map illustrates the first principal component (PC) of molecular
genetic variation in Europe, suggesting demic diffusion from
Antolia, probably associated with the spread of farming. The
range between the maximum and the minimum values of the PC has
been divided into eight equal classes, which are indicated by
different intensities of shading. The direction of increase
of PC values is arbitrary.
Cavalli-Sforza et al. 1994: 192, reproduced by permission of
the authors and Princetown University Press.