Demic diffusion

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Demic diffusion is a demographic term referring to a migratory model developed by Cavalli-Sforza , that consists of population diffusion into and across an area previously uninhabited by that group, possibly, but not necessarily, displacing, replacing, or intermixing with a pre-existing population (e.g. as has been suggested for the spread of agriculture across Neolithic Europe, and what occurred with the European colonization of the Americas).

In its original formulation, the demic diffusion model includes three phases, namely: (1) population growth, prompted by new available resources as in the case of early farmers, and/or by technological developments; (2) a dispersal into regions with lower population density; (3) a limited initial admixture with the people encountered in the process. Theoretical work by Luca Cavalli-Sforza showed that, if admixture between expanding farmers and previously resident groups of hunters and gatherers is not immediate, the process results in the establishment of broad genetic gradients. Because broad gradients spanning much of Europe in the Southeast-Northwest direction were identified in empirical genetic studies by Cavalli-Sforza, Robert R. Sokal, Guido Barbujani, Lounès Chikhi and others, it seems likely that the spread of agriculture into Europe occurred by the expansion and spread of agriculturists, possibly originating in the Fertile crescent of the Near East region. This is referred to as the Neolithic demic diffusion model.

[edit] External links

• Estimating the Impact of Prehistoric Admixture on the Genome of Europeans, Dupanloup et al., 2004
• Origin, Diffusion, and Differentiation of Y-Chromosome Haplogroups E and J: Inferences on the Neolithization of Europe and Later Migratory Events in the Mediterranean Area, 2004
• Y genetic data support the Neolithic demic diffusion model, Chikhi 2002.
• Paleolithic and Neolithic lineages in the European mitochondrial gene pool, Cavalli-Sforza 1997.
• Clines of nuclear DNA markers suggest a largely Neolithic ancestry of the European gene, Chikhi 1997.

[edit] References

1. Chicki, L; Nichols, RA; Barbujani, G; Beaumont, MA. 2002. Y genetic data support the Neolithic demic diffusion model. Proc. Nat. Acad. Sci. 99(17): 11008-11013.