November 19, 2010

Y chromosomes and mtDNA in Guinea-Bissau

I am not entirely convinced that R1b in this population represents only "European influx". Part of it may be related to the other African R1b.

Forensic Sci Int Genet. 2010 Nov 2. [Epub ahead of print]

Paternal and maternal lineages in Guinea-Bissau population.

Carvalho M, Brito P, Bento AM, Gomes V, Antunes H, Costa HA, Lopes V, Serra A, Balsa F, Andrade L, Anjos MJ, Corte-Real F, Gusmão L.

The aim of the present work was to study the origin of paternal and maternal lineages in Guinea-Bissau population, inferred by phylogeographic analyses of mtDNA and Y chromosome defined haplogroups. To determine the male lineages present in Guinea-Bissau, 33 unrelated males were typed using a PCR-SNaPshot multiplex based method including 24 Y-SNPs, which characterize the main haplogroups in sub-Saharan Africa and Western Europe. In the same samples, 17 Y-STRs (included in the YFiler kit, Applied Biosystems) were additionally typed. The most frequent lineages observed were E1b1a (xE1b1a4,7)-M2 (68%) and E1a-M33 (15%). The European haplogroup R1b1-P25 was represented with a frequency of 12%. The two hypervariable mtDNA regions were sequenced in 79 unrelated individuals from Guinea-Bissau, and haplogroups were classified based on control region motifs using mtDNA manager. A high diversity of haplogroups was determined in our sample being the most frequent haplogroups characteristic of populations from sub-Saharan Africa, namely L2a1 (15%), L3d (13%), L2c (9%), L3e4 (9%), L0a1 (8%), L1b (6%) and L1c1 (6%). None of the typical European haplogroups (H, J and T) were found in the present sample of Guinea-Bissau. From our results, it is possible to confirm that Guinea-Bissau presents a typically West African profile, marked by a high frequency of the Y chromosome haplogroup E1b1a(xE1b1a4,7)-M2 and a high proportion of mtDNA lineages belonging to the sub-Saharan specific sub-clusters L1 to L3 (89%). A small European influx has been also detected, although restricted to the male lineages.



Andrew Oh-Willeke said...

I agree with a possible African origin. The test may not be able to discriminate between R1b-P25 (aka R1b1*) and the principal African version of R1b-V88 (aka R1b1a) which is common, for example, in some North Cameroon peoples who speak Chadic languages and in lower frequencies in other Sahel pastoralists.

A 12% frequency seems too high to be attributable entirely or even mostly to European paternity in Guinea-Bissau. The Portugese presence seems like it was pretty thin until the late 19th century, and other places with comparable colonial legacies don't have that strong of a population genetic signal.

If the analysis was capable of distinguishing R1b1b2 (R-M269) from R1b1* (R-P25), then R-M269 should have made up a little less than half of the sample if it was really derived from Portugese Europeans (which would be the only way it could get to 12%).

A high frequency of R-V88 or its descendants would still be remarkable, however, as all of the substrate languages in Guinea-Bissau are Niger-Congo languages, rather than being Afro-Asiatic (the language family were R-V88 is most common), and is very distant from the places where R-V88 has been found in Niger-Congo language speakers with any frequency. This might be due to a further North latitude in line with the Sahel further inland.

It would be interesting to know if the R1b men were ethnically, religiously, linguistically or regionally distinct from the rest. Intuitively, one would suspect higher African R1b inland, and higher European R1b on the coast.

Andrew Oh-Willeke said...

There is a related article from 2007 with free access. The study found just 2 out of 282 R-P25 men, of whom one was Fulbe (an inland Sahel pastoral ethnicity), and the other was a Bijagos man, which is a coastal island group.

The 2007 paper says this about typing:

"The hierarchical selection of the following 31 Y chromosome binary markers according to the Y Chromosome Consortium phylogeny allowed the inclusion of each Y chromosome into specific haplogroups: YAP, 92R7, SRY4064, SRY10831, P25, PN2, M2, M9, M10, M13, M14, M31, M32, M33, M35, M44, M60, M75, M78, M81, M89, M91, M116, M123, M130, M155, M168, M173, M174 and M191."

Gioiello said...

Having been tested by the YFiler kit, Applied Biosystems, if someone could got the paper, it would be very easy to separate R-M269 from R-V88. Unfortunately the paper isn’t for free.

mcd said...

One consideration is the former Portuguese practice of deporting (Sephardic, and therefore possibly R1b1) Jewish children to their African colonies. This is known to have happened in Sao Tome e Principe, and may also have been the case in Guinea-Bissau. See the sections on both colonies in this Wikipedia article:

Andrew Oh-Willeke said...

The Bijagos have an ancesteral origin in the Sudan in the historic era, also arguing for R1b-V88, rather than a European origin.

Kurika said...

Maybe you are right, but:
- Portuguese rule was thin but constant for more than 550 years; at least 400 before other powers.
- The number of Cabo-verdians was always large (troops and worker´s) and they are half europeans (male side).