The Evidence for Hereditary Factors Contributing to High Altitude Adaptation in Andean Natives: A Review

Abstract

Humans have occupied the high plateaus and mountain valleys of the Andes and the Himalayas for thousands of years. Although sea level natives can, and often do, travel in these rarefied reaches, there is little doubt that natives born and raised in the "thin" air are better equipped to deal with the reduced availability of oxygen at altitude. What fraction of the hypoxia defense response of high altitude native populations is due to developmental adaptations acquired during growth and what fraction is due to a genetic component reflecting the effects of selective transmission of beneficial genetic variants through hundreds of generations of antecedents is as yet unresolved. This paper summarizes some of the studies that have been undertaken to address this issue in Andean indigenous populations, primarily with respect to those adaptations thought to be involved in the uptake, distribution and utilization of oxygen in children and adults. Specifically, it focuses on changes in chest morphology, pulmonary function, metabolism and hematology. Space constraints preclude extending this review to the large body of literature concerning prenatal and maternal adaptations although this critical stage in development has likely been subject to significant selective pressures. It is apparent that both nature and nurture influence the acquisition of a high altitude phenotype in humans and while there is some evidence for genetic adaptation in Andean highlanders, it is evident that these characteristics are expressed in concert with substantial environment-dependent developmental adjustments.