Dienekes reports on this in-press AJHG paper, by Matthew A. Saunders, Jeffrey M. Good, Elizabeth C. Lawrence, Robert E. Ferrell, Wen-Hsiung Li and Michael W. Nachman, entitled Human adaptive evolution at Myostatin, a regulator of muscle growth
The authors find strong evidence of (maybe diversifying) selection in humans on some variants of the Myostatin gene (GDF8), which encodes a negative regulator of skeletal muscle growth. They also find somewhat large differences in frequency of these mutations between sub-Saharan Africans (up to 31%) and rare in others.
The authors don't mention much about the implications of this in terms of adaptation, except for a passing mention that "one of the many possible adaptive implications of such an effect could be protection from muscle-wasting in times of famine, a potentially recurrent phenomenon for early agricultural societies."
This gene falls in a line of other muscle related genes found to have population differences, the main one being ACTN3.