In its original formulation, the demic diffusion model includes three phases: (1) population growth, prompted by new available resources as in the case of early farmers, and/or other technological developments; (2) a dispersal into regions with lower population density; (3) a limited initial admixture[clarification needed] with the people encountered in the process.
Evidence
Theoretical work by Cavalli-Sforza showed that if admixture between expanding farmers and previously-resident groups of hunters and gatherers was not immediate, the process would result in the establishment of broad genetic gradients. Because broad gradients, spanning much of Europe from southeast to northwest, were identified in empirical genetic studies by Cavalli-Sforza,
Robert R. Sokal,
Guido Barbujani,
Lounès Chikhi and others, it seemed likely that the spread of agriculture into Europe occurred by the expansion and the spread of agriculturists, who possibly originated in the
Fertile Crescent of the
Near East.[2] That is referred to as the Neolithic demic diffusion model.
^Chicki, L; Nichols, RA; Barbujani, G; Beaumont, MA. 2002. Y genetic data support the Neolithic demic diffusion model. Proc. Natl. Acad. Sci. 99(17): 11008-11013.
^C. Loring Brace, Noriko Seguchi, Conrad B. Quintyn, Sherry C. Fox, A. Russell Nelson, Sotiris K. Manolis, and Pan Qifeng, "The questionable contribution of the Neolithic and the Bronze Age to European craniofacial form," in
Proceedings of the National Academy of Sciences of the United States (Jan. 3, 2006). Vol. 103, No. 1, pp. 242-247.
[1]doi:
10.1073/pnas.0509801102
^M. Zvelebil, in Hunters in Transition: Mesolithic Societies and the Transition to Farming, M. Zvelebil (editor), Cambridge University Press: Cambridge, UK (1986) pp. 5-15, 167–188.
^P. Bellwood, First Farmers: The Origins of Agricultural Societies, Blackwell: Malden, MA (2005).
^M. Dokládal, J. Brožek, Curr. Anthropol. 2 (1961) pp. 455–477.
^O. Bar-Yosef, Evol. Anthropol. 6 (1998) pp. 159–177.