Up high in the Himalayas, where wind rips through the world's tallest peaks, the air is thin and the cold is bone-chilling. Surviving in this extreme environment is challenging. But strangely, this environment is linked to an unexpected, lasting upside for the populations who call it home.
The Mosuo people, a Tibetan-descended population currently living in the mountains of Southwest China, have thrived in high-altitude for thousands of years. New research shows that their long history in the Himalayas has resulted in distinct health advantages, buried in their genes, that linger today.
After analyzing the health metrics of this group, researchers noticed an odd phenomenon: They appeared to be partially protected from lifestyle changes that would typically spike the risk of chronic disease. The Mosuo have a lower risk of diabetes-associated anemia and high blood pressure than populations without high-altitude ancestors, the study shows.
This study was published Wednesday in the journal American Journal of Physical Anthropology.
The discovery of this unique high-altitude genetic adaptation underscores how the environment can shape future survival.
“Genes and environment together determine health,” co-authors Siobhan Mattison, an anthropologist at the University of New Mexico, and Tami Blumenfield, an anthropologist at Yunnan University, tell Inverse.
“So much research has focused on one or the other, but the interaction is really critical.”
Why past adaptations affect present health — Today, the Mosuo people live about 2,638 meters above sea level. In comparison, New York City is about 33 meters above sea level. But the ancestors of the Mosuo lived at an even higher altitude: 5,400 meters.
These findings suggest that staying healthy and staving off disease depends on a constellation of factors, including environmental factors from centuries past. The researchers say the study illuminates a new way of looking at public health, and preventative measures.
As the "tremendously increasing burden of chronic disease" reaches different communities, we can't assume that one-size-fits-all in terms of public health intervention, co-author Katherine Wander, an anthropologist at Binghamton University, tells Inverse.
In the last decade, tourism around the Lugu Lake area of Yunnan where the Mosuo community currently lives has boomed, providing new employment opportunities and market integration. Rather than herding or cultivating crops, many people are participating in wage labor, Wander says. In turn, traditional daily diet and activity patterns of the group are changing rapidly.
“Changes to the local diet in the last decade have been significant," the researchers report. Prior to tourism's surge around Lugu Lake, the community primarily grew all their own food and ate seasonal vegetables. Meat was hard to come by unless an egg-laying chicken was sacrificed.
Today, people generally eat more purchased foods, including more processed foods, sugary beverages, meat, and non-local fruits and vegetables, the researchers say. Snacking is on the rise and prepackaged cookies and savory snacks are popular. Meanwhile, there's less time engaging in agriculture and fewer opportunities to be physically active.
The researchers aimed to see how these lifestyle shifts manifested in health outcomes. Typically, when communities make these transitions, their risk of chronic disease escalates, Wander says.
Between 2017 and 2018, the team went door to door interviewing hundreds of Mosuo families. They asked people about their livelihoods, measured blood pressure, and took finger-prick blood samples to capture their inflammation, diabetes, iron deficiency, and anemia levels.
They honed in on two chronic diseases: hypertension (or high blood pressure) and diabetes-associated anemia. This type of anemia is a deficiency of red blood cells or of hemoglobin in the blood, which can make you feel tired or weak, and is fairly common in people with diabetes.
They compared these findings gathered on the ground to data from the Chinese National Health Survey. Specifically, they analyzed health metrics from the Han community living in the Hunan province.
Both the Mosuo and Han groups currently live at altitudes of about 2,638 meters and share similar risk factors (diet and activity levels) for chronic disease. The major difference? The Mosuo's ancestors lived on the Tibetan Plateau, about 5,400 meters above sea level, for an estimated 1,500 years.
This one factor is linked to some crucial outcomes: The researchers found that although hypertension was common in both groups, it was significantly lower in the Mosuo. In contrast, diabetes was common in both groups but more prevalent in the Mosuo. However: Diabetes was associated with anemia in the Han, but not the Mosuo.
The researchers hypothesize that the Mosuo’s protection to hypertension and diabetes-associated anemia stems from the genetic adaptations seen in other descendants of Tibetan Plateau natives. These adaptations increase blood flow and enhance oxygen delivery to tissues without dramatic increases in red blood cell production, and seem to protect against chronic disease.
The high-altitude genetic adaptations of the Mosuo people are a clear example of genes and the environment working together to shape health outcomes, the researchers assert. But they say this interaction extends beyond the Himalayas, to any population with “long-term genetic adaptations to a particular local environment.”
"Obesity and other chronic diseases are an increasingly global phenomenon, and so it is important to understand how differences across populations interact with the physiology of chronic diseases — high-altitude adaptations are just one example of such an interaction," Wander says
This doesn’t mean ten years living in Denver will protect you against chronic disease, but it could mean that the habits and location of your ancient relatives influence your health in meaningful ways.
Background: Human populations native to high altitude exhibit numerous genetic adaptations to hypobaric hypoxia. Among Tibetan Plateau peoples, these include increased vasodilation and uncoupling of erythropoiesis from hypoxia.
Objective/Methods: We tested the hypothesis that these high-altitude adaptations reduce risk for hypertension and diabetes-associated anemia among the Mosuo, a Tibetan-descended population in the mountains of Southwest China that is experiencing rapid economic change and increased chronic disease risk.
Results: Hypertension was substantially less common among Mosuo than low-altitude Han populations, and models fit to the Han predicted higher probability of hypertension than models fit to the Mosuo. Diabetes was positively associated with anemia among the Han, but not the Mosuo.
Conclusion: The Mosuo have lower risk for hypertension and diabetes-associated anemia than the Han, supporting the hypothesis that high-altitude adaptations affecting blood and circulation intersect with chronic disease processes to lower risk for these outcomes. As chronic diseases continue to grow as global health concerns, it is important to investigate how they may be affected by local genetic adaptations.