Amphibious People Have Evolved to Sustain Life at Sea
In an exciting discovery for the study of evolution, scientists have found a group of people who have evolved traits that allow them to spend their lives at sea. The Bajau, a people of the Malay Archipelago, live mostly on boats or shallow reefs, and they consume seafood almost exclusively. As a result, they spend as much as 60% of their days underwater, searching for food.
According to The Economist, they are incredible divers. "They sometimes descend more than 70 metres, and can stay submerged for up to five minutes, using nothing more than a set of weights to reduce buoyancy and a pair of wooden goggles...that are resistant to distortion by the pressure at such depth." They and their ancestors have been living like this for up to 1,000 years. Researchers suspected that the Bajau had developed traits over time that would allow them to sustain this life under water. Melissa Ilardo and Rasmus Nielsen of the University of California, Berkeley have found that they were correct.
When one's face is plunged into cold water, there are certain biological responses that are triggered within the body, called "the diving response." The heart rate slows down to conserve oxygen, blood redirects to the heart, lungs and brain, and the spleen contracts, so that extra oxygen-carrying red blood cells are released into the body.
Ilardo and Nielsen were able to get DNA samples from 59 Bajau people, as well as spleen scans. They also got samples from the Saluan, which are a closely related group of people who live on land. What they found is astounding:
[A] mutation in part of the Bajau genome that regulates the activity of a gene known to be involved in controlling blood flow, such that blood can be sent preferentially to oxygen-hungry vital organs. Another was a mutation in a gene responsible for the production of carbonic anhydrase, an enzyme that slows the build up of carbon dioxide in the bloodstream, a phenomenon that is associated with extreme diving. Changes in genes associated with muscle contractions around the spleen and with responses to low oxygen levels also turned up.
The scientists were able to conclude that the Bajau people have evolved to sustain their need to dive for food. They are literally born to dive.