaced Y-DNAs A and B through much of Africa. It may be that the sweep has eliminated A haplogroups completely in East africa but left remnants in West Africa. But surely using Occam's razor it is far easier to accept the A haplogroups are indigenous to West Africa. That is why they survived there until the present. A's descendants moved east and eventually gave rise to E, which then spread extensively through Africa.
"Another obvious scenario that isn't really being considered is that this rare lineage could just as easily have been transported to West Africa from East Africa, as the vast majority of West African YDNA lineages are a subset of the the East African E-P2".
But that proposal assumes no-one moved until the very downstream Y-DNA clade E1b1-P2 developed. To me that is a most unlikely scenario. Besides which we have E1b's relation, E1a-M33, obviously having originated in West Africa.
"So too with Cameroon, most Cameroonian YDNA lineages are E-P2+"
But you're again ignoring the fact that E is a downstream Y-DNA haplogroup, far removed from A00.
"these very rare but newly found deep lineages could have been transported with the more numerous lineages from EAfrica to WAfrica in the distant past and just simply went extinct in EAfrica but very few survived in the West".
So you too are proposing genocide. You are both searching for explanations capable of fitting your pre-existing belief to the evidence, not objectively looking at the evidence and then forming a conclusion.
"Yes, they are pre-sapiens. And why is that a difficulty?"
DeletePrecisely: establishing a divide between the Homo sapiens and the Homo rhodesiensis (I presume) is becoming a bit more difficult now.
"How do you come up with that idea?" [that Y(xA0, A00, xA1a) fits well with the East African mtDNA origin model].
Because it does. A1b (including now BT (B'CDEF)) correlates well with the modern human mtDNA structure with a probable center where I said before: somewhere between Lake Chad and Lake Victoria and apparent expansion West to the Chad-Gabon area and South to the Zambezi and beyond. The other three clades break this parallel.
In other words: mtDNA does not support a Western origin of Homo sapiens (nor does MSA archaeology nor skeletal remains, although there are many blanks in these surely).
"Why are you suddenly not accepting basal diversity as an indication of origin?"
I'm not rejecting that. All I say is that it appears to be a pre-Sapiens apparent origin and not yet a Sapiens one. Anyhow you know well that I always look with particular emphasis to the mtDNA structure, which is more stable and a lot harder to upset by gender-biased sweeps.
"You are now proposing genocide of Y-DNA basal haplogroups throughout Africa except for a small pool of survivors in West Africa".
More like genocide of the correlated mtDNA, which, it seems, left no survivors whatsoever. Right?
Why not? If we essentially "genocided" (or pushed to extinction by whatever means and within whatever time-frames) other Homo species in Eurasia, why not in Africa as well?
"why are you so certain that Y-DNA Adam and mt-DNA Eve were husband and wife?"
I did not say so. All I say is that (hunter-gatherer) populations include men and women alike and that, normally, they migrate together. So we should expect some sort of correlation between both haploid phylogenies and, in most cases at least, we do find that.
"I'm very inclined to agree that is where the Y-DNA and mt-DNA lines met and mixed".
So you imagine two different populations, species or subspecies converging and then all the male lineages of one side exterminated and all the female ones of the other as well. Sounds extremely far fetched to me (and is still "genocide").
I can understand that linear oversimplification but, for that very reason, I must discard it as well: it's too simplistic and unrealistic.
"But surely using Occam's razor it is far easier to accept the A haplogroups are indigenous to West Africa".
"A" is such a big word that it encompasses all the human phylogeny nowadays (BT is "brother" to A1b1 and descendant of A1b-root). Some are West or NW African obviously but these are specifically three and have names: A00 (Mbo), A0 (Cameroon Pygmies and Mozabites), A1a (Niger and Morocco). And all are found at very low frequencies. In fact most of them are not even found in West Africa proper (Central Africa instead, with some extension to NW Africa), only A1a is found in West Africa (Niger).
"establishing a divide between the Homo sapiens and the Homo rhodesiensis (I presume) is becoming a bit more difficult now".
ReplyDeleteSo you're finally facing facts on this subject. Until now you have always maintained there is a clear and well-defined dividing line between sapiens and any pre-modern species.
"A1b (including now BT (B'CDEF)) correlates well with the modern human mtDNA structure with a probable center where I said before: somewhere between Lake Chad and Lake Victoria"
So? You're avoiding the facts again. A1a can hardly be placed there. Nor can A0 or any of its derivatives. And now we have A00 definitely not placed there. Basal A1b is obviously the haplogroups that moved from West Africa. However I agree that H. sapiens is very likely to have originated in that region. But this latest data suggests the deeper pre-sapiens origin of the modern male and female haplogroups lie in different regions within Africa.
"The other three clades break this parallel".
Yes. Because they had nothing to do with East Africa.
"Some are West or NW African obviously but these are specifically three and have names: A00 (Mbo), A0 (Cameroon Pygmies and Mozabites), A1a (Niger and Morocco). And all are found at very low frequencies. In fact most of them are not even found in West Africa proper (Central Africa instead, with some extension to NW Africa), only A1a is found in West Africa (Niger)".
But these three are the only surviving early branches within the Y-DNA. I agree that none appear to have been originally able to move east beyond the Niger River, so perhaps 'Central West Africa' is a better region.
"In other words: mtDNA does not support a Western origin of Homo sapiens"
That statement is totally irrelevant to any discussion on the origin of the Y-DNA. Unless you're still claiming Y-DNA Adam and mt-DNA Eve were husband an wife. A situation I find most unlikely.
"I did not say so".
It is very difficult to see any other interpretation of what you're claiming. You seem to believe a small group of pre-sapiens woke up one morning to discover they were Homo sapiens. A situation I find extremely unlikely.
"Anyhow you know well that I always look with particular emphasis to the mtDNA structure, which is more stable and a lot harder to upset by gender-biased sweeps".
I repeat: that has absolutely nothing to do with the deeper origin of the Y-DNA.
"All I say is that it appears to be a pre-Sapiens apparent origin and not yet a Sapiens one".
But that West African pre-Sapiens A00 haplogroup is ancestral to all modern Y-DNA. Surely you can see that.
"More like genocide of the correlated mtDNA, which, it seems, left no survivors whatsoever. Right?"
Yes. And no surviving members of the male line that originally accompanied mt-DNA Eve. But surely that is hardly surprising. Neither Denisova nor Neanderthal have surviving haplogroups of either sex line. And you are well aware of that fact:
"Why not? If we essentially 'genocided' (or pushed to extinction by whatever means and within whatever time-frames) other Homo species in Eurasia, why not in Africa as well?"
"So you imagine two different populations, species or subspecies converging and then all the male lineages of one side exterminated and all the female ones of the other as well. Sounds extremely far fetched to me (and is still 'genocide')".
That is what the evidence suggests. I doubt we could call the two popualations 'species' however. Perhaps not even 'subspecies'. Just populations from the geographic extremes of a single subspecies.
"Unless you're still claiming Y-DNA Adam and mt-DNA Eve were husband an wife. A situation I find most unlikely".
ReplyDeleteSaid like that, me too. But I do expect Y-DNA "Adam" and mtDNA "Eve" were part of the same population, at the origin of modern humankind ("Sapienskind"), even if at different times or whatever. This only works IF we exclude A1a, A0 and A00 - and then it works way too well to be ignored.
According to my estimates A1a and A1b (incl. BT) diverged c. 200 Ka ago, what is roughly the origin of "Sapienskind" (A1b1 and BT would diverge soon after that). And A1b's scatter fits almost perfectly with the scatter of modern human mtDNA (L-all), so we should consider Y-DNA "Adam" to be A1b and the other Y-DNA lineages to belong to other relatives (no biblical metaphors available for this), who introgressed into our main ancestral genetic pool somehow.
It does however suggest (lacking other evidence) that the Y-DNA pool has a pre-Sapiens or proto-Sapiens in Central/West Africa. This added to the autosomal DNA diversity data, suggests (more research is still needed to be fairly certain) that the overall origin of "Sapienskind" is rather towards Lake Chad than towards Lake Victoria.
"But that West African pre-Sapiens A00 haplogroup is ancestral to all modern Y-DNA".
Actually not. It is precisely not ancestral but a divergent branch. What is ancestral is the precursor of A00 and A0-T ("Y"), but A00 is a divergent lineage, hence not-ancestral but to itself. Surely even you can understand that. Similarly A0 and A1a are not ancestral except to themselves, however A0-T is ancestral to all humankind (save A00) and A1 is ancestral to all humankind (save A00 and A0).
Finally only A1b is ancestral to most modern humans - maybe 99%? - (excepted the very rare A00, A0 and A1a), and is also the only one Y-DNA lineage which fits well with the mtDNA structure.
So for all practical purposes we should begin talking of modern Homo sapiens at A1b. Said, that, this does not exclude at all other inputs from related populations, as the rare A00, A0 and possibly also A1a demonstrate. Lacking fossils from those key areas we do not know how those related populations were: how much "sapiens" or how much "rhodesiensis" or whatever they looked like.
"And no surviving members of the male line that originally accompanied mt-DNA Eve".
How can you say that? A1b is "the man" (quite obviously). We do not know for sure but it seems plausible that the maternal ancestors of mtDNA "Eve" came from the same genetic pool as those of A1b.
No genocide needed at this stage to explain anything. No convergence of two gender-segregated populations coming from different origins either. Just that the mtDNA prior to "Eve" has been (it seems) lost forever, while the Y-DNA prior to A1b has left some remnants.
As far as I can tell, there was only one primary early Sapiens population. In Northern Central Africa rather than the Upper Nile? Maybe.
"That is what the evidence suggests".
It does not. We don't have data to directly gauge the precursors of mtDNA "Eve". So if Y-DNA came from the West (rather Central Africa, I'd say) before coalescing into A1b, that was most parsimoniously the likely origin of mtDNA as well (before coalescing into L-root).
"So for all practical purposes we should begin talking of modern Homo sapiens at A1b".
ReplyDeleteBut the subject of this post is A00.
"It is precisely not ancestral but a divergent branch. What is ancestral is the precursor of A00 and A0-T ('Y'), but A00 is a divergent lineage, hence not-ancestral but to itself. Surely even you can understand that".
'Ancestral' is a much shorter way of saying ' branched off from the common ancestor of all modern human Y-DNA haplogroups'.
"But I do expect Y-DNA 'Adam' and mtDNA 'Eve' were part of the same population, at the origin of modern humankind ('Sapienskind')"
'At the origin of modern humankind' possibly yes. But this paper is about a pre-sapiens Y-DNA. And even if I concede that 'Y-DNA 'Adam' and mtDNA 'Eve' were part of the same population' that population may have been widely dispersed. Although the distance from Cameroon to Sudan is considerable the available habitat may have been just a thin strip along the grassland/forest border region.
"According to my estimates A1a and A1b (incl. BT) diverged c. 200 Ka ago, what is roughly the origin of 'Sapienskind'"
I'm more than happy to accept that.
"so we should consider Y-DNA 'Adam' to be A1b and the other Y-DNA lineages to belong to other relatives (no biblical metaphors available for this), who introgressed into our main ancestral genetic pool somehow".
Again I accept much of that. But I would guess that the A00, A0 and A1a lineages simply entered the modern human gene pool when mt-DNA L1 arrived in West Africa. In fact A1b may have begun its own expansion eastward at that time. I would not be inclined to call it 'introgression'. The two 'species' were probably not particularly distinct. More like populations of the same species.
"How can you say that? A1b is 'the man' (quite obviously)".
Not 'obvioulsy' at all. Any mt-DNA haplogroup that branched off before L1b had reached West Africa would not have had any ancestral modern Y-DNA companion. That includes L0 and L2''6.
"It does however suggest (lacking other evidence) that the Y-DNA pool has a pre-Sapiens or proto-Sapiens in Central/West Africa".
Very strongly suggest.
"The overall origin of 'Sapienskind' is rather towards Lake Chad than towards Lake Victoria".
I don't believe we can narrow the region down to such a small area, although Cameroon actually reaches north as far as Lake Chad.
"it seems plausible that the maternal ancestors of mtDNA 'Eve' came from the same genetic pool as those of A1b".
To me the evidence is fairly convincing that the modern mt-DNA line originated somewhat east of Lake Chad.
"Lacking fossils from those key areas we do not know how those related populations were: how much 'sapiens' or how much 'rhodesiensis' or whatever they looked like".
The 'introgression' recently claimed for a West African archaic species was from beyong the Niger River, in Nigeria. The carriers of these A00, A0 and A1a haplogroups were most likely very little removed from H. sapiens.
"So if Y-DNA came from the West (rather Central Africa, I'd say) before coalescing into A1b, that was most parsimoniously the likely origin of mtDNA as well (before coalescing into L-root)".
To me there is absolutely no reason why the modern human mt-DNA line and the modern human Y-DNA need have arisen in the same region as each other. Once more you're basically claiming that Y-DNA Adam and mt-DNA Eve were husband an wife.
You guys do realize that "AA's" are the real hebrew israelites right? These new genetic discoveries, just proves what most of us already know!
ReplyDeleteVery funny, thanks for the joke.
DeleteI was about to send this comment above to spam limbo but it's so funny that I decided to publish in spite of its obvious pseudoscientific ethnocentric absurdity.
My apologies to those who don't think it's just hilarious.
I must point this out although it may seem trivial to some. "an African-American (from the USA?)." Is there a question somewhere? There is only one place in the world where people with African ancestry are referred to as African American. That is in the USA,... period.
ReplyDeleteAmerica is from the Artctic to Tierra del Fuego, hence American is anyone from that continent (or double continent, if you wish), Native American is someone native (more properly "aboriginal") from the continent and African American is someone from the continent with African ancestry. He or she can be from Bolivia for all I know.
DeleteThe usage of "America(n)" as endonym for USA people is arrogant, imperialist and simply wrong.
As an American from the USA, I take insult to your assumption. We do not feel we "own" the word or the 2 continents. It is just that we were raised to be proud of our country The United States of America!
DeleteI and many others take insult from your abusive imperialistic "pride", which is best embodied in Roosevelt's motto "America (the continent) for Americans (the US ones)". He was the one first invading Haiti, Nicaragua, Honduras and Panama.
DeleteYour usage of America meaning Angloamerica is offensive for all other Americans.
hello...to whom it may concern...my fbook name is SAMSON MORFAW and I was born in the very very area where according to this web page, we carry that y chromosome....I left Bangwa when i was only three years old in 1970. I'd like to have a dna test done on me..to see up to what extent the aricle of your your page is credible. fbook me. and we can chat about this discovery of 2013.
ReplyDeleteI don't use Facebook, sorry Samson (too intrusive in privacy, too authoritarian in politics, only good for trivial socialites IMO).
DeleteAnyhow, if you have any doubt about what I say, the original study is linked in the entry and by now it should be freely available to all.
Or chat here...
Samson, send a friend request to forka leypey mathew fomine and Bonnie Shrack. They are doing the testing now in Bangwa, Mbetta and Mbo. You can send me a request to: Laurie Purdy Middendorf
Deletealso, look up a00-cameroon research project on facebook and this on experiment.com https://experiment.com/projects/go-west-young-man-in-search-of-the-a00-haplogroup-among-peoples-of-western-cameroon?s=search
Deletehttp://haplogroup-a.com/Ancient-Root-AJHG2013.pdf
ReplyDeleteHi,
ReplyDeleteIt was said that, so far, the oldest y-dna haplogroup is A00. First, it was found in an African-American individual whose ancestor named Perry and then later it was also found in several people of Bangwa-Nweh tribe and Mbo tribe in Cameroon. So, that means the earliest people are not the Khoisan anymore right? Anyway, the link below is the picture of people with A00.
http://b2.ifrm.com/67/29/0/p707309/12716427_923427764439575_5125519943074767696_o_opt__1_.jpg
So, could the earliest Homo Sapiens possibly look like them?
What Capra says below is pretty much as I would put it: there's no "earliest people" (we all descend from the same earliest H. sapiens, minus whatever lesser admixture with other archaic humans, which is different by populations but small anyhow) and Y-DNA is just one marker (people with the same haplogroup can look very different, for example there's R1b people in Cameroon, Europe and the Uyghur Country, R1a is dominant in Poland and Uttar Pradesh alike, E1b in much of Africa but also Greece and Albania, N among Buryat Mongols and Estonians alike, etc.) It's simple to understand: imagine that your great-great-grandfather was African but migrated to Europe and, generation after generation, your paternal ancestors married European women, you'd look European and your autosomal DNA would only produce (on average) 1/16 African, which is like 6%. Make it a a few generations more (2-3 centuries total) and there would be no trace of that African ancestry except for the Y-DNA, which does not recombine. When we are talking of populations (which tend to some degree of endogamy) it takes more time to erase that overall genetic ancestry but pre-history takes place in terms of millennia (c. 200,000 years since Omo 1, the first known Homo sapiens, 125,000 years since the out-of-Africa migration, 50,000 years since the arrival of H. sapiens to Europe, some 9000 since Neolithic, 5000 since the pyramids) so there is much more time to dissolve those exotic ancestries into the wider host population, in some cases retaining the exotic Y-DNA or some other genes/markers however. That's why Finnish people are like 50% N1, arrived from East Asia in the Epipaleolithic (most likely) but they are around 90% European in autosomal DNA. That's why Greeks may carry African-originated E1b-M78 in 1/3 of the cases but they still look as European as the Finns or the Brits in overall genetics (a bit more West Asian maybe but not obviously African anyhow). Etcetera.
DeleteSo how did the earliest H. sapiens look? We can't know for sure but I'd think that maybe averaging modern African diversity could give us a good approximation. I'd say they were almost certainly "black" (brown) in skin color and had curly hair, probably African type. Why? Because these traits are not just found in all African "aboriginal" populations but also in those Eurasian groups that have lived isolated in tropical areas since very long ago (Andamanese, Filipino Negritos, Papuans, Australian Aborigines, which are not generally related to each other more than to Europeans or Chinese). Also it seems quite likely that straight hair is a Neanderthal introgression (how did Neanderthals evolve it?, can't say). Other "innovative" traits like "white" (beige) skin color may well be spontaneous adaptions, as they are necessary in order for child health and survival in climates where sunlight is scarce (particularly in winter), as we produce a key vitamin (D) mostly in the skin. It can be obtained from fish as well but otherwise it's effectively impossible to obtain from the diet.
Anyhow. I am of the opinion that A00 and quite probably also A0 rather than being the oldest Homo sapiens lineages, they seem to reflect an admixture with a closely related population that can be considered an "archaic human". Why? Because the mtDNA trail does not bring us to a "cradle" in Central-West Africa but in East Africa rather to the North (Sudan, Ethiopia, Uganda). See the maps here: http://forwhattheywereweare.blogspot.com/2013/04/synthesis-of-spanish-language-series-on.html
DeleteAlso there was one study that suggested that both the West African and the Southern African early branches of humankind probably had some sort of admixture with local archaics, just as the macro-Asian branch had with neanderthals. See: http://www.pnas.org/content/108/37/15123.full
It's therefore at least plausible that the archaic admixture in West-Central Africa was with a closely related population to the early Homo sapiens that incorporated ancient Y-DNA branches A00 and A0 (A1 already stems from East Africa, being consistent with the mtDNA mapped phylogeny). At the moment we know nothing about archaic African genetics directly (and in jungle areas, fossils are extremely scarce anyhow), so we will have to wait for direct confirmation.
There are no "earliest" people alive now, unless they went through a time warp! Since the first modern humans everyone alive today has been evolving for the same amount of time, so there is no reason Mbo or Khoisan or any other particular population would be more similar to the first humans than any other. They are all equally related to the first Homo sapiens.
ReplyDeleteWhen someone says Khoisan are the "earliest" they mean that all other people are more closely related to each other than any of them are to Khoisan. So Khoisan form one branch of the tree of humanity and everyone else forms another branch. But neither branch is actually "earlier", they are the same age.
As for the Y chromosome, it represents only a small part of your ancestry, which is passed on from father to son. A00 is the oldest branch of this kind of ancestry. But there is also maternal ancestry, and there Khoisan have very old branches (L0d and L0k). Most important is autosomal ancestry, which is most of your genomes and passed on from both parents. There it is Khoisan who split off first by most analyses (though I have seen one where Pygmies were first).
Also, when people are putting populations in a tree and saying Khoisan are the first branch, Pygmies are the second, etc, or saying that Khoisan separated from other humans 120 000 years ago or whatever, that does not mean really that Khoisan became and remained separated from everyone else long ago down to the present. Everyone has a mix of ancestry, it is just that the Khoisan have the largest amount of ancestry from early separated populations.
Soo pre sapien much older
ReplyDelete