Evolution of the human pygmy phenotype

Small human body size, or the 'pygmy' phenotype, is characteristic of certain African, Southeast Asian and South American populations. The convergent evolution of this phenotype, and its strong association with tropical rainforests, have motivated adaptive hypotheses that stress the advantages of small size for coping with food limitation, warm, humid conditions and dense forest undergrowth. Most recently, a life-history model has been used to suggest that the human pygmy phenotype is a consequence of early growth cessation that evolved to facilitate early reproductive onset amid conditions of high adult mortality. As we discuss here, these adaptive scenarios are not mutually exclusive and should be evaluated in consort. Findings from this area of research are expected to inform interpretations of diversity in the hominin fossil record, including the purported small-bodied species Homo floresiensis.