How long can you stay underwater? It might depend on the size of your …. wait
for it…spleen. Recent studies have revealed human adaptation to the high altitudes of the Andes and Himalayas. These adaptations involve the ability of blood to carry or hold oxygen in these low-oxygen heights. Now researchers are looking for adaptations in people who spend a lot of time under water. The Bajau people –also known as “Sea Nomads”– have spent thousands of years diving deep underwater without tanks or snorkels. Bajau divers may spend as much as 60 percent of their workday under the surface, spearing fish and harvesting sea cucumbers. mammals, including people have something called a “dive reflex” — which is triggered when you plunge your face into the water. Once submerged, your heart rate slows. Vessels in your extremities constrict- shunting blood to the body’s core. And your spleen gets a big squeeze. This spleen squeeze pumps oxygen-rich red blood cells into the bloodstream. And the researchers in this study found that the Bajau have spleens that are 50 percent larger than their land-based neighbors. It’s possible that these larger spleens may serve as a reservoir for extra oxygenated blood needed for long breathless dives. The researchers then looked to see if there was a genetic component they wanted to know if big spleens are inherited or if something else was going on. After comparing the Bajou DNA with DNA from nearby farmers and from Han Chinese, the team found 25 genes that were different in the Bajou. One notable difference was in a gene called PDE10A. Other researchers had found that in mice, this gene can affect thyroid activity, which in turn affects spleen size. While it is unlikely one gene is responsible for the size of the spleen, the research strongly suggests that there is a genetic component to this spleen enlargement. And it shows whether it’s high-altitude living or deep-diving life, humans have adapted to low-oxygen environments in a number of different ways throughout history I can’t wait to see what we do in space.