A pre-print in AJHG discusses Myostatin, a negative regulator of muscle growth. Loss of function mutations in Myostatin cause organisms to grow bigger muscles. According to this study, two variants of this gene have been under recent positive selection, reaching relatively high frequencies in sub-Saharan Africans but being rare elsewhere.
American Journal of Human Genetics (preprint)
Human adaptive evolution at Myostatin, a regulator of muscle growth
Matthew A. Saunders et al.
Myostatin (GDF8) is a negative regulator of muscle growth in mammals and loss of-function mutations are associated with increased skeletal muscle mass in mice, cattle and humans. Here we show that positive natural selection has acted on human nucleotide variation at GDF8 as the observed ratio of non-synonymous to synonymous changes among humans is significantly greater than expected under the neutral model and is strikingly different from patterns observed across mammalian orders. Furthermore, extended haplotypes around GDF8 suggest that two amino acid variants have been subject to recent positive selection. Both mutations are rare among non-Africans yet are at frequencies of up to 31% in sub-Saharan Africans. These signatures of selection at the molecular level suggest that human variation at GDF8 is associated with functional
Link (preprint pdf)