The MAJOR PN2 CLADES - E3a and E3b haplogroups: Investigating the backdrop against which they came about.
Recently, it has been proposed that E3b originated in sub-Saharan Africa and expanded into the Near East and northern Africa at the end of the Pleistocene (Underhill et al. 2001). - Cruciani et al. 2004, Phylogeographic analysis of haplogroup E3b...
We hear much about E3b and E3a haplogroup bearing populations in Africa, the major haplogroups on the African landscape today, but when and where did these lineages likely come about?
Here is what the present author of the blog thinks occurred, based on the information available to the author:
Between 23 and 18ky ago—Ogolian period begins, which coincides with and is likely connected to the LGM weather situation.
23,000 BP ~ 21,050 BC: "After a favourable climatic period, characterised by relatively dense and diversified Palaeolithic occupations, the arid Ogolian begins locally around 23000 years BP and is represented at Ounjougou by a significant depositional and archaeological hiatus." — Aziz Ballouche [see: Link ]
—Much of North Africa and the Sahara are characterized by adverse weather conditions, with much of the region turning arid. The Sahara at this time, extends south beyond its current boundaries to a certain point, possibly a little beyond the Niger bend.
Arid conditions extend all the way to the "horn" coast of the African Horn region, possibly encouraging populations to reside more inwards—away from that horn-shaped coastal region; rather, likely towards the region straddling southern Sudan, Ethiopia, Kenya and Uganda or even further—region straddling Uganda, Kenya, and Tanzania.
—PN2 clade (E3) bearers in the vicinity of the Sudanese-Central African Republic -Ugandan-Kenyan region give rise to E3a ~ between 21 and 18 ky ago [pending additional or new info]; E3b-M35* would have likely arose relatively earlier than E3a* [as evidenced by its near absence in some the populations that carry this], sometime prior to the Ogolian and the LGM period. At this time, it was likely the M78 derivative that came about ~ between 19 and 15 ky ago. It was also likely during this period, that some E3b-M35 variants spilled over to the "southwest Asia", which would be identified as E-M34. The E-M78* likely arose somewhere in the bidirectional-migration route between Northeast and sub-Saharan East Africa; this location was likely in the region straddling upper Egypt and Sudan of the eastern Sahara, amongst earlier E-M35 migrants from sub-Saharan East Africa. These M78 bearers were increasingly pressured to move further south due to progressive aridity, possibly as far as Uganda-Kenya and/or Tanzanian general region.
—The E3a bearing group would proceed westward, perhaps meeting groups of earlier lineages at the Shum Laka region of Cameroon, whereby quartz micro-lithic culture had already been in place by around 30 ky ago, hence preceding the rise of E3a common recent ancestor. But this group wouldn’t stay put here, at least not every section of it; they’d proceed to the savanna, grassland or vegetation holdouts in West Africa beyond the then boundaries of the Sahara. This probably occurred some time between 15ky and 13ky ago. During this period, as the Saharan aridity began to gradually slacken, some E-M78 bearing proto-Afrasan speaking nomads likely made their way into the Levant via the Sinai corridor.
Others taking refuge in the Cameroonian savanna-tropical forest general region probably followed suit, that is—after the aforementioned initial batch of migrants [bearing E3a descendants]; or else, the same group of people [from the initial migrants] shifted locations along the west African vegetation belts, once it became apparent that the far western reaches didn’t have much to offer, but the water system [as part of the Niger River]—however relatively shallow or what not—offered something additional. Finally, when the conditions in the Sahara were turning around for the better, starting between ~ 12ky and 11ky ago, these migrants would proceed northward, leaving the sort of trails that find expression at Ounjougou—Mali.
10th millennium BC ~ 12ky ago: At Ounjougou—"It is not until the Holocene and the return of humid climatic conditions, beginning in the 10th millennium BC, that it is possible to again observe evidence of human occupation." — Aziz Ballouche [see: Link ]
"Consequently, it has to be seen in the context of heavy rainfalls and a resettlement of the vegetation cover, during the 10th millennium BC, that a new population arrives on the Plateau of Bandiagara." — Human population and paleoenvironment in West Africa [see: Link ]
From 30,600 to 10,000 BC: "A cultural flow, from the southeast of Subsaharan Africa and to the Sahara, could explain the diffusion of the microlithic industries all the way through West Africa. We observe them initially in Cameroon at Shum Laka (30.600-29.000 BC), then at the Ivory Coast in Bingerville (14.100-13.400 BC), in Nigeria in Iwo Eleru (11.460-11.050 BC), and finally in Ounjougou (phase 1, 10th millennium BC)." — Human population and paleoenvironment in West Africa [see: Link ]
It's very probable that this E3a bearing group(s) came into contact with the then wandering earlier-inhabitants of west Africa, who would have been pressured to move southward beyond the then Saharan desert boundaries, due to progressing aridity of the Ogolian period. These groups could have brought their central-Saharan pottery [e.g. found in Niger] traditions with them [developed perhaps sometime during the transitioning period to the wetter phase of the Sahara], just as the E3a bearing group(s) brought the microlithic traditions that they possibly picked up in the vicinity of the Shum Laka region [see above excerpt carbon dating estimations of finds] …and/or else…the new migrants produced their own versions of pottery in their new found location [as it is not noted whether these pottery had affinities with examples found in the aforementioned central Saharan region], at a time when it was trendy to carry stuff in pottery ware in the Saharan-Sahelian zone, with the filling up river systems due to the Monsoon rains.
The 10,000 and 9,000 BC (Phase 1 of the Holocene in Ounjougou): "The first sedimentary sequence of the Holocene can be observed at the Ravin de la Mouche. It's a channel dug into yellow Pleistocene silt and filled with coarse grained sand and pebbles. As a chronological reference for the upper levels of this early Holocene site, we hold ten radiocarbon dates between 9400 and 8400 BC cal. The associated lithic industry evidences predominantly a unidirectional mode of debitage. But also other technologies, such as bipolar on anvil or multidirectional, have been applied by the Early Holocene population. The raw material mainly used was quartz. The typological range consists of small retouched flakes, geometric microliths and perçoirs, but also of continuously retouched bifacial arrowheads and backed points." — Human population and paleoenvironment in West Africa [see: Link]
"By" 11,000 years BP ~ by 9050 BC:
"The age of the sediment in which they were found suggests that the six ceramic fragments discovered between 2002 and 2005 are at least 11,400 years old. Most ancient ceramics from the Middle East and the central and eastern Sahara regions are 10,000 and between 9-10,000 years old, respectively." — Human population and paleoenvironment in West Africa [see: Link]
By the 'beginning' of 8,000 BC: "Outstandingly, there has been evidence of the presence of pottery and seed grinding implements since at least the beginning of the 8th millennium BC. It is therefore the oldest site. The eighth millennium (Phase 2 of the Holocene in Ounjougou) known of this socio-economic type in sub-Saharan Africa...
The pottery and the seed grinding implements of phase 2 of Ounjougou are the oldest artefacts of this type known at present in sub-Saharan Africa. To current knowledge, the pottery of Ounjougou could either have been invented in the actual Sudano-Sahelian zone or been imported from the Central Sahara, where there has been evidence since the ninth millennium BC. Still, the oldest pottery known in the Sahara, from the site of Tagalagal in Niger, is already quite diversified at the moment of its appearance, possibly meaning that the technique has been introduced.
The lithic industry of the phases 1 and 2 on the other hand shows similarities to both more southern and Saharan industries. Quartz microliths, obtained through bipolar debitage on anvil, are a characteristic of the West African techno-complex according to Kevin MacDonald. Bifacially retouched arrowheads, in contrast, are specific for Saharan production." — Human population and paleoenvironment in West Africa [see: Link]
"The eighth millennium (Phase 2 of the Holocene in Ounjougou): The subsequent Holocene sequence is well documented by two principal sites, the Ravin du Hibou and Damatoumou. The archaeological levels can be quite clearly chronologically placed by means of a date obtained through OSL measurements (9420±410 Ka) and seven radiocarbon dates (between 8000 and 7000 BC cal). The lithic industry, exclusively quartz, is characterised by unidirectional, bidirectional and peripheral debitage, as well as by bipolar on anvil. There are essentially microlithic tools: perçoirs, backed points, notched pieces, denticulates, scrapers, retouched flakes and geometric microliths. Some small bifacially retouched arrowheads were also found on those sites. At the Ravin du Hibou, seven sherds have been found during excavation. They are heavily fragmented and thus preventing the reconstruction of the form of the vessel. Quartz has always been used as a temper. In just a single case, grog has been used in addition. Two shards show identifiable decorations. Two different techniques have been used: A rolled impression, possibly made with a peigne fileté souple or with a cordelette, and a simple comb impression. There were also seed grinding implements discovered at the Ravin du Hibou, a fragment of a seed grinding stone and a cylindrical upper grinding stone." — Human population and paleoenvironment in West Africa [see: Link]
On the DNA side:
If we look at the samplings undertaken thus far, the west African populations on Atlantic-bordering west coasts—like the Senegalese samples, these groups undoubtedly have amongst the highest frequencies of E3a lineages, but there is something to be discerned: These groups largely carry M2, P1, and M180 lineages devoid of the M191 mutation, perhaps indicating the earlier E3a bearers, while many of the Bantu speaking groups of central, east and southern Africa carry those 191 derivatives:
Although haplotypes 22, 24, and 41 were probably all involved in the Bantu expansion, the processes that determined the current distribution of these haplotypes in the Sudanese belt (a region south of the Sahara extending from western to central Africa) seem to have been more complex and perhaps involved a separate expansion. In particular, haplotype 24 and its derivative, haplotype 22, harbor opposite clinal distributions in the region, a finding that is at odds with the hypothesis of a parallel dispersion of these two lineages in the area.
Haplotype 22 has a frequency of 23% in Cameroon (where it represents 42% of haplotypes carrying the DYS271 mutation), 13% in Burkina Faso (16% of haplotypes carrying the DYS271 mutation) and only 1% in Senegal (Semino et al. 2002), whereas haplotype 24 reaches its highest frequency (81%) in Senegal (Semino et al. 2002).
A possible explanation might be that haplotype 24 chromosomes were already present across the Sudanese belt when the M191 mutation, which defines haplotype 22, arose in central western Africa. Only then would a later demic expansion have brought haplotype 22 chromosomes from central western to western Africa, giving rise to the opposite clinal distributions of haplotypes 22 and 24. — Cruciani et al. 2002
The above suggests that the oldest E3a bearing population(s) ultimately moved to the far west corner of the continent.
From Semino et al. 2004, we have:
It is also of interest, that the Senegalese samples have higher E3* frequency, which attains its highest frequency in Ethiopian populations, than the Bantu speaking groups, where the only group tested positive, was that of the South African Bantu sample:
Bantu (South Africa) - E3* = 1.9%, Senegalese - E3* = 2.9%, Ethiopian (Amhara) - E3* = 10.4%, Ethiopian (Oromo) - E3* = 12.8% in the ascending order.
The Senegalese sample also bears the E-M.35* lineages:
In descending order…
Ethiopian (Oromo) - E-M35* = 19.2%, KhoiSan (South Africa) - E-M35* = 16.7%, Ethiopian (Amhara) - E-M35* = 10.4%, Berber (North-Central Morocco) - E-M35* = 7.9%, Berber (Southern Morocco) - E-M35* = 7.5%, Senegalese - E-M35* = 5%, Tunisian - E-M35* = 3.4%, Algerian - E-M35* = 3.1%, Arab (Morocco) - E-M35* = 2.3% , Burkina Faso -E-M35* = .9%
E-M78 in descending order….
Arab Morocco = 42.9%, Oromo = 35.9%, Amhara = 22.9%, Sudan =17.5%, Tunisian = 15.5%, Berber (Southern Morocco) = 12.5%, Arab (Morocco) = 11.4%, Berber (Morocco) = 10.9%, Algerian (32) = 6.3%, Berber (north central Morocco) = 1.6%, North Cameroon = 1.3%, Senegalese =.7%
E-M81 in descending order…
Saharawish (North Africa) = 75.9%, Berber (Morocco) = 68.7%, Berber (north central Morocco) = 65.1%, Berber (southern Morocco) = 65%, Algerian = 53.1%, Arab (Morocco) = 52.3%, Arab (Morocco) = 32.6%, Mali = 29.5%, Tunisian = 27.6%, Sudan = 5%, Senegalese = .7%
E-M33 in descending order…
Mali = 34.1%, North Cameroon = 7.9%, Senegalese = 5%, Burkina Faso = 3.8%, Saharawish (North Africa) = 3.4%, Berber (north‐central Morocco) = 3.2%, Sudan = 2.5%, Berber (Morocco) = 1.6%
E-M75 in descending order…
Bantu (South Africa) = 15.1%, Burkina Faso = 11.3%, Khoisan (South Africa) = 4.6%, Sudan = 5%, North Cameroon = 3.3%, Senegalese = 2.9%, Ethiopian (Oromo) = 1.3%
Looking at this data, among predominantly E3a-bearing Niger-Congo language speakers, Senegalese groups have the highest E3* frequency, as well as E-M35*. It follows the North Cameroon sample in this instance, in the E-M78 frequencies - though I’m not sure if those North Cameroon samples comprise of Niger-Congo speaking groups, Nilo-Saharan or some other language phylum group. In west Africa, it succeeds only Mali [and Niger, which wasn‘t included in this sample]—as one of the areas which have considerable Niger-Congo speakers—to have E-M81 bearing candidates, but then, Mali is also well known for its Saharan Tamazight speakers.
In reference to the above, some might look at a lineage as, say E-M78 and imagine it to be a trace of interaction with Saharan or coastal North African Afrasan speaking groups, but microsatellite inspection would indicate otherwise:
It is interesting that both E-P2* and E-M35* and their derivatives, E-M78 and E-M123, exhibit in Ethiopians the 12-repeat allele at the DYS392 microsatellite locus, an allele scarcely seen (Y-Chromosome STR Database), especially [b]in other haplogroups and other populations (A.S.S.-B., unpublished data). In addition, the Ethiopian DYS392-12 allele is usually associated with the unusually short DYS19-11 allele, which is typical of this area. These findings are not easily explained. One possible scenario is that an ancient differentiation of the E-P2 haplogroup occurred in loco (East Africa). However, this also implies a low mutability of the associated microsatellite motif (DYS392-12/DYS19-11). Alternatively, the microsatellite motif may be due to homoplasy.
The first scenario is more likely, since this unique microsatellite haplotype occurs in E-P2*, E-M35*, and E-M78 but is almost absent in all other haplogroups and populations. In addition, the high stability of the DYS392 locus (Brinkmann et al. 1998; Nebel et al. 2001) and of the shorter alleles of DYS19 (Carvalho-Silva et al. 1999) has been reported elsewhere. Moreover, the observation that the derivative E-M78 displays the DYS392-12/DYS19-11 haplotype suggests that it also arose in East Africa. This is illustrated by the microsatellite network (fig. 3, shaded area), which reveals that the Ethiopian branch harboring DYS392-12 is not shared with either Near Eastern or European populations.
The Ethiopian sample may not share the said allele with those populations mentioned, including the northwest African samples as far as I can tell, but it does share the said allele with the Senegalese sample, which would suggest that the Senegalese M78 derivative didn’t come from interaction with its northwest African neighbors; rather, they may well be relics of ancient migrations from east to west.
http://www.journals.uchicago.edu/na101/home/literatum/publisher/uchicago/journals/production/ajhg/2004/74/5/386295/images/medium/fg3.gif Source: Semino et al., Origin, Diffusion, and Differentiation of Y‐Chromosome Haplogroups E and J, 2004.
Some time during post 11ky ago expansions into the wet Sahara, before its return to aridity, with activity going on across the Saharan expanse, like cattle domestication for example, E3a bearers spread well into central-east Sahara. It was likely during this period that HbS mutations were localized, with the oldest E3a bearing groups nearer to the Atlantic-hugging west coasts bearing the Senegalese haplotype, while the Benin haplotype was able to have a more far-reaching expansion northward and northeast ward, due its situation in Niger River Valley vis-à-vis North Africa and the rest of the Sahara.
Additional references to those mentioned in the body of the post:
*Semino et al., Origin, Diffusion, and Differentiation of Y‐Chromosome Haplogroups E and J, 2004.
*Knight et al. 2003 : http://www.bec.ucla.edu/papers/Mountain_3-7-05.pdf
*Cruciani et al. 2004, Phylogeographic analysis of haplogroup E3b.
* Cruciani et al. 2007, Tracing Past Human Male Movements in Northern/Eastern Africa and Western Eurasia: New Clues from Y-chromosomal Haplogroups E-M78 and J-M12.