Classically, the short stature of human pygmies was thought to confer a selective advantage for forest life or to provide greater resistance to starvation, but not all pygmy groups are forest dwellers or short of food. In an investigation of the Aeta, a Philippine pygmy group with a life expectancy at birth of only 16.5 years, Migliano et al. discovered that young women stop growing between the ages of 12 and 13, and that their reproductive fitness peaks at 15 years of age when they have attained an average height of 140 cm. By comparison to a similarly nourished group, the Turkana women of East Africa start reproducing at an average age of 22 years. At birth, Turkana women can expect to survive 48 years, and by 18 to 19 years have reached an average adult height of 166 cm. Although larger adult size results in fertility gains and greater child survival, for a pygmy anywhere in the world, it appears to be too risky to wait; instead, it seems to pay to grow up fast and have babies before disaster hits. Whether this is a consequence of unusual burdens of infectious disease or vulnerability to other, as yet unknown, hardships, it remains unclear why pygmies have such low life expectancies. -- CA
Proc. Natl. Acad. Sci. U.S.A. 104, 20216 (2007).
