Some Questions & Comments Concerning the Bajau Spleen & Freediving

The Sama (called Bajau by the outside world) are prolific freedivers.  People want to know why.  If you ask the Sama about their deepest divers they will tell you the answer is the diver used ilmuꞌIlmuꞌ could be defined as a type of magic or knowledge.  The most renowned spearfishermen and pearl divers are said by other Sama to have learned the ilmuꞌ necessary to stay for great lengths underwater and reach great depths.
Scientists have also asked the question: What makes the Sama great freedivers?  Melissa Ilardo and a team of graduate students from the University of Copenhagen  wanted to find out how Bajau bodies might have adjusted to consume less oxygen or have more oxygen while working underwater.  Contractions in the spleen can increase oxygen in the blood and also the size of the spleen can influence dive time.  They discovered that Bajau spleens in adult males are 50% larger than another genetically related people in Indonesia, the Saluans.  When examining the genetic differences between the groups, several of the areas of genetic variation are thought to produce traits that are possibly favorable for diving.  One of these differences has to do with the thyroid hormone level which might regulate human spleen size in human development and early childhood.  For this group of scientists natural selection is what makes the Sama great freedivers.
When people look for evolutionary reasons that account for why the Sama are so adept in their home environment, immediately a question pops into my mind.

The world’s deepest man Herbert Nitsch pictured with Sama diver Imam Eldio and freediving instructor Wolfgang Dafert.

Why are the Austrians so good?
Ok, I guess a little context for this question might help. My friend Wolfgang Dafert of, who has taken quite an interest in Sama diving technique, is an Austrian.  It is quite true that he is impressed with Sama freediving, but the Sama friends he has made are quite impressed with his freediving too and his spearfishing for that matter.  Even the world’s deepest man, Herbert Nitsch is an Austrian.  The problem is that Austria is landlocked.  It isn’t a great place for the evolutionary changes to occur and enter into Sir Nitsch’s or Wolfgang’s genetics.
The next question that enters into my mind:
What is the mechanism?
We tend to pair evolution with survival of the fittest.  In short, being able to hold their breath underwater for longer has to contribute to a Sama’s ability to stay alive longer and on top of that produce more offspring in order for their genetic variation to become more prevalent in the gene pool.   Most of the economic activities of the Sama are done in relatively shallow water and their former nomadic nature allows them to fish in places where the fish are plentiful.  To this day the homelands of the Sama tend to be shallows, peaceful (climate), and abundant with fish.   Sulu, Tawi-Tawi, Semporna, these are places with tidal flats where you can build a home over the ocean (or place a mooring pole).  There are plenty of coral reefs from 10 to 50 feet.  I’m told that fish aren’t lacking in abundance in these areas even in the modern era where other regions are suffering from over fishing.  Getting a meal for one’s family happens best from 10 to 50 feet.  Not at 200.  If you are a swimmer, 10-50 feet is a lot less intimidating than 200.  A Sama could feed his family and others with a whole variety of livelihoods known to the Sama for centuries without having to go deep or stay in long.
Instead I get the impression that the deeper and longer a Sama can dive, the higher chance he has of dying early or experiencing injuries that could also shorten his lifespan.  The injuries could impact his ability to defend himself against hazards that could later take his life.  In my time living among the Sama, I have met quite a few with lung injuries.  Those who blew their eardrums, did it by accident.  My friend Bapa’ Kinista started diving deeper when his father died and he realized that he needed to provide for his family.  Not knowing what he was doing, he blew his eardrums and was partially deaf.  He lived to an old age, but I would assume deafness would put him at higher risk of dying than those that could hear and be alerted to dangers coming their way.  Several of my Sama diver friends have experienced blackouts while diving.  They only lived because their fishing buddies pulled them out.
Why did the study by the University of Copenhagen pick Saluan people for their control group?
The population of Bajau that Ilardo’s team was interacting with had both divers and non-divers.  The Sama are famous for their diving, but it is only one of many maritime activities that feed their communities.  They trap fish with a variety of traps and nets, fish with hooks for large and small ocean creatures, they fish with other lures, scavenge for edible shellfish at low tide.   I suspect that the “non-divers” in this study still find themselves swimming a lot more than your average Indonesian and that this swimming and interacting with the ocean starts at a young age and has the ability to affect their spleen size.  For instance, my wife is by no means a diver, but as a little kid she remembers chasing sea snakes and diving beneath the hulls of larger boats with her friends.  Only one out of 20 of my wife’s siblings would identify themselves as divers, but they were all chasing sea snakes and swimming underneath large boats in their neighborhoods.
Now I am not familiar with the Saluan people, but in a brief browse through what is available through google search I’m seeing words like remote, farming, mountain.  I suspect that the lifestyle of Saluan children and the lifestyle of Sama children is worlds apart.  What made the researchers believe that Saluan genetics should be close to that of the Sama?  In a follow up study Filipino scientists might consider measuring the spleen size of Yakan.  The Yakan speak a language directly related to the Sama language, but they farm the interior of Basilan.   The West Coast Bajau would also be another viable candidate for a study.  When they arrived on the coast of Sabah, the natives fled inland.  When the Ilanun arrived, the West Coast Bajau moved inland and their culture shifted away from an ocean based people.  Both group’s split from other Sama populations genetically would be so recent it would not allow enough time for the gene pool to shift.  I suspect that they might have smaller spleens than the Sama living over the ocean.
Does this belittle Sama diver’s achievements?
You’ve heard that Bajau children’s eyes have adapted through evolution in a way that allows them to see better than you or I underwater.  This is often repeated, but hasn’t been thoroughly examined scientifically.  Other scientists are hoping to find a connection that demonstrates that humanity used to be aquatic.  Its called the aquatic ape theory.  But why can’t Sama just be good divers because of their upbringing and because of practice and training?
Freediving world record holder Guillaume Néry pictured with me and Sama diver Imam Eldio.

This is where I appreciate the freedivers.  Wolfgang, Guillaume Néry.  They propose neither magic or  thousands of years of adaptation to give a reason for why the Sama are so good.  Instead they assume that the Sama over generations of being connected to the sea have learned techniques and skills that have helped them to dive better.  They have passed these on to their children.  It is now ingrained in their culture, but it still requires hard work, training, and practice.  Several freedivers have come to dive with the Sama, because they think there are things to learn from the Sama about diving.  I suspect there is a lot more to find there than by taking ultrasounds of Bajau spleens.
Here is the study if it still holds your interest:
Physiological and Genetic Adaptations to Diving in Sea Nomads
Otherwise, maybe you would want to read some of the things that the freedivers have discovered about Sama divers:
Learning about Freediving among the Sama

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