Magazine article Science & Spirit

Survival of the Highest

Magazine article Science & Spirit

Survival of the Highest

Article excerpt

Researchers from Case Western Reserve University have discovered what might be evolution in action in the Himalayan Mountains. The team found that women with a genetic trait allowing them to carry higher concentrations of oxygen in their blood were more likely to have offspring that live past childhood than were women whose blood carries less oxygen.

Anthropologist Cynthia Beall and her colleagues collected genealogical and fertility data from inhabitants of 900 high-altitude households in Tibet, and tested the inhabitants' hemoglobin, the molecule in the blood that transports oxygen. After controlling for nongenetic factors such as age, illness, and smoking, the team found that a subset of the subjects seemed to have oxygen saturation levels in their hemoglobin that were substantially higher than those of other subjects. The children of these women, the researchers found, were far more likely to survive until the age of fifteen--when they could have offspring of their own.

"Evolutionary theory leads us to hypothesize that if natural selection is acting on a phenotype, it should be associated with higher fertility and higher offspring survival rates," noted Beall, whose findings were reported in the Proceedings of the National Academy of Sciences. How a gene might determine oxygen saturation is uncertain, as is the reason for higher survival rates of the offspring of Tibetan women with higher oxygencarrying capabilities, Beall acknowledged. She suggested that women with higher oxygen saturations might be delivering more oxygen to the uterus, allowing the babies to have healthier immune systems; or the infants themselves may have inherited higher oxygen concentrations, enabling them to better fight off infections. …

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