Ipossia ipobarica come fattore selettivo per un complesso di adattamenti bio-culturali nelle popolazioni tibetane

This work attempts to show adaptations of human populations to challenging environments, choosing those of high-altitude Himalayan plateau, in particular the region of Tibet, as a test-case. The potential factor for natural selection is represented by hypobaric hypoxia, where oxygen concentration in air is on average 45% lower than at sea-level, whereas atmospheric pressure halves at 5000m altitude.
This conditions implicate a series of physiological adaptations regarding mainly blood flow:
Firstly, despite what expected, haemoglobin concentration figures at lower levels so as oxygen saturation, especially compared with other populations living at high altitudes, like the Aymara (Bolivian Andes) and the Amhara (Ethiopia highlands).
Second, Tibetans present higher levels of nitric oxide in their lungs. Considering the known advantages which nitric oxide exercises in blood-vessel, one could speculate that this might represent a strong physiological adaptation to hypoxic conditions. Two metabolic ways (one in terms of bioavailability, the other in terms of lesser employ) seem to cooperate in improving the efficiency of oxygen transport.
Third, this work also considers histological differences between high-altitude dwellers and others living at sea-level. We will see that Tibetans have fewer mitochondria in leg-muscle tissue.
Fourth, ventilation taxes, body mass index (BMI) and forced vital capacity (FVR) have proved to reflect adaptations to natural long-term exposure to high-altitude stress.
The aim of anthropological and physiological research in this field, points to examine a possible , or probable genetic background, which attends, integrates and supplants adaption ways which go under the term of “acclimatization”. A genetic evidence underlines the influence of natural selection. So the future bet is to find more genetic factors (besides the already investigated ones) implicated in this mechanism.
Finally, this paper presents a brief overview on the social and cultural implications related to high-altitude adaptations, which involve community organization, family structure and reproductive strategy, like fraternal polyandry. Such biological and cultural adaptations participate in improving the fitness of the whole population, maintaining a successful and ecocompatible lifestyle.
Withal, it is interesting to notice how populations follow different routes to the same functional outcome of successful oxygen delivery. That conclusion will remain tentative, until the responsible genes are identified.
This thesis tries to show the importance of an interdisciplinary approach in studying humans. Anthropology needs necessarily to adopt an interdisciplinary view including genetics, physiology and ecology, working together in the analysis and understanding of human biology.