Women living on the Tibetan Plateau have adapted to the oxygen-scarce environment for thousands of years through various evolutionary traits.
A study published in the journal PNAS by Cynthia Beall, a professor at Case Western Reserve University, reveals the adaptive traits that enable Tibetan women not only to survive but also to thrive in the harsh high-altitude environment. Breathing thin air at high altitudes presents a survival challenge, but the research findings indicate that the unique physiological traits of Tibetan women have enhanced their reproductive capabilities despite low oxygen levels in their surroundings, according to Sci Tech Daily.
Tibetan women have developed numerous adaptations to the oxygen-poor environment. (Photo: iStock)
Beall and her team studied 417 Tibetan women aged 46 to 86 living at altitudes of 3,657 – 4,267 meters above sea level in Upper Mustang, Nepal, on the southern edge of the Tibetan Plateau. They collected data on the women’s reproductive history, measured physiological traits, sampled DNA, and assessed social factors. They aimed to understand how oxygen delivery traits facing hypoxemia at high altitudes affect childbirth rates. This is a key measure of successful evolutionary adaptation.
The researchers found that the majority of children exhibited a range of unique blood and heart characteristics that enhance oxygen transport. Women with the highest number of children had hemoglobin (the oxygen-carrying molecule) levels close to the average of the sample but exhibited much higher oxygen saturation, allowing for more efficient oxygen transport to cells without increasing blood viscosity.
“This is a case of ongoing natural selection. Tibetan women are evolving in a way that balances the body’s oxygen needs without overloading the heart,” Beall commented.
Beall’s interdisciplinary research team included Brian Hoit and Kingman Strohl from Case Western Reserve University School of Medicine and several other international scientists, conducting field surveys in 2019. They actively worked with the local community in the Himalayan region of Nepal, hiring local women as research assistants and collaborating with various community leaders.
One genetic trait they studied is likely derived from Denisovan ancestors who lived in Siberia about 50,000 years ago. The descendants of Denisovans later migrated to the Tibetan Plateau. This trait is a variant of the EPAS1 gene, found only in native communities on the Tibetan Plateau, which helps regulate hemoglobin levels. Other traits such as increased blood flow to the lungs and a larger ventricular chamber also enhance oxygen transport. These traits contribute to greater reproductive success, providing insights into how humans adapt to low oxygen levels in their environment throughout their lives.
