OUR ANCESTRAL PHYSIOLOGICAL PHENOTYPE - AN ADAPTATION FOR HYPOXIA TOLERANCE AND FOR ENDURANCE PERFORMANCE

There are well known mechanistic similarities in human physiology betw een adaptations for endurance performance and hypoxia tolerance, By us ing background principles arising from recent studies of the evolution of the diving response in marine mammals, here we analyze human respo nses to hypobaric hypoxia based on studies with several different low and high altitude human lineages. As in the evolution of the diving re sponse in pinnipeds, we found ''conservative'' and ''adaptable'' physi ological characters involved in human responses to hypoxia. Because th e analysis concerns traits within a single species, conservative chara cters dominate the picture (they define basic human physiology and lar gely are independent of environmental parameters). Most notably, we al so found evidence for adaptable characters forming the foundations for a fairly unique physiologic al phenotype-a low capacity version favor ed under hypobaric hypoxia and a high capacity one favored for enduran ce performance, Because current evidence implies that the human specie s arose under conditions that were getting colder, drier, and higher ( situations in which these traits would have been advantageous), we hyp othesize that this physiology is our ''ancestral'' condition.