Summary
At high altitude human face a unique stress of hypobaric hypoxia due to reduced fall in barometric pressure and the extent of oxygen molecules, therefore, studying humans at high altitude facilitates the understanding of adaptation capabilities of human against evolution as well as environment.
The following essay summarizes an article authored by Beall that studied the arterial-oxygen-content phenotypes of three high-altitude inhabitant populations residing on Tibetan, Andean, and Ethiopian plateaus. The article is based on the problem that how people possess diverse adaptation potential on different heights where the oxygen level is very low in comparison of normal sea level. The author cited previous hypotheses stating that the essential evolution to survive this pressure had occurred in human ancestral phenotypes under the conditions of minor hypoxia (Beall 18-24).
This literature review evaluated the target populations on three primary principles that were the percentage of O2 Saturation (O2 sat.%), the hemoglobin concentration (gm/dL) and arterial O2 content (mLO2/100mL blood). The article illustrated the remarkable facts regarding the phenotypes of targeting populace. It demonstrated that Tibetan and Andean highlanders have a different phenotype which shows elevated hemoglobin concentration though Andeans possess comparatively high hemoglobin concentration. Moreover, no heritability pattern was found for oxygen saturation in hemoglobin among Andean people, but Tibetans exhibited an autosomal dominant gene responsible for greater oxygen saturation. While values of both traits, hemoglobin concentration and oxygen saturation in hemoglobin were observed similar between Ethiopian highlanders and sea-level inhabitants. The article also highlighted that the females with high oxygen saturation genotypes delivered more surviving offsprings (Beall 21).
Article supported the hypothesis claiming the significant favoring role of natural selection towards the higher oxygen saturation allele. The article concluded that the settlement of high altitude uplands on three different continents has led to the three quantitatively different arterial oxygen-content phenotypes among the target populations. Overall, the article presented valuable insights regarding the phenotype and genotype of Tibetan, Andean, and Ethiopian populations that have been evolved during the constant process of natural selection.
Works Cited
Beall, C. M. "Andean, Tibetan, And Ethiopian Patterns Of Adaptation To High-Altitude Hypoxia".
Integrative And Comparative Biology, vol 46, no. 1, 2006, pp. 18-24. Oxford University
Press (OUP), doi:10.1093/icb/icj004.
