Modeling the contrasting Neolithic male lineage expansions in Europe and Africa

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Modeling the contrasting Neolithic male lineage expansions in Europe and Africa

Michael J Sikora, Vincenza Colonna, Yali Xue, Chris Tyler-Smith
Investigative Genetics 2013, 4:25 doi:10.1186/2041-2223-4-25

Background
Patterns of genetic variation in a population carry information about the prehistory of the
population, and for the human Y chromosome an especially informative phylogenetic tree has
previously been constructed from fully-sequenced chromosomes. This revealed contrasting
bifurcating and starlike phylogenies for the major lineages associated with the Neolithic
expansions in sub-Saharan Africa and Western Europe, respectively.
Results
We used coalescent simulations to investigate the range of demographic models most likely
to produce the phylogenetic structures observed in Africa and Europe, assessing the starting
and ending genetic effective population sizes, duration of the expansion, and time when
expansion ended. The best-fitting models in Africa and Europe are very different. In Africa,
the expansion took about 12 thousand years, ending very recently; it started from
approximately 40 men and numbers expanded approximately 50-fold. In Europe, the
expansion was much more rapid, taking only a few generations and occurring as soon as the
major R1b lineage entered Europe; it started from just one to three men, whose numbers
expanded more than a thousandfold.
Conclusions
Although highly simplified, the demographic model we have used captures key elements of
the differences between the male Neolithic expansions in Africa and Europe, and is consistent
with archaeological findings.

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