UCL Discovery

Abstract

Human pygmy populations inhabit different regions of the world, from Africa to Melanesia. Their short stature has been interpreted as a consequence of thermoregulatory, nutritional and/or locomotory adaptations to life in tropical forests. A more recent hypothesis proposes that their stature is the outcome of a life history trade-off in high mortality environments, where early reproduction is favoured and, consequently, early sexual maturation and early growth cessation have evolved. Besides some serological evidence of deficiencies in the GH/IGF1 hormone axis have been previously associated with pygmy’s short stature. Using genome-wide SNP genotype data, we first test whether different pygmy groups living in the Philippines and Papua New Guinea are closely related, and secondly investigate genomic signals of recent positive selection in African, Asian and Papuan pygmies. We show that pygmies are genetically more similar to their non-pygmy neighbours than to one another and have experienced positive selection at different genes. These results indicate that geographically distant pygmy groups are likely to have evolved their short stature independently. We also show that selection on common height variants is unlikely to explain their short stature, and that different genes associated with growth, thyroid function and sexual development are under selection in different pygmy groups, suggesting that short stature is likely to be a by-product of other selective processes such as life history trade-offs.