The Levant versus the Horn of Africa: Evidence for Bidirectional Corridors of Human Migrations

The Levant versus the Horn of Africa: Evidence for Bidirectional Corridors of Human Migrations

J. R. Luis, D. J. Rowold, M. Regueiro, B. Caeiro, C. Cinnioglu, C. Roseman, P. A. Underhill, L. L. Cavalli-Sforza, and R. J. Herrera1

Paleoanthropological evidence indicates that both the Levantine corridor and the Horn of Africa served, repeatedly, as migratory corridors between Africa and Eurasia. We have begun investigating the roles of these passageways in bidirectional migrations of anatomically modern humans, by analyzing 45 informative biallelic markers as well as 10 microsatellite loci on the nonrecombining region of the Y chromosome (NRY) in 121 and 147 extant males from Oman and northern Egypt, respectively. The present study uncovers three important points concerning these demic movements: (1) The E3b1-M78 and E3b3-M123 lineages, as well as the R1*-M173 lineages, mark gene flow between Egypt and the Levant during the Upper Paleolithic and Mesolithic. (2) In contrast, the Horn of Africa appears to be of minor importance in the human migratory movements between Africa and Eurasia represented by these chromosomes, an observation based on the frequency distributions of E3b*-M35 (no known downstream mutations) and M173. (3) The areal diffusion patterns of G-M201, J-12f2, the derivative M173 haplogroups, and M2 suggest more recent genetic associations between the Middle East and Africa, involving the Levantine corridor and/or Arab slave routes. Affinities to African groups were also evaluated by determining the NRY haplogroup composition in 434 samples from seven sub-Saharan African populations. Oman and Egypt's NRY frequency distributions appear to be much more similar to those of the Middle East than to any sub-Saharan African population, suggesting a much larger Eurasian genetic component. Finally, the overall phylogeographic profile reveals several clinal patterns and genetic partitions that may indicate source, direction, and relative timing of different waves of dispersals and expansions involving these nine

Thanks for posting this. I am still unable to correlate the world Y chromosome phylogenetic chart with the mtDNA as the Y chromosome tree appears to have an early step , M89, for which there is no known equivalent in the mtDNA. Quoting from the article:

'Both the Horn of Africa and the Levantine corridor have been proposed as main passageways for migrations of anatomically modern humans out of Africa (Cavalli- Sforza et al. 1994; Lahr and Foley 1994). The distributions of [Y chromosome] haplogroups C and D suggest early dispersals (50-45 thousand years [ky] ago) of ancestors of these lineages from the Horn of Africa to southern Asia (Underhill et al. 2001b), most likely in conjunction with mtDNA haplogroup M (Quintana-Murci et al. 1999; Kivisild et al. 1999).'

While the presence of 'M' mtDNA haplogroups in Africa may be due to back-migration as previously illustrated in Forster's slide 11, I have previously thought that RPS4Y ('haplogroup C' correlated with mtDNA M. So, so far so good.

' Posterior demic movements, such as the one represented by the dissemination of the ancestral M89 chromosomes and the 10873T mtDNA lineage to Eurasia, most likely occurred via the Levantine corridor, ~45 ky ago (Underhill et al. 2001b; Quintana-Murci et al. 1999).

Here, it is suggested that the M89 Y chromosomes correlate with mtDNA macro-haplogroup N and this is where I run into difficulty as I don't know of any European or Eurasian mtDNA haplogroups which should be closer to those of Africans than any found in Australia or the New World.

...you put your Y-chromosome in, take a X-chromosome out and shake it all about - that's what a male is all about....

Why are you (or anyone) trying to correlate Y-chromosomes with mtDNA? Surely the Y-chromosomes will be able to chance without a corresponding change in mtDNA (and vice versa) - which ultimately leads to a conclusion 'no correlation'? That any apparent 'correlation' is just a chance happenstance.

'The third large sub-cluster of M168 lineages is characterized by the M89/M213 mutations at the root of Groups VI-X. As discussed above, this sub-cluster is suggested to have evolved in East Africa, from where it dispersed to Eurasia through the Levantine corridor around 45000 years ago. This dispersal would have also involved several mtDNA haplogroups characterized by the 10873 C

Well I suppose that is a good answer to a rhetorical question... a rhetorical answer?

I still don't like that time frame they give.

But 'correlation' is a statistical function that leads to universal conclusions on a probability factor. However, the Y-chromosome and mtDNA live separate lives and the twain never meet, even though they get rather close to each other! In order to 'correlate' Y-chromosomnes to mtDNA, you would have to argue a function of one acting on the other as in a fatal attraction. AFAIK no such function exists. Also it would mean it would always occur. You say it doesn't. Therefor another reason must exist.

IIRC the Y-chromosome Adam is only some 80K years old, when the mtDNA Eve is some 120 -> 170K years old (depending on claimant). One thing is certain, there can not have been 'immaculate conceptions' for some 40 -> 90 K years. Think of all the bibles one would have to generate... It would be fair to say that there must have been a few milk men, gas meter readers etc to serve the function of the missing Adam in that time. They too must have met an untimely end -probably as a result of Adam coming home unexpectedly.

I don't see a problem with an extinction of a lineage. It has happened before as the DNA Adam and Eve's show us and I'm sure there are more of them.

Snippage. . . . .

Afraid that you may have missed a point. I dont think that either I or the good Ms. Horvat were suggesting that the Y-chromosome and mtDNA were intertwined in some intracellular manner, mearly in the external 'physical world' sense. Except in very special cases, where mtDNA goes, so goes the Y-chromosome. If you were to trace a map of human migrations, using the respective genetic lines, they should for the most part overlay, i.e. the 'same' answer from two different and distinct sources.

Dont know if it was accidental or intentional, but recommend a review of what was being discussed.

Regards

The fact that Y-chromosome and mtDNA exists in the same cell (but different parts), wasn't really the issue at all. What I suggested was that a mathematically predictable correlation between a particular mtDNA and Y-chromosome doesn't seem to be logical - IF that was being suggested. That such would result in, is an argument to say, 'Because mtDNA XXXX is found here, Y-chromosome YYYY will be found in the male population, the probability factor that this will be so is 95.4%.'

For that statistical argument to apply, a 'fatal attraction' would have to exist between females of a particular mtDNA, and males of a particular Y-chromosome. That each had an attribute of unique desire to the other, to the exclusion of others (perhaps a hairy arse would do the trick?)

I note your argument against the molecular clock, and I agree to a large degree with you. Likewise, in this case, I would not accept a statistical predictor for the existence of any particular DNA in a gender because of the existence of another in the opposite gender.

On the other hand, I also don't say that a co-existence does NOT occur, I also say that it NEED NOT occur. Further more I do not say that the occurrence Gisele has identified does not exist - only that a 'correlation' (a statistical function) cannot be claimed, even if such may appear to exist.

I take Gisele's word for the existence as she stated it. This comes from observations and a lot of tedious painstaking work sampling and testing, not a formula, a statistical probability calculation.

Ahh.... no, I think the word graphics may have been a bit fuzzy around the edges, causing loss of focus?

If you were to trace a map of human

but, I guess, they don't. Maybe there is a problem with the model. What about if the migratory direction was reversed and a homo sapient Adam met a non-quite homo sapient Eve like Wolpoff seems to suggest?

Regards.

Ah, now I understand what you are saying! I think anyway. You are of course correct that a 'change' in the mtDNA has absolutely nothing to do with a 'change' in the Y-chromosome. In fact that independence is what I would be counting on in my little idea.

Just hypothetically now, lets assume that a given train of mtDNA changes leads one to believe that there was a trail of 'Caucasian' mtDNA moving east to west across central Asia. For example lets just hypothesize that this was the Scythian migration westward. This would be defined by a series of 'commonalities' where for example Finns turned up with mtDNA that could logically have only originated in the area of central Asia.

If tracking the Y-chromosome 'commonalities' (which are totally and completely different from the mtDNA indicators), shows the same line of advance, then and only then does the conclusion that the Finns ancestors migrated from central Asia make sense. If the Y-chromosome commonalities only led to the Australian aborigines, well. . . . . you have NOTHING either way just two strange 'just so' findings.

Which is just about what happens in human society I believe. HG males take mates from within the 'tribe' or at least from within neighboring tribes or vice versa depending on the social mores and practices.

OK, you lost me here. Hopefully its explainable by a mutual misunderstanding. 8-)

Drawing a line of inference through one point of even very good data is a very risky thing to do I think. It would take more than a little bit of diligent study to verify or deny that the 'migration map' as traced with mtDNA either agrees or disagrees with the similar map traced with y-chromosome. If by some circumstance they more or less match, then I would suggest that we have proven a very powerful tool to map out ancient migrations. If they disgree in a fundamental sense, I would suggest that we would have debunked a particularly insidious little piece of pseudo-science.

I also trust Gisele's work. While I certainly do not understand all of the details of her findings, Ive got a certain confidence that if she says she found something it is there. I may quibble a bit with the conclusions, but certainly not from the standpoint of worrying about her findings.

Fuzzy is a problem.

Regards

Now THERE is where it gets interesting! Lets just suppose that the two mappings DO disagree!

Just about all of the theories of human evolution hinge around 'humans' originating in one or more locations and then diffusing out across the world. It actually makes no real difference if its one nucleus (in Africa, Asia or whereever), or several (in African AND Asia for example), the concept is that the 'deltas' in either the mtDNA or Y-chromosome would radiate out from these points of origin. Considered seperately, you could probaly produce some sort of 'nearest neighbors' map of this little diasphora using either as a reference.

The trick with parallel but independent data sources is that you increase the crediblilty (statistically) by a huge degree if those two sources agree (call it 'processing gain' for lack of a better term). I have no doubt that most of the research in this area is done by credible scientists trying to work with the data they have and extract the most information possible. That goal in itself, as worthy as it is, just might be the 'problem with the model'!

Not just in Paleoanthropology but in other scientific and technical disciplines, this drive sometimes pushes researchers to see 'under the noise', extracting 'conclusions' when the signal-to-noise ratio (SNR) just does not support it! Let me give you an example from the world of signal processing.

Lets take a transmitted radio signal where the SNR is less than that required to extract the encoded information (<3-6db depending!). No matter what you do to that signal (assuming no preconceived notions on the content and that the offending noise is white noise), you can not extract the intelligence! You may extract SOMETHING from that hissing and poping that you hear, but it is highly unlikely to be the information encoded. Now, lets say you presume that there is another 'channel', on a different frequency, transmitting the same exact intelligence but again at a SNR far too low to extract the intelligence. (in this case, lets imagine that the first signal is mtDNA and the second signal, the Y-chromosome, just to reiterate the 'Tie in'! 8-) )

Lets again think in the RF domain with bad SNR. If I have one tuner set to the first signal and a second receiver tuned to the second I will get two outputs, neither of which is intelligible by itself. With some pretty slick signal processing though, I can add the two signals. However, a very interesting and useful characteristic of 'white noise' is that it is truely statistically random. In other words if I mathematically add two white noise streams I will tend to get a noise reduction function. The encoded information on the other hand is decidedly non-random adding that portion of the two signalsl tends to increase the modulated component of the signal's power by 3db! So, noise starts cancelling itself and the signal starts increasing in raw power. Now, if I add in enough separate and independent channels, suddenly the SNR is not quite so disadvantageous! 8-) (If you are interested in a more detailed and technically rigorous discussion, google up some of the theory behind 'spread spectrum'.)

In this example, mtDNA and y-chromosome both have the potential to carry the 'bread crumbs' that might be useful for tracing uncharted human migrations. With either, standing alone, I have to wonder mightily about the SNR. Others probably worry more about the viability of their pet theories (and maybe even theses) extracted from the hissing and popping of that one single, noisy mtDNA channel. 8-)

Regards

'humans' originating in one or more locations and then diffusing out across the world.

In other words, the current approach limits its horizon to the Homo Sapiens Sapiens gene pool.

would radiate out from these points of origin.

But what about if the current gene pool were to contain pre-Homo Sapiens Sapiens strains (strains of populations that were not the first to reach the Homo Sapiens Sapiens threshold)? In that case, obviously, the 'deltas' would not match.

disciplines, this drive sometimes pushes researchers to see 'under the noise', extracting 'conclusions' when the signal-to-noise ratio (SNR) just does not support it!

'Drives' and, in anthropology, I would add, big ideological agendas.

Regards

Robert Call