K2 represents another migration into Africa

In addition to the ancient back-migration bringing R1*-M173 and mtDNA haplogroups U6 and H into Africa, there appears to be another event during the Paleolithic which brought Eurasians into Africa.

Am. J. Hum. Genet., 74:532-544, 2004

"K2-M70 is believed to have originated in Asia after the emergence of the K-M9 polymorphism (45–30 ky) (Underhill et al. 2001a). As deduced from the collective data (Underhill et al. 2000; Cruciani et al. 2002; Semino et al. 2002; present study), K2-M70 individuals, at some later point, proceeded south to Africa. These chromosomes are seen in relatively high frequencies in Egypt, Oman, Tanzania, Ethiopia, and Morocco and are especially prominent in the Fulbe (18% [Scozzari et al. 1997, 1999]), the highest concentration of this haplogroup found so far."

The puzzle of the formation of modern African diversity is far from solved, including the million-dollar question of the origin and dispersal of the classical Negroids.

A relevant post on the Fulani by David B.