Holocene human migrations in Africa: a male perspective

Early Holocene was characterised by a worldwide climatic amelioration (12-5 kya), which led to the formation of the Green Sahara in Africa. In a previous project, in order to understand the effects of this fertile environment in the peopling of Africa, we deep-sequenced ~ 3.3 Mb in 104 Y chromosomes belonging to four trans-Saharan haplogroups and identified 5,966 mutations. By genotyping 142 selected markers in 7,955 males from 145 populations, we found several pieces of evidence about the role of the Green Sahara, but also footprints of other demographic events occurred outside the Sahara. In particular, we found clues of ancient trans-Mediterran ean contacts (8-7 kya) between Africa and southern Europe. In the Sahel, we identified a sub-clade, which is common among different Fulbe groups and can be informative about the history of this enigmatic population, whereas the phylogeography of other sub-lineages suggest ed movements along the Sahelian belt occurred 6-5 kya and possibly linked to the spread of the Nilo-Saharan languages. In the Horn of Africa, we found different specific lineages, suggestive of local demographic expansions occurred ~ 5 kya. Finally, framing the data in a wider context, we were able to gain more information about the trans-Atlantic slave trade (15th-19th centuries) and the Arab slave trade (7th- 9 th centuries ), which seems not to have been the major determinant of the sub-Sah aran genetic component in northern Africa, at odds with previous hypotheses.