The sickle cell gene's recent introgression into East Africa

This is a "Short Report" and it is indeed very short! It seems like they assume that patterns of mt-DNA and Y-chromosome diversity are not subject to forces of selection and just represent neutral "population-level forces". I wonder how safe this assumption is? Here is the basis of their test:

By typing both the haploid Y chromosome and the S gene in the same samples it should be possible to test for common demography as well as detect affinities of particular S variants observed in Sudan to other regions of Africa.

their conclusion:

Our results suggest that the sickle cell gene may have been preferentially introduced through males of migrating west African tribes (Figure 1), particularly Hausa-Fulani, and Bagara in the large migrations that began in the eighteenth century and escalated during the nineteenth and early twentieth century. The estimates of a recent figure of 1–3 generations for the introduction of the gene and associated haplotypes to eastern Sahel, is consistent with demography during the past 100 years and with a hypothesis of a recent origin of malaria as a major human infection.

"recent origin of malaria as a major human infection" - hmm...interesting!

Co-introgression of Y-chromosome haplogroups and the sickle cell gene across Africa's Sahel

Rihab E Bereir, Hisham Y Hassan, Niven A Salih, Peter A Underhill, Luigi L Cavalli-Sforza, Ayman A Hussain, Dominic Kwiatkowski and Muntaser E Ibrahim

European Journal of Human Genetics (2007) 15, 1183–1185;

Abstract: The Sahel that extends from the Atlantic Ocean to the Ethiopian highland is a historical reservoir of Africa's cultures and grandest populations and a known arena of ancient and recent migrations. We are interested in the issue whether such migrations were also carriers of genetic traits and whether this introgression could be associated with population genetic markers. Based on analysis of Y-chromosome haplogroups, we present evidence that the sickle gene, one of the major protective polymorphisms known in malaria, has in fact found its way only recently to the gene pool of the populations in eastern Sahel. We discuss the possible dynamics of the process and give estimates of the age of the introduction of the S allele into eastern Sahel.