PETALING JAYA: The Bajau people of South-East Asia, known for their diving skills, have evolved over time to literally become a people born to dive, according to a scientific report.
A study published in the journal Cell said the Bajau had a spleen that was 50% larger than the related Saluan people.
“This suggests that it is Bajau lineage, rather than the actual activity of diving, which is responsible for a larger spleen,” the study said.
The spleen acts as a biological “scuba tank” during long dives, and a larger spleen makes more oxygen available in their blood for diving.
The Bajau are known for an extraordinary ability to hold their breath.
Melissa Ilardo, of the University of Copenhagen, the first author of the study, told the BBC: “It’s not clear how long the Bajau have had this lifestyle, or when exactly the adaptation arose given the genetic data that we have now.”
However, the data showed that the Bajau diverged from the non-diving Saluan around 15,000 years ago.
According to the Economist, DNA analysis also showed a mutation of a gene allowing oxygen to be preferentially sent to oxygen-hungry vital organs.
Another mutation was found to slow down carbon dioxide build-up in the blood stream, a phenomenon associated with extreme diving, and changes in genes associated with muscle contractions around the spleen and responses to low oxygen levels.
The Bajau people live across the southern Philippines, Indonesia and Malaysia and, according to rough estimates, number about one million people.
They have been traditionally nomadic and seafaring, and survive by collecting shellfish from the sea floor.
Dr Ilardo said: “When they’re diving in the traditional way, they dive repeatedly for about eight hours a day, spending about 60% of their time underwater. So this could be anything from 30 seconds to several minutes, but they’re diving to depths of over 70m.”
These dives are performed only with a wooden mask or goggles and a weight belt, it said
Dr Ilardo took a portable ultrasound machine to an area of Indonesia where the Bajau live to stuy their spleens. The research team also comparied the genomes (the total complement of DNA in the nuclei of human cells) of the Bajau, the Saluan and Han Chinese.