The secret behind the extraordinary ability to hold breathe for a long period while freediving to hunt fish by a group of “Sea nomads” or the Bajau in Southeast Asia remained unclear, whether the skill was the result of practic or the result of adaptations which have their roots in the Bajau people’s DNA.. Scientists have finally unlocked the secret which credits evolutionary adaptation.
For normal human being, it is very difficult to breathe underwater for few seconds or for few minutes. But this ethnic group of Bajau people can free dive underwater as long as 13 minutes at depths of 200 feet without any conventional diving aids. These nomadic people have been living for hundreds of years at sea winding through the Philippines, Malaysia, and Indonesia, where they dive to hunt for fish or search for natural elements that can be used in crafts.
“There seems to be so much to learn from the Bajau and other diving populations about how the human body is able to react to oxygen deprivation, which is an important medical issue,” said Dr Melissa Ilardo, first author of the study who was at the University of Copenhagen at the time of the research.
The first clue was derived from a study in the journal Cell which hinted that a DNA mutation for larger spleens gives the Bajau a genetic advantage for life in the deep. However, it is quite interesting to know that human beings can technically live without it, but while you have it, the organ helps support your immune system and recycle red blood cells.
In a study 43 Bajau people and 33 people from a neighbouring group of farming people, the Saluan were examined with a ultrasound device to measure spleen size.
“The spleen size is about 50% larger in these sea nomads than it is in the [Saluan], so already it was like ‘Oh my God – it is really [an] extreme physiological characteristic,” said Prof Eske Willerslev, a co-author of the study from the University of Cambridge.
Further in a genetic testing it was revealed that genes are more commonly found in Bajau people than would be expected, with many apparently linked to biological changes that could help individuals cope with low-oxygen conditions.
The team also revealed a gene linked to a increased spleen size result in increase in thyroid hormone levels. Diving reflex is a set of response found in mammals due to contractions of spleen when head in submerged in water. A large spleen helps in oxygen-carrying red blood cells can be pumped into the circulatory system when the organ contracts, allowing individuals to stay underwater for longer.
Further the study reveals that genetic boons are not the result of chance, but evolutionary adaptations arising from natural selection.
Stephen Stearns, professor of ecology and evolutionary biology at Yale University who was not involved in the research, said the study adds to evidence for recent natural selection on certain genes in human populations – with previous examples including genes for lactose tolerance that cropped up with the advent of domestication of dairy animals, and genes for adaptation to high altitude in Tibetans and Native Americans in the Andes.
“What we lack at this point, and badly need, are samples large enough to allow us to infer when the selection [in the Bajau] started to happen,” he said. “We know that the Bajau have been leading this lifestyle for at least a thousand years, but we do not know when they started it – perhaps much earlier.”
However, the sea nomad lifestyle is increasingly under threat. They’re considered marginalized groups that don’t enjoy the same citizenship rights as their mainland counterparts. Increased industrial fishing is also making it harder for them to subsist on local stocks. As a result, many choose to leave the sea.
Without support for their way of life, Llardo worries that the Bajau and the lessons they can impart about human health may not be around for much longer.