Trading the origin and geographic distribution of an ancestral form of themodern human Y chromosome

We screened a total of 841 Y chromosomes representing 36 human populations of wide geographical distribution for the presence of a Y-specific Alu inse rt (YAP+ chromosomes). The Alu element was found in 77 cases. We tested fiv e biallelic and eight polyallelic markers in 70 out of the 77 YAP+ chromoso mes. We could identify the existence of a hierarchical and chronological st ructuring of ancestral and derived YAP+ lineages giving rise to four haplog roups, 14 subhaplogroups and 60 haplotypes. Moreover, we propose a monophyl etic origin for each one of the YAP+ lineages. Out-of-Africa and out-of-Asi a models have been suggested to explain the origin and evolution of ancestr al and derived YAP+ elements. We analyse the evidence supporting these two hypotheses and we conclude that the information available supports better t he out-of-Africa model.