MESSAGE
| DATE | 2018-04-19 |
| FROM | Ruben Safir
|
| SUBJECT | Subject: [Hangout - NYLXS] I always wondered what the damn spleen was for
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https://www.theguardian.com/science/2018/apr/19/mystery-of-sea-nomads-amazing-ability-to-freedive-is-solved
Mystery of sea nomads' amazing ability to freedive is solved
Scientists have uncovered the secrets of the Bajau people, long-famed
for their ability to hold their breath for extraordinary lengths of time
Nicola Davis
-at-NicolaKSDavis
Thu 19 Apr 2018 12.00 EDT
A Bajau diver holding up a traditional wooden diving mask.
A Bajau diver holding up a traditional wooden diving mask. Photograph:
Melissa Ilardo
The secret behind the ability of a group of “sea nomads” in Southeast
Asia to hold their breath for extraordinary periods of time while
freediving to hunt fish has finally been revealed – and it’s down to
evolution.
The Bajau people are able to dive tens of metres underwater with no
conventional diving aids. Instead they rely on weights, handmade wooden
goggles – and a single breath of air.
But while the Bajau people’s talents have long been known, it was
unclear whether the skill was the result of practice, as in the case of
the excellent underwater vision of Thai “sea nomad” children, or the
result of adaptations which have their roots in the Bajau people’s DNA.
The last of the sea nomads
Read more
Now experts say they have the answer: over time the Bajau people have
undergone natural selection, resulting in certain versions of genes
becoming widespread – many of which are linked to biological changes,
including having a larger spleen, that could help the Bajau to hold
their breath underwater for many minutes at a time.
The team say the findings could eventually prove useful in medical
settings, potentially allowing experts to identify patients that might
be at greater risk of death if they experience a lack of oxygen, for
example during surgery.
“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.
Writing in the journal Cell, the scientists reveal how they unpicked the
mystery following a clue from previous research: species of seals which
can dive for longer have larger than expected spleens – an organ which,
among its functions, can store oxygen-carrying red blood cells.
As a result the team used an ultrasound device to measure the spleen in
43 Bajau people and 33 people from a neighbouring group of farming
people, the Saluan.
“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.
A Bajau diver hunting fish underwater using a traditional spear.
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A Bajau diver hunts fish underwater using a traditional spear
Photograph: Melissa Ilardo
The team note the trend held regardless of whether the Bajau individual
was themselves a diver, and even when factors such as age, sex and
height were taken into account.
Genetic testing revealed that certain versions of 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.
Among them is a form of a gene linked to an increased spleen size – an
effect the team reveal is likely down to an increase in thyroid hormone
levels. Crucially, a contraction of the spleen is one of the features of
the so called “diving reflex” – a set of responses in mammals that occur
when the head is submerged. A large spleen means even more
oxygen-carrying red blood cells can be pumped into the circulatory
system when the organ contracts, allowing individuals to stay underwater
for longer.
A Bajau diver hunting fish on the reef.
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A Bajau diver hunting fish on the reef. Photograph: Melissa Ilardo
Another is a form of a gene linked to a different feature of the diving
reflex: narrowing of the blood vessels to the extremities, aiding
delivery of oxygenated blood to organs such as the brain, heart and lungs.
Further analysis by the team revealed that these 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, saidthe 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.”
--
So many immigrant groups have swept through our town
that Brooklyn, like Atlantis, reaches mythological
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but incompatible with living as a free human being. -RI Safir 2013
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