This Organ Helps Sea Nomads Dive Deeper for Longer

A Bajau diver hunting fish underwater. (Credit: Melissa Ilardo) When we think of the organs that help humans stay alive under the water, the heart and lungs top the list. But there's another organ that deserves recognition as well, though few of us would think to name it. It's the spleen. Mammals have a unique response to having our faces engulfed by water. Our heart rate slows and peripheral blood vessels constrict, shunting blood to vital organs where it's needed most. At the same time, our spleens release a cache of red blood vessels held for this express purpose, giving our blood an increased ability to transport oxygen to vital organs. It's a mechanism that gives us a boost under the water, and for a group of free-diving fisherman in Indonesia, it might be what allows them to spend up to eight hours a day diving for fish in the Pacific Ocean. A recent study of the Bajau people, also called the Sea Nomads, shows that their spleens are much larger than normal, and researchers from the University of Copenhagen think it's the result of genetic adaptions to centuries of spearfishing and shellfish-gathering.