Y chromosome haplogroup E3b

A very important new paper [1] on the phylogeography of haplogroup E3b gives tantalizing new insights into ancient population movements. I had posted before on the subject, but this newer study offers a very detailed view of the geographical structure of this particular haplogroup. Here, I will summarize the findings of this study.

Haplogroup E is found in Africa, Asia and Europe and is divided into three clades:

E1 and E2 are found exclusively in Africa, while E3 is also observed in Europe and western Asia.

E3 is further divided into E3a and E3b, but only E3b is observed in significant frequency in Europe and western Asia in addition to Africa. E3b is an old haplogroup, estimated in [1] to be 25.6 ky old. E3b is defined by the M35 mutation.

E3b can be divided into three subclades E-M78, E-M81 and E-M34 as well as the paragroup E-M34*. All lineages which don't belong in the three subclades are grouped in E-M34*. If two chromosomes belong in the same paragroup, they are not necessarily related to each other: it is possible that the discovery of new mutations will resolve their phylogenetic relationships.

E-M81 is found in NW Africa, not found in sub-Saharan Africa and its frequency sharply decreases eastwards. E-M81 is a "Berber" marker. It is also found in all Iberian populations, signifying Berber admixture, ranging from 1.5% in Northern Italians, 2.2% in Central Italians, 1.6% in southern Spaniards, 3.5% in the French, 4% in the Northern Portuguese, 12.2% in the southern Portuguese and 41.2% in the genetic isolate of the Pasiegos from Cantabria. It is found in only 0.7% of Sicilians and in no southern Italians. It is also not found in the Balkans.

E-M34 is found at low frequencies in Ethiopia, the Near East, Europe and northern Africa. According to the authors, it was introduced into Ethiopia from the Near East. Their justification is that it is found in several populations of the Near East, whereas in eastern Africa it is limited to Ethiopia and not found in Somalia or Kenya. The authors suggest that E-M34 was introduced into Europe in the Neolithic from the Near East, but they caution against this hypothesis, because E-M34 is absent in the Balkans, while it is present in southern-central Europe (6.6% of Sicilians, 2.3% of southern Italians, 3.5% of Sardinians). So, it is either of African origin, or of Neolithic origin in southern-central Europe.

The most important clade is E-M78 and it has an age of 23.2ky very close to the age of the entire E3b haplogroup. It is found in eastern and northern Africa, the NEar East and Europe, where it is most common. E-M78 is divided into four clusters which show a very striking geographical distribution:

Cluster α is found at the highest frequencies in Albania, Rumania and Bulgaria (>20%) and in Greece (according to unpublished data which they cite), and its frequency decreases sharply in all other populations. Surprisingly, it is found outside Europe in frequencies <5%, even in Turkey (3.4%). Thus, the authors conclude that it represents "an important range expansion from the Balkans to western and southern-central Europe". What should be noted is that cluster α Y chromosomes make up almost the entirety of Balkan Y chromosome, are almost entirely absent outside Europe and represent an expansion from the Balkans.

Cluster β is common in northwestern Africa and in Europe it was found in 0.7% of Sicilians and in 1.1% of Sardinians. It has an age of 5.2ky

Cluster γ was found in Cushitic speaking groups of eastern Africa. Its wide distribution as far east as Pakistan suggest that it was involved in the first dispersal of E-M78 chromosomes. It is entirely absent in Europe and the Near East.

Finally, cluster δ is present in all regions at low frequencies. The authors conclude that there was a "relatively great antiquity (14.7+/-2.7ky) for the separation of eastern Africans from the other populations. This cluster is however not found in the Balkans.

Here are the main conclusions of the study:

"In conclusion, we detected the signatures of several distinct processes of migration and/or recurrent gene flow associated with the dispersal of haplogroup E3b lineages. Early events involved the dispersal of E-M78δ chromosomes from eastern Africa into and out of Africa, as well as the introduction of the E-M34 subclade into Africa from the Near East. Later events involved short-range migrations within Africa (E-M78γ and E-V6) and from northern Africa into Europe (E-M81 and E-M78β), as well as an important range expansion from the Balkans to western and southern-central Europe (E-M78α). This latter expansion was the main contributor to the present distribution of E3b chromosomes in Europe."

PS: The study also allows us to quantify sub-Saharan African admixture outside Africa. Most Sub-Saharan Africans belong to E(xE3b), while most non-Africans belong to the E3b clade of the E haplogroup. In Europe, E(xE3b) is found in 4% of the northern Portuguese, 2% of the southern Portuguese and 1.6% of Sardinians. In northern Africa it ranges from 0% in Egyptians to 10% in Mozabite Berbers. In Turkey, it is found only in the Istanbul Turkish sample at 2.9%. In the Near East it is found in 3.6% of Bedouins, 7.3% of the UAE, and 10.3% of Palestinians.

FREQUENCIES

[1] Fulvio Cruciani et al, Phylogeographic Analysis of Haplogroup E3b (E-M215) Y Chromosomes Reveals Multiple Migratory Events Within and Out Of Africa, Am. J. Hum. Genet 74 Link

Posted by Dienekes at March 24, 2004 11:01 PM | PermaLink