Origins of Indo-Europeans and the spread of agriculture in Europe: comparison of lexicostatistical and genetic evidence.

A series of tests was undertaken to relate lexicostatistical dissimilarities (LAN) among 48 Indo-European languages to distances representing various causal hypotheses. The comparison is limited to languages currently spoken in Europe. The putative causal distance matrices include (1) geographic (GEO) distances between the languages, (2) distances representing the origin of agriculture (OOA), (3) distances representing a model postulated by C. Renfrew (REN) concerning transformations that gave rise to the major Indo-European language families in Europe, and (4) distances representing a competing hypothesis by M. Gimbutas (GIM) concerning the origin and spread of Indo-European languages in Europe. Pairwise Mantel tests of the matrices show that OOA correlates better with LAN than does REN, supporting Renfrew's basic hypothesis of the dispersal of the Indo-European languages with the spread of agriculture but showing less effect for his postulated transformations. Partial correlation of LAN with OOA when GEO is held constant is significant at p = 0.004, whereas REN is no longer correlated with LAN when GEO is held constant. When repeated for only seven languages chosen to represent the seven major families of Indo-European languages currently spoken in Europe, the results differed appreciably, yielding a negative, albeit nonsignificant, partial correlation between OOA and LAN when GEO is held constant. This apparent contradiction led us to develop some new statistical approaches to examine, confirm, and explain the patterns. Decomposing the Mantel correlation coefficients for the 48 Indo-European languages into several additive correlation components showed that much of the positive component of the correlation coefficient was contributed by LAN, OOA correlation within language families, particularly within the Germanic family, covering up the negative contributions between language families. The differentiation of the seven major Indo-European language branches in Europe seems unrelated to the times of the origin of agriculture. This finding fails to support the fundamental assumption of Renfrew's hypothesis. There are also no significant correlations between LAN and REN or GIM. A series of Monte Carlo experiments confirmed these findings. Consideration of the accumulated evidence from genetics supports the model of demic diffusion during the origin of agriculture. However, published genetic studies and the present study lend no support to the notion that the early farmers were indeed the Indo-Europeans.