Tibetan Women Demonstrate Ongoing Human Evolution, Adapting too High-Altitude Life
Kathmandu, Nepal – October 26, 2024 – A new study published in the Proceedings of the National Academy of Sciences reveals compelling evidence of ongoing human evolution in Tibetan women, demonstrating physiological adaptations that allow them to thrive at extreme altitudes with remarkable reproductive success. Researchers have identified a unique combination of traits that maximize oxygen delivery without placing undue strain on the heart, offering a window into the processes of natural selection in real-time.
For generations, scientists have observed that Tibetans living at high altitudes exhibit lower hemoglobin concentrations than most populations. This study, led by Dr. Cynthia Beall of case Western Reserve University, builds on that knowledge, revealing a more nuanced picture. The research team found that an intermediate level of hemoglobin, coupled with high oxygen saturation, provides the greatest benefit.
“Previously we knew that lower hemoglobin was beneficial, now we understand that an intermediate value has the highest benefit. We knew that higher oxygen saturation of hemoglobin was beneficial,now we understand that the higher the saturation the more beneficial. The number of live births quantifies the benefits,” Beall stated.
The study focused on oxygen transport traits and reproductive success in Nepalese women. Researchers discovered that women with the highest rates of live births also exhibited high blood flow to the lungs and larger-than-average left ventricles – the heart chamber responsible for pumping oxygenated blood throughout the body. These combined traits effectively increase the rate of oxygen transport and delivery, compensating for the thinner air at high altitudes.
Interestingly, the research showed that women coudl maintain high reproductive rates even with lower values in some oxygen transport traits, provided they possessed favorable values in others. “It was unexpected to find that women can have many live births with low values of some oxygen transport traits if they have favorable values of other oxygen transport traits,” beall explained.
While cultural factors like early age of frist reproduction and longer marriages were also found to contribute to higher birth rates, the study emphasizes the meaningful role of these physical adaptations. Women with physiologies most similar to those in low-altitude environments demonstrated the highest reproductive success.
“This is a case of ongoing natural selection,” Beall concluded.”Understanding how populations like these adapt gives us a better grasp of the processes of human evolution.”
This research provides a powerful example of how humans continue to evolve in response to environmental pressures, offering valuable insights into the mechanisms driving adaptation and the resilience of the human species.
Link to original ScienceAlert article
Link to PNAS publication
