A genomic sketch of the Horn of Africa

By Razib Khan | June 9, 2011 7:00 pm


Iman, a Somali model

Since I started up the African Ancestry Project one of the primary sources of interest has been from individuals whose family hail for Northeast Africa. More specifically, the Horn of Africa, Ethiopia, Eritrea, and Somalia. The problem seems to be that 23andMe’s “ancestry painting” algorithm uses West African Yoruba as a reference population, and East Africans are often not well modeled as derivative of West Africans. So, for example, the Nubian individual who I’ve analyzed supposedly comes up to be well over 50% “European” in ancestry painting. Then again, I”m 55-60% “European” as well according that method! So we shouldn’t take these judgments to heart too much. Obviously something was off, and thanks to Genome Bloggers like Dienekes Pontikos we know what the problem was: the populations of the Horn of Africa have almost no distinctive “Bantu” element to connect them with West Africans like the Yoruba. Additionally, a closer inspection shows that the “Eurasian” component present in these populations is very specific as well, almost totally derived from Arabian-like sources. When breaking apart the West Eurasian populations it is no surprise that Northern Europeans and Arabians are among the most distant pairs, even excluding recent Sub-Saharan African admixture. The HapMap Utah European American sample and the Nigerian Yoruba are very suboptimal for people with eastern African background. In contrast, African Americans are a mixture of West Africans and Northern Europeans, so the ancestry painting algorithm has nearly perfect reference populations for them. The results for African Americans may not be very detailed and rich, but they’re probably pretty accurate at the level of grain which they’re offering results.

Though I’m happy to give people of Northeast African ancestry more detailed results than 23andMe, one of my motivations for the African Ancestry Project was to obtain a data set which would allow me to explore the genomic variation in the east of Africa myself. This region is a strong candidate for “source” populations for non-Africans within the last 100,000 years, and, it seems to have experienced rapid population turnover within the last 2,000-3,000 years. My data set is not particularly adequate to my ambitions, yet. But I do now have 5 unrelated Somalis. To my knowledge there hasn’t much exploration of Somali genomics using thick-marker SNP chips, so why not? N = 5 is better than N = 0 in these cases of extreme undersampling.

Before I proceed to methods and results, I want to note that I put up most of my files here. It’s a ~25 MB compressed folder with images, spreadhseets, as well as raw output from ADMIXTURE and EIGENSOFT. I hope readers will take this as an invitation to poke around themselves.


Since my focus was on the Horn of Africa the coverage of populations is relatively constrained compared to what I normally run. From the HapMap I took the Yoruba, Masai, and Luhya. I renamed Masai “Nilotic Kenya” and the Luhya “Bantu Kenya.” The Behar et al. data set has a fair number of Ethiopians, gentiles and Jews. A reader helpfully labelled the various ethnicities by ID. I was going to do that myself, but because this tedious work was done for me I felt much more motivated to produce something instead of putting this task off! From the Behar et al. I also took some Arab populations, as well as Georgians, Lithuanians and Belorussians. I combined the two latter populations into “Baltic.” Syrians and Jordanians were converted to “Levantine” in the bar plots. I left Saudis, Yemenis, and Yemeni Jews disaggregated. Finally, I added some individuals from the AAP: all the people from the Horn of Africa who are unmixed in ancestry, as well as my Nubian individual. In the display that follows AAP members are combined with the ethnic groups which are appropriate in Behar et al.: Oromos, Amharas, and Tigray. Ethiopian Jews (the Beta Israel) I left as is. To mix it up I also brought over the Sandawe from Henn et al. The Somalis are all from AAP. They do not seem related (close relatives generally form their own cluster).

I tried to balance my populations in an ad hoc fashion. I took only ~30 Yoruba, but decided to add in more Masai, because they seemed to be a mixed population rather than a reference, and I wanted to flesh out their variation. I removed individuals who were closely related as per Zack Ajmal’s findings in his review of his reference data sets. After combining the data sets I was left with ~210,000 SNPs, with less than 0.1% missing. I ran this from K = 2 to K = 8 in ADMIXTURE, and, I also generated the top six independent dimensions of genetic variation in EIGENSOFT. I also took the Fst values from ADMIXTURE of the inferred ancestral populations and generated MDS representations of the genetic distances (though the original file can be found in the attached folder).

There are several different types of plots below. The MDS and PCA should be rather straightforward. But a little explanation for the ADMIXTURE bar plots. There are three for every K. First, average results by population. Second, a fine-grained display of all the individuals from all the populations. Third, a fine-grained display of some populations of interest. Please note that in the second set of plots I don’t label all the individuals by population, since it would unreadable. But they go alphabetically, so you should be able to see where populations start, and where they end.

Before I you even look at the results and we discuss them, there is one clear issue which jumps out: there are closely related individuals or clans in the Masai data set which I need to remove in future runs. Though these individuals hogged up higher K’s it didn’t effect the relationships across other populations, so I decided to publish this now before refining it for the future. It’s a learning experience. You can see that these individuals form their own clusters in the MDS and PCA as well. At least the problem reoccurs systematically using different methodologies.

(note: some of the images are larger than shown, so if you want to see better labels for the fine-grained plots, get the image URL and look at it separately)

k3_e
k2_all
k2_all2
k2_e
k3_all
k3_all2
k4_all
k4_all2
k4_e
k4_mds
k5_all
k5_all2
k5_e
k5_mds
k6_all
k6_all2
k6_e
k6_mds
k7_all
k7_all2
k7_e
k7_mds
k8_all
k8_all2
k8_e
k8_mds
pca_2_1
pca_3_2
pca_4_2
pca_5_2
pca_6_2

 

 

The fact that the Masai “break down” at K = 6 is really problematic, as there’s information that’s probably lost here. But several immediate observations:

1) The Somalis, like the Ethiopian groups, show almost no impact from the Bantu expansion. This is contrast to the one Nubian individual, who may have more West African ancestry through intermediate groups, or through direct contact with Bantus who were enslaved and brought to Sudan.

2) When you break apart West Eurasian ancestry the Ethiopian and Somali groups have their contribution almost exclusively from an ancestral component in southern Arabia. This makes some sense because of geography, but when you look at the fractions of “northern” admixture even among Yemeni Jews the proportions are not reflected among the Horn of Africa groups. One hypothesis which is consistent with this might be that the admixture event between the Arabian-like group occurred at a time when south Arabians were more genetically isolated and distinct from populations to the north. I suspect this is almost certainly going to be true before the camel, let alone Islam. Interestingly, just as the Nubian individual has more West African affinities, they also have more European affinities. The Nubian individual’s ancestry is simply more cosmopolitan than that of Ethiopians and Somalis, which is not historically that surprising.

3) There is a rough rank order of admixture estimates. In terms of Africanness it goes from Somali > Oromo > Beta Israel ~ Amhara > Tigray. The sample sizes are small though, so we should be cautious. The Amhara seem to vary the most. One might suspect that the Amhara, being the traditional core ethnicity of Ethiopia of late, assimilated other groups. If you look at the PCA the Somali actually look the most “East African” of the groups on PC 2. Note also the linear pattern of distribution other Ethiopians and the Masai toward Arabians and Bantu respectively. This is suggestive of some sort ancient admixture event between an East African substrate and other populations. I will label this population “Ancestral East Africans” (AEA).

4) The relationship of the Sandawe to the other groups is interesting. It seems clear that the Sandawe are related to the AEA, but are somewhat at a remove. Note that a “Sandawe” component is often found in low proportions outside of the Sandawe across East Africa. While the Ethiopians and Somalis do not have a Bantu aspect to their ancestry, they may have an “Ancestral Sandawe” (AS) one.

I don’t want to say more until I get the Masai data set fixed (and I might make recourse to some of Dienekes’ “tricks,” as well as supervised runs). But overall I would say that the ethnogesis of the Semitic and Cushitic people of the Horn of Africa pre-dates the Bantu expansion. I will do some more playing with this, but they do not seem to generate a “Ethiopian-Somali” cluster so easily as South Asians do. This may be because they are never numerous in any of these analyses. Or, it may be due to the possibility that the admixture event was recent enough that the underlying populations are not as obscured as amongst South Asians. I lean toward the latter, for now. As in South Asia, I do not think that the ethnogenesis of the families of Ethiopian peoples is quite a “one off” admixture event. It is suggestive that you have two major language families, Semitic and Cushitic, in this region.

Image credit: Wikimedia

  • Pingback: Man at Bab el-Mandeb | Gene Expression | Discover Magazine()

  • http://washparkprophet.blogspot.com ohwilleke

    “one Nubian individual, who may have more West African ancestry through intermediate groups, or through direct contact with Bantus who were enslaved and brought to Sudan.”

    Nubia is home to the Kordofani languages, the Easternmost branch of the Niger-Congo languages, in addition to several other language families (and linguists tend to favor a theory that makes this the oldest surviving linguistic layer in Nubia), so an “intermediate group” or slavery isn’t necessary to explain the admixture. It has been a place of exile for successive refugia waves in the Holocene. So, the relatively cosmopolitan mix isn’t surprising either. One can think of Nubia, perhaps, as the multiethnic Switzerland or Caucusas of Africa.

    * * * *

    Semitic, Cushitic and Omoro are all Afro-Asiatic language families. Ethio-Semitic language have been found to have a common ancestor language (lost because it was not written, or at least not written widely), and date from a major superstrate migration into Ethiopia ca. 1500 BCE plus or minus a few centuries. There is considerable debate about where the Afro-Asiatic languages arose and how they are related to each other. The genetic differences between populations speaking different language families in the Afro-Asiatic group do not support a theory of predominantly demic diffusion for the macro-language family as a whole, although individual language families in the Afro-Asiatic macro-language family do appear to have common population genetic origins.

    Time-wise, we know that Coptic (the Afro-Asiatic language of ancient Egypt) was spoken at the dawn of writing ca. 3500 BCE, and that the Semitic language Akkadian (exhaustively documented in the finally complete Assyrian dictionary) was widely spoken and written from ca. 2500 BCE in the North Levant and became to predominant language of Mesopotamia by ca. 2000 BCE. Berbers so genetic population continuity shown in ancient DNA to eras long before the Neolithic in North Africa, so an Afro-Asiatic language wasn’t necessarily their original language.

    The most plausible theory in my view is that Afro-Asiatic went from being a marginal language to a major regional one either in the Egyptian Neolithic or somewhat earlier in the Levantine Neolithic, with each major family (Semitic, Coptic, Berber, Cushitic, Chadic, Omoro) acquiring it by cultural diffusion directly or indirectly from whichever of those language families (probably Coptic or Semitic) was the original Afro-Asiatic language.

    This leaves open a question. What did East Africans speak before the Neolithic? The genetic data seems to disfavor the notion that some language family akin to Niger-Congo of which Kordofani would be a remaining pocket from a once larger geographic reach once stretched all the way to the Indian Ocean. Given that Nilotic also appears to be a relatively recent migrant into the region from the Lake Chad Basin, the Sandawe appear to be the best candidates for closest linguistic and genetic successors to the pre-Neolithic East African hunter-gatherers.

  • Pingback: Flavors of Afro-Asiatic | Gene Expression | Discover Magazine()

  • Pingback: Man at Bab el-Mandeb | Gene Expression | Middleeast News()

  • Eze

    The Amhara seem to vary the most. One might suspect that the Amhara, being the traditional core ethnicity of Ethiopia of late, assimilated other groups.

    The same could also be said of Oromos. There are former Agew (a North-Central Cushitic language which forms the main substratum of the Ethio-Semitic languages) and Amhara regions in upper-central Ethiopia who lost their original languages due to expansionist Borana (a Southeastern branch of Oromos) during the Middle Ages and subsequently became Oromo. This is quite evident in some of the Oromo samples who are very similar to some Amharas, while most seem a bit different. Try to look up the Oromo expansion for more details on this.

    One hypothesis which is consistent with this might be that the admixture event between the Arabian-like group occurred at a time when south Arabians were more genetically isolated and distinct from populations to the north. I suspect this is almost certainly going to be true before the camel, let alone Islam.

    This does seem like a plausible scenario and it would be great if it could be dated.

  • http://forwhattheywereweare.blogspot.com/ Maju

    They have much more “Arab” (West Asian or maybe Semitic) component that I would have expected. If this component is still rather low (20%?) among Cushitic language peoples (Somalis, Oromos), it doubles that figure for Semitic language ones (Amharas, Tigrays). It’s quite impressive, specially considering that flow in the opposite direction (towards Arabia) does almost not show up.

  • Eze

    @Maju

    At K=3 the Yemenite Jews actually show 10% East African, and the Yemenis 16% East African (+11% West African, this latter component seems to be recently introduced though, probably slave-trade related as it generally lacks in the Horn). In the successive K’s the Southwest Asian component ‘eats up’ the East African present in Arabians, but technically it is still there.

  • Pingback: African Ancestry Project: Flavors of Afro-Asiatic()

  • mpc

    interesting. isn’t much of this consistent with known regional origins or migrations of populations, and geographical conditions?

    somali traditions describe their own earliest ancestors as coming from southern arabia and arriving at a time, pre-islam, when all involved were pagans and somalis were sold as slaves in the arab world. (and couldn’t these early southern arabians be remnants of bands of groups of early o.o.a. migrants, maybe back-migrants, who went on to settle that part of the peninsula and west asia?) also, waves of semitic folks from across arabia, including relatively few jewish mirgants who later converted locals, invaded or lived and traded in pre-christian ethiopia/eritrea.

    both of these histories unfolded, at the earliest, millennia before bantu migrations completely skirting the horn because it was high and dry at a time when bantu farmers and herders were heading southeast toward the fertile kenyan highlands and tanzania. there, they bumped into southern cushitic and nilotic (nubian?) migrants from the north, among others. but bantus never entered northeastern africa. does anyone claim that they ever did or intended to?

    the sandawe angle is interesting here for the same reason it’s generally compelling to most of us: the a.e.a. angle. is the idea that some pre-historic peoples related to/descended from the sandawe either were the proto-somalis with whom southern arabians mixed, or were already admixed with these proto-somalis when southern arabians who somehow jump-started somali identity arrived? i’ve read or heard that, pre-historically, some kind of once nomadic bushman (proto-san/sandawe/khoisan?) populated up to 60% of eastern and southern africa. it is possible that they lived in the horn too, or that conditions led to their mixing with neighboring inhabitants of northeastern africa.

  • mpc

    after posing the above questions, i re-checked my afram father’s str-country matches. he has the following curious matches:

    1 E1b1a8 2-step mutation match in yemen;

    1 E1b1a 3-step mutation match in ethiopia;

    and 1 E1b1a 4-step mutation match in somalia.

    he also has 1- and 4-step mutation matches in saudi arabia (arabs).

    he’s typical E1b1a8a1a, so i don’t know what these matches mean, if anything, about bantu/west african connections with the horn.

  • Eze

    somali traditions describe their own earliest ancestors as coming from southern arabia and arriving at a time, pre-islam, when all involved were pagans and somalis were sold as slaves in the arab world. (and couldn’t these early southern arabians be remnants of bands of groups of early o.o.a. migrants, maybe back-migrants, who went on to settle that part of the peninsula and west asia?)

    Most Somalis do not claim Arabian origins, only in recent times did such myths arose, mainly because of the spread of Islam many Muslim cultures around the world tried to link themselves to prophet Muhammad’s tribe (Quraysh). Most of the Somali Y-Chromosome lineages trace back to Upper Egypt/Nubia (read about E-V12) rather than Arabia. The second most common Somali patrilineage T-M70 is associated to have spread from the Levant through the Nile corridor rather than Arabia as well. Maternally we do find more evidence of Arabian admixture, mainly through lineages like N1a, R0, I, X, Hv1.

    Ethnic Somalis (that is those of Cushitic origin) were never sold into the Arab world as slaves. Most ports where slaves were shipped out of in Somalia were in the coastal south of the country where they exported Bantus. The southern coastal stretch of Somalia was part of the Swahili Empire and had little to do with the rest of the country until very recently. Dialects of Swahili are still spoken in this region. Most Middle Easterners who have above average African admixture tend to have high West African admixture (through Bantus) rather than high Horn African admixture. If you look at the genetic charts posted above you can see that West African/Bantu admixture is very low to non-existent in ethnic Somalis, while it is often found in Middle Easterners with recent African admixture.

    after posing the above questions, i re-checked my afram father’s str-country matches. he has the following curious matches:

    E-M2 has a very low frequency in these regions, and is in East Africa associated with the Bantu expansion rather than suggesting it originated there.

  • mpc

    even more interesting. guess some of those old arab historians and the brits citing them were just confused.

    also not suggesting any east african origins by those few paternal matches; no investment in any of that or tidy lines of ancestry. but the suggested bantu expansion does muck things up a little. and btw what are “somali bantus”?

  • Eze

    btw what are “somali bantus”?

    The Somali Bantu are a minority ethnic group in Somalia (making up around 10% of the population). They primarily reside in southern Somalia, near the Juba and Shabelle rivers, and are the descendants of people from various Bantu ethnic groups who were brought over from what is now modern-day Malawi and Mozambique by Arab merchants through the Swahili Coast trade network.

    In Somalia there are three main groups, ethnic Somalis with native Horn African origins who form the vast majority, Bantus, and the Benadiri who are of recent Persian-Arab origin.

  • Lee

    Great work Razb!

    You may be interested in the study below by Kidd et al. from earlier this year. It analyses 128 Ancestry Informative Markers (AIM) in various global populations, and includes both Somali and Ethiopian Jew samples:

    http://medicine.yale.edu/labs/kidd/498.pdf

    The Somali sample in that study at K=2 turned up roughly 50% Eurasian, not far outside the Mozabite range, with said non-Sub-Saharan component largely tracing back to Middle Eastern groups (it was especially appreciable in Kuwaitis). Unexpectedly, the Ethiopian Jew sample’s Eurasian component averaged out at only about 25%, comparable to a Maasai sample and the Sandawe.

    Of course, only limited inferences can be drawn from this data given the low number of AIMs analysed. It’s well below Bauchet et al. (2007)’s recommended 1,200 AIM minimum. Per Galanter et al. (2010), among others, the analysis of a small number of markers in admixed populations tends to significantly overestimate the minor ancestral component while underestimating the major ancestral component:

    http://www.ashg.org/cgi-bin/2010/ashg10s?author=galanter&sort=ptimes&sbutton=Detail&absno=22642&sid=75534

    http://img34.imageshack.us/img34/9231/bauchetaims.png

    Despite this, the Kidd et al. study still shows a substantial Eurasian component in the Somali sample, suggesting that said non-Sub-Saharan element probably would’ve appeared even higher had more markers been analysed. Overall, it seems to be consistent with your findings above.

    I also wanted to draw your attention to some ethnological work, which suggests that many modern Oromo-speaking peoples are of assimilated Omotic origin and that the southern or ‘Sab’ Somalis have an appreciable Sub-Saharan component brought on by admixture, well over and above the norm for the Somali population as a whole:

    http://books.google.ca/books?id=xmp2lsKlqx0C&pg=PA252#v=onepage&q&f=false

    http://books.google.ca/books?id=2Nu918tYMB8C&pg=PA8#v=onepage&q&f=false

    Given the foregoing, perhaps it would be better in future, if possible, to consider further dividing the Oromo, Somali and other Horn populations into sub-ethnic or at least geographical groups where and when ethnological and historical data warrants it, as Froment (1999) and other studies have done, often to illuminating results (e.g. southern Oromos vs. central Oromos, southern Somalis vs. northern Somalis, sort of similar to Upper Egyptians vs. Lower Egyptians). I’m certain that the various ancestral population elements captured in such comparative admixture analyses will show markedly different proportions (if not vary altogether) between said sub-ethnicities, as they consistently have in numerous other bio-anthropological studies.

  • http://blogs.discovermagazine.com/gnxp Razib Khan

    tx! i appreciate the ethnological detail.

  • Eze

    @Lee,

    The Oromo in these experiments were sampled in Addis Ababa and in the Borana regions of Ethiopia. This was confirmed by correspondence with Doron Behar. The Somali participants from 23andMe are from various parts of the country (mainly Northern and Central ones but also one Southerner), the difference in ‘Eurasian affinity’ between them is negligible (2% at best). Somalis are fairly homogeneous and only recently admixed individuals with either Bantus or Arabs would deviate from these results while most would come out fairly similar.

  • Lee

    Eze: I respectfully disagree. Oromos and Somalis are in no way homogenous, primarily due to assimilation of and admixture with foreign peoples in certain segments of their respective communities. This isn’t haphazard either but varies in a relatively consistent fashion according to clan status (i.e. ‘noble’ vs. ‘subordinate’) and/or geographical location, both of which often overlap. They even have specific names for the assimilated and admixed peoples and groups in their respective caste systems. This has also been fairly well-documented in their own oral and written histories, those of neighboring peoples, as well as in ethnological and anthropological work.

    http://books.google.ca/books?id=W5T-3ORUbegC&pg=PA109#v=onepage&q&f=false

    http://books.google.ca/books?id=ra89AAAAIAAJ&pg=PA129#v=onepage&q&f=false

    Besides the links above and in my earlier post, I also refer you to Froment (1999). Note the disparate location of the southern Somali or ‘Sab’ sample vis-a-vis the northern (or ‘noble’) Somali sample in the diagram below:

    http://i52.tinypic.com/i72808.jpg

    Razib: Anytime. You might also be interested in G. Billy’s study below (it’s in French though), especially its Figure 2. It examines cranial variation among various Afro-Asiatic, Bantu and Nilo-Saharan-speaking populations in Northeast Africa, Southwest Asia and the Great Lakes region, sort of like an osteological parallel to what you are attempting here with genetics. The paper illustrates some of that intra-ethnic biological diversity one sees in the Oromo and Somali groups, in particular, and also seems to support your findings regarding the possible Middle Eastern derivation of the ancestral Eurasian component in many Horn African populations:

    http://www.persee.fr/articleAsPDF/bmsap_0037-8984_1988_num_5_1_1662/article_bmsap_0037-8984_1988_num_5_1_1662.pdf

    From this and other studies, these Eurasian affinities would appear to be generally greater in the northern Horn groups as opposed to the more southerly Horn groups (at least the ones of long-standing), which makes sense given the former’s generally closer geographical position relative to North Africa and Western Asia.

  • http://washparkprophet.blogspot.com ohwilleke

    “Most of the Somali Y-Chromosome lineages trace back to Upper Egypt/Nubia (read about E-V12) rather than Arabia. The second most common Somali patrilineage T-M70 is associated to have spread from the Levant through the Nile corridor rather than Arabia as well. ”

    This statement, to the extent accurate, would suggest a scenario in which the Cushitic languages (at least) and perhaps Omoro languages as well, are likely to be genetically derivative of Coptic (or less likely Semitic), which pushes a place of origin for the Afro-Asiatic languages to the Nile or Levant, and pretty much out of sub-Saharan Africa.

    While this makes sense from a perspective of major language families tracking the path of the diffusion of food production technology during the Neolithic or later, I haven’t seen anyone make a really definitive claim that there is population genetic evidence for this Cushitic language origin or for that event having a strong demic component in published journal articles.

    Also, this scenario seems to suggest a route tracking the Nile to its Blue Nile source and then a bit beyond, rather than a Red Sea maritime trade origin for the Somalis.

    Do you know if there is evidence of archaeological cultures in Horn Africa that shows with Egyptian influences that show discontinuties from prior cultures at the onset of food production from domesticed plants and animals in Horn Africa? Most of the media reports of digs in the region seem to pertain to the modern human evolution era rather than the Holocene.

    I’d also be curious to know if what your take is on the population genetics of Chadic language speakers, the other major sub-Saharan Afro-Asiatic linguistic family. One could see them as parallel to the Cushitic founding group, following the White Nile to its source and a bit beyond into the Chad River Basin (or from the Nile via a wet sahara lake chain from it to Lake Chad that no longer exists) rather than the Blue Nile. But, the population genetics that I’ve seen have been patchy enough to make conclusions difficult to reach on this point.

    A conclusion that Chadic population genetics, in addition to Cushitic population genetics have origins in Egypt or points North would have major implicitation for the pre-history of the Afro-Asiatic languages and the relationships of the major Afro-Asiatic language families to each other.

  • Eze

    @Lee,
    I do not disagree that the Oromo are quite heterogeneous; Razib’s data shows this as well if you look at the individual results. It is most likely caused by the various Oromo expansions into upper-central Ethiopia.

    However, I do not see any evidence yet that there is a stark difference in extra-African ancestry between North and South Somalis on the genome-wide level. This is primarily based on the Somali samples collected in the African Ancestry Project, which is the best we have so far. They are from geographically distant places yet come out pretty much the same. This to me signals that the general Somali population is very homogeneous. I guess there is a lot of truth to Somalia often being described as the most homogeneous African nation.

  • Eze

    @ohwilleke,
    ”This statement, to the extent accurate, would suggest a scenario in which the Cushitic languages (at least) and perhaps Omoro languages as well, are likely to be genetically derivative of Coptic (or less likely Semitic), which pushes a place of origin for the Afro-Asiatic languages to the Nile or Levant, and pretty much out of sub-Saharan Africa.”

    Hmm…Whether Egypt or the Horn of Africa, I’m not sure it matters that much, to be honest with you. Either way, it was roughly that region of the world, separated by very little. This is nearly like arguing if a haplogroup developed in Northern China or Mongolia.

    ”Do you know if there is evidence of archaeological cultures in Horn Africa that shows with Egyptian influences that show discontinuities from prior cultures at the onset of food production from domesticed plants and animals in Horn Africa? Most of the media reports of digs in the region seem to pertain to the modern human evolution era rather than the Holocene.”

    I am not too well versed in the archaeological finds in this region, but as you said most digs there do indeed pertain to AMH evolution. Even the archaeological evidence of traces of the Land of Punt in the Horn is marginal.

    ”I’d also be curious to know if what your take is on the population genetics of Chadic language speakers, the other major sub-Saharan Afro-Asiatic linguistic family. One could see them as parallel to the Cushitic founding group, following the White Nile to its source and a bit beyond into the Chad River Basin (or from the Nile via a wet sahara lake chain from it to Lake Chad that no longer exists) rather than the Blue Nile. But, the population genetics that I’ve seen have been patchy enough to make conclusions difficult to reach on this point.”

    Chadic speakers are quite diverse; the Nigerian Hausa are only marginally different from the Yoruba and other Niger-Congo populations, while the Mada and other Chadic speakers from the vicinity of Lake Chad have significantly more genetic affinities with East Africans. Most of this affinity seems to be with Nilo-Saharan groups of the Western Sudan. In Tishkoff’s structure runs the Chadic component ‘emerges’ out of the Nilotic component rather than the Cushitic component, this strongly indicates that Chadic groups trace a non-trivial portion of their ancestry further East. If you are interested in Chadic genetics also see this new mtDNA study on Lake Chad populations: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0018682

NEW ON DISCOVER
OPEN
CITIZEN SCIENCE
ADVERTISEMENT

Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!

Gene Expression

This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!

About Razib Khan

I have degrees in biology and biochemistry, a passion for genetics, history, and philosophy, and shrimp is my favorite food. In relation to nationality I'm a American Northwesterner, in politics I'm a reactionary, and as for religion I have none (I'm an atheist). If you want to know more, see the links at http://www.razib.com

ADVERTISEMENT

See More

ADVERTISEMENT

RSS Razib’s Pinboard

Edifying books

Collapse bottom bar
+

Login to your Account

X
E-mail address:
Password:
Remember me
Forgot your password?
No problem. Click here to have it e-mailed to you.

Not Registered Yet?

Register now for FREE. Registration only takes a few minutes to complete. Register now »