Human (amphibious model): living in and on the water

by Daniel Lende in Neuroanthropology PLoS

At the beginning of the film clip, Bajau fisherman Sulbin sits on the side of a boat on the coast of Borneo, gulping air, handling his speargun.  And then, he drops into the water.  The footage suddenly changes and becomes arresting: silent, dreamy, slow, and so blue.  Sulbin strokes deliberately and descends until he strides along the bottom of the ocean, holding his breath, and hunts for fish through handmade goggles.
Finally, after a couple of minutes, he spears a fish and heads for the surface.  The narrator tells us that Sulbin could stay down twice as long and dive deeper if necessary.  Most viewers, unfamiliar with free diving, exceptional if they can hold their breath longer than thirty seconds, are quite likely to be shaking their heads by the end of the clip, wondering at the ability of the human body to adapt to life in water.  Life as an amphibious human can appear so alien that it’s stranger than science fiction, but painfully beautiful to watch.

I stumbled across the video clip in part because of my academic interest in free diving. Earlier this month, I was supposed to attend a free diving workshop in New Zealand with one of the sport’s world record holder, Will Trubridge (or see the story on the Times Online).  The workshop fell through at almost the same time I was diagnosed with multiple hernias, so my first free diving experience likely wouldn’t have worked out – I’m still hoping to do it as part of my ethnographic research on extraordinary human performance in the near future.
But the clip of Sulbin on the BBC series, Human Planet episode, Oceans, has inspired me to write a little bit about Homo aquaticus (kidding), adaptation, culture, and what this sort of remarkable human adaptation might imply for the idea of ‘human nature.’
Sulbin’s ability is remarkable, but like so many exceptional human skills, it relies not on innate difference from other individuals, but on the steady cultivation of peculiar changes in the body and in how it is experienced.  What I hope to suggest is that amphibious humans point to the most basic fact of human nature: that we seem particularly adept at finding ways to adapt ourselves – biologically, psychologically, behaviourally, technologically – to a host of niches that then rebound back upon us and shape how we develop.  We are a peculiar self-made species.

This piece is probably best seen as one in a series I’ve been crafting on how human adaptation to situations that we place ourselves in map out the envelope of our bodies’ malleability.  Human skills and adaptation show us how our brains and nervous systems can be trained to do amazing things.  Frequent readers will know that I think much of the discussion of ‘human nature,’ carried out by — to put it nicely — exceptionally sedentary theorists, severely underestimates what our bodies are capable of doing.
Too often, in discussions of human adaptation, we allow a flabby distinction between three basic types of adaptation: genetic, phenotypic (or physiological), and cultural (or technology).  What I’ve been playing with, and will return to at the end of this piece, is the inseparability of these, especially the last two: physiology and culture.  The Bajau fisherman Sulbin shows us how biology and culture are inseparable because what he does ends up shaping his body, but only because he grew up around people who knew how to manage becoming human in this distinctive amphibious way and because his adaptations play upon how his nervous system works, including some intriguing quirks.
If you’re mad keen to learn more about human adaptation and my ongoing obsession, you might check out samples of my work on human quadrupedalism (part two), barefoot running, barefoot climbing, and even overhand throwing (the piece is specifically on ‘throwing like a girl’).  I’ll be posting more in the months to come, so if you’re interested in what the human body can be made to do, pay us a return visit periodically.
‘Sea gypsies’ in Southeast Asia
Sulbin is a member of a number of groups who live wholly or partially as oceanic nomads or sea foragers in South-East Asia.  As the BBC website explains:
Few peoples have a deeper connection with the sea than the Bajau Laut of South-East Asia. Sometimes known as “sea gypsies”, they live in house boats or stilt houses built on top of coral reefs and when they do spend the occasional night on solid ground they often report feeling ‘landsick’.
Malaysia’s best Bajau free-divers can dive to depths of over 20 metres and stay there for several minutes on a single breath as they go in search of fish. And as if that weren’t enough, studies on some “sea gypsy” children from Thailand and Burma show that they have unusually good underwater-vision because their eyes have adapted to the liquid environment.
The Bajau Laut’s livelihood is traditionally totally dependent on the resources of the sea so spear-fishing is vitally important to them, but different cultures have very different ways of catching fish.  (BBC website).
I won’t go into the ethnographic material on the Bajau and other groups called ‘sea gypsies’ (such as the Moken, who live along the coasts of Thailand, Burma and increasingly into Malaysia).  If you’re interested, I’ve placed some links to more material on the Moken and other groups at the end of this article.  Some of the groups experienced a recent spike in interest when they apparently avoided serious casualties in the Boxing Day Tsunami of 2004 because they ‘saw signs in the waves’ of the trouble to come.
This post is really about adapting to diving, and that happens a lot more broadly than just in ‘sea gypsy’ populations.  Although SCUBA and other techniques are replacing breath-hold diving, traditional divers cultivated incredible abilities in the production of sponges in Greece, and pearls in places like Polynesia and the Persian Gulf.  The practice is still widespread among recreational divers, competitive divers, and even in some industries, such as among seafood harvesters in Japan and Korea, where an estimated 20,000 professional divers still worked with minimal equipment as late as the 1990s (see Park et al. 1990, cited in Ferretti 2001).
Learning to ‘hold’ your breath
Freediving: Ewens Ponds
Human ‘adaptation’ to water is both conscious and unconscious, as so many things about human behaviour.  Even the most basic adaptive reflexes have to be shaped and elaborated, although they can often be learned in implicit, indirect ways or found in basic form very early.  For example, one of the most reliable reactions to a startling new sensation is to gasp, a potentially deadly maladaptive approach to dealing with being dunked in the water.  Fortunately, when water hits the pharynx or larynx, glottal spasms clamp the throat shut with a glottal spasm in part of what is referred to as the ‘diving reflex’.
If we’re going to enjoy the whole underwater swimming experience, however, we’ve got to be taught to stop the airway voluntarily and close the glottis muscularly, or to exhale. It’s more pleasant than just plunging into the water and trusting that the ‘diving reflex’ will save you from winding up with a couple of lungs full of the stuff by triggering a glottal spasm.  In other words, the reflex has to be cultivated into a skill.
The online web resource eHow suggests, in How to Teach a Baby to Hold Breath Underwater, that you first condition an infant by essentially an associative learning process where dipping a washcloth in water is followed shortly by dripping water over his or her face.  The writer advocates following this up at a pool with a learned association between ‘1… 2… 3…’ and subsequently being splashed in the face, later substituted by short immersion.  The diving reflex can cue the early learning, but the goal is to build a more robust v... Read more »