Fig. 1.

Visualizing five studies of sickle cell and beta thalassaemia in the Mediterranean. This map summarises data from five studies: (Barnicot et al., 1963; Stamatoyannopoulos and Fessas, 1964; Siniscalco et al., 1966; Cao et al., 2008; Schiliro et al., 1986). Each study recorded the number of beta thalassaemia or sickle cell heterozygotes; we have converted these into allele frequencies, but since homozygotes were excluded from the studies shown these allele frequencies may be a slight underestimate. Supplementary Table S1 provides more information about these data. This map was produced using arcGIS10 (For interpretation to colours in this figure, the reader is refered to the web version of this article.).