Gad et al. 2020

[asante]

Feb 16, 2021 10:13:04 GMT -5 Tukuler al~Takruri said:

Gotta play right


Article| Volume 102, ISSUE 4, P547-556, April 05, 2018




Whole-Genome-Sequence-Based Haplotypes Reveal Single
Origin of the Sickle Allele during the Holocene Wet Phase

Daniel Shriner
Charles N. Rotimi

Open AccessPublished:March 08, 2018DOI:https://doi.org/10.1016/j.ajhg.2018.02.003



Our results provide some suggestions as to where the sickle mutation might have originated. Descendants of the Y
chromosome haplogroup E1b1a-V38 migrated across the Sahara from east to west,⁴⁹ possibly around 19,000 years ago.⁵⁰
E1b1a1-M2 most likely did not originate in eastern or northeastern Africa, but where it originated in either western or central
Africa is unclear.⁴⁹ Accordingly, the sickle mutation most likely did not occur in eastern or northeastern Africa. Our results
indicate that the origin of the sickle mutation was in the middle of the Holocene Wet Phase, or Neolithic Subpluvial, which
lasted from ∼7,500–7,000 BC to ∼3,500–3,000 BC. This time was the most recent of the Green Sahara periods, during
which the Sahara experienced wet and rainy conditions.⁵¹ Our results thus support the Green Sahara as a possible place of
origin of the sickle mutation. An alternative hypothesis is that the sickle allele arose in west-central Africa,¹³, ⁵² possibly in
the northwestern portion of the equatorial rainforest.

Our results also provide some suggestions as to where the three clusters might have originated. Two splits occurred early in
the original βS-carrying population. The first split defined one cluster containing HAP1 and accounting for the Cameroon and
CAR haplotypes. It is plausible that HAP1 was carried from an area in or around present-day Cameroon to the area that is
presently the CAR, as well as to areas east and south, as part of the Bantu expansions. However, the Bantu expansions did
not extend west and north. The second split subsequently separated the clusters containing HAP16 and HAP20, the modal
haplotypes accounting for the Benin and Senegal haplotypes, respectively. HAP16 and HAP20 shared one derived
mutation, consistent with an early split. Furthermore, given the subsequent accumulation of derived mutations not shared
between HAP16 and HAP20, effectively no gene flow occurred between these two descendant populations, consistent with
geographic separation. We therefore hypothesize that the common ancestor of these two clusters existed north of
Cameroon among non-Bantu-speaking peoples in or around present-day Nigeria. From this common ancestral population,
a group of migrants separated and traveled west and north to the area around present-day Senegal and the Gambia. These
migrants could have taken a coastal or an inland route. The finding that the Senegal haplotype was the predominant
haplotype in the sample of Mende from Sierra Leone is consistent with a coastal route. We do not have data to investigate
an inland route, but we note that the frequency of the sickle allele is higher along the coast than inland.⁵³



13. Mears J.G. Lachman H.M. Cabannes R. Amegnizin K.P. Labie D. Nagel R.L.
Sickle gene. Its origin and diffusion from West Africa.
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49. Trombetta B. D’Atanasio E. Massaia A. Ippoliti M. Coppa A. Candilio F. Coia V. Russo G. Dugoujon J.-M. Moral P. et al.
Phylogeographic refinement and large scale genotyping of human Y chromosome haplogroup E provide new insights into the dispersal of early pastoralists in the African continent.
Genome Biol. Evol. 2015; 7: 1940-1950

50. Mallick S. Li H. Lipson M. Mathieson I. Gymrek M. Racimo F. Zhao M. Chennagiri N. Nordenfelt S. Tandon A. et al.
The Simons Genome Diversity Project: 300 genomes from 142 diverse populations.
Nature. 2016; 538: 201-206

51. Castañeda I.S. Mulitza S. Schefuss E. Lopes dos Santos R.A. Sinninghe Damsté J.S. Schouten S.
Wet phases in the Sahara/Sahel region and human migration patterns in North Africa.
Proc. Natl. Acad. Sci. USA. 2009; 106: 20159-20163

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53. Piel F.B. Patil A.P. Howes R.E. Nyangiri O.A. Gething P.W. Williams T.N. Weatherall D.J. Hay S.I.
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Nat. Commun. 2010; 1: 104


=-=


Sudan can be a slippery term, especially The Sudan.
It can and has meant the entire Sahel coast-to-coast
and at the same time the countries Sudan and South
Sudan. The Lake Tchad region is in the central Sudan
aka the northern parts of west-central Africa.

WAM TNA origins of E-M2 proliferation and dispersal
was seen in D'Atanasio2018 data. That Sickle Cell
may also have arose in those times nearby then
Megalake Chad or to its south seems intuitive
and supported by the data.


WAM = West African Monsoon
TNA = Tropical North Africa; roughly 17° - 29° north latitude

True! I would say that based on the earliest occurrence of sickle cell noted in the study to have been in pre-dynastic Kemet, and knowing that the Eastern and Central regions of the Sahara was the primary source of peopling along the Hapi Valley, it would be safe to say that the vicinity of the Sudan (i.e. Northern Chad, Southern Libya) was the likely origin. Further we do not have any evidence of a migration from Western Africa into the Sudan during the Holocene, and certainly not Kemet. We know by following Western academia, that the Niger-Congo language originated in Eastern Africa. This fact correlates with the East African origin of their paternal lineage.  

[zarahan]

Didn't see this 2nd page. But the possible origin of sickle cell if what they say
is true, could be either across the Sahara, or from West-Central Africa. The Benin
Sickle cell variant they locate around the Nigeria-Cameroon zone. If this is the case
then Benin sickle-cell internally might be going north/south. but eternally, outside
West/Central Africa, it might be moving east, across the Green Sahara to touch
north/northeast Africa. In other words the West/Central Africans might have been
bringing that variant (and maybe others) to the Sudan/Egypt area.

This eastward movement would in part explain how Tut and family could end up with ancient
ancestral Great Lakes area (which would include Zambia and Dem Rep Congo region) African
DNA elements. Another alternative track might be northward up into the Saharan
zone then cutting east per map on page 1 above.

Megalake Chad is also another alternative dispersal zone.