Among the things the past year has cast in relief is the fact that breathing is not something that simply happens — it is a skillful practice, not to say a political one. Denying a community the right to breathe is a tactic of oppression, as is dismissing its way of breathing as maladaptive. In Tasmania, at the time Europeans first started making their presence felt, breath-hold diving played a key role in foraging strategy. This has been held up as evidence that Tasmanians, under demographic isolation, had entered a devolutionary cycle, foregoing technical innovation in favor of a subsistence strategy that was onerous and unskilled. In this passage, Dr. Josh Berson proposes, to the contrary, that breath-hold diving evinces considerable technical skill, and its transmission demands considerable social scaffolding.
Physiological research on breath-hold diving in northeast Asia dates to 1931, when the Japanese physiologist Gita Teruoka submitted an essay titled “Die Ama und ihre Arbeit” (“The ama and their work”) to the journal Arbeitsphysiologie (Occupational Physiology). From around 1960, the ama and haenyeo (“sea women” in Japanese and Korean) began to attract more sustained attention from physical anthropologists and physiologists. In 1965 the US Office of Naval Research and the US National Academy of Sciences jointly sponsored a symposium on the theme in Tokyo. More recently, the growing popularity of competitive freediving has prompted renewed interest in the physiology of apnea (breath-hold) diving.
The basic ethnographic facts are these. In Japan, ama were found in communities along the Pacific coast from Chiba (east of Tokyo) as far south as Oita in Kyushu, and on the Japan Sea coast from the Oga Peninsula, in Akita, in the north, as far south as Nagasaki prefecture and the islands off the western coast of Kyushu. A cognate tradition of breath-hold diving existed to the south in Okinawa. Most ama dove part-time in the spring, summer, and fall, when the seasonal rhythm of subsistence agriculture allowed, though in some places ama dove in winter too. Some focused their efforts on kelps and other algae, others on gastropods and echinoderms. The details of how they dove varied. In some cases, they swam out to the dive site, tethered themselves to floating casks, and dove unassisted to depths of five to ten meters. In others, they used weights of up to twenty-five kilograms to allow themselves to descend to depths of fifteen to thirty-five meters. The weight was then pulled up by a male partner (a husband, brother, or father) stationed in a boat at the surface. Assisted divers could harvest more than fifty kilograms of algae, mollusks, and echinoderms per day. In Korea, haenyeo were concentrated in Jeju Island, where they dove year-round, swimming out or sometimes taking a boat to sites of five to ten meters’ depth and using gourds for flotation. Census figures are approximate at best. One estimate put the total number of ama in Japan in 1949 at fifteen thousand, declining to seven thousand by 1963. In some parts of Japan men dove too, though their diving and harvest strategies differed from women’s and their numbers were fewer.
In both countries, into the 1970s, divers wore nothing more than a cotton outfit, diving in water as cold as 10 degrees Celsius (the thermal conductance of water is more than twenty times that of air, with a correspondingly greater rate of heat loss from the skin); in some parts of Japan they dove unclothed. In summer, the diving day
comprised three shifts of up to two hours, though at peak harvest times the workday could extend to ten hours; in Jeju, winter shifts could be as short as twenty minutes, with long periods in between warming oneself at a fire on shore. The energy expenditure needed to compensate for heat loss was estimated at one thousand kilocalories for a day of diving, made up for by a greater food intake, relative to nondiving peers, in the morning and evening. By 1930, ama in Japan had begun adopting face masks. Prior to this they dove without masks, identifying edibles without benefit of corneal vision. In both traditions, dives were short—in unassisted methods, prior to the introduction of wetsuits, on the order of a minute, with half that time submerged and half resting at the surface. Girls would start diving at eleven or twelve, first in about a meter of water, attaining status as fully competent divers at seventeen or eighteen. Some continued working into their seventies.
Physiologically, cold-water apnea diving represents one of the most extreme instances of somatic plasticity in the history of humanity. As you would expect, breath-hold divers exhibit enhanced vital capacity—the volume of air they can take in with a breath—and enhanced mobility in the thoracic cage. But these pale in comparison to the thermoregulatory conditioning they exhibit. Haenyeo working prior to the introduction of wetsuits in the late 1970s were found to have peripheral tissue insulative capacities superior to those recorded among Inuit. This was not due to subcutaneous fat deposits—in fact, haenyeo tended to be leaner than nondiving controls. Rather, they seem to have exhibited a combination of vasoconstrictive adaptation and enhanced brown adipose tissue thermogenesis of the type discussed in the last chapter.
More broadly, apnea diving presents formidable challenges both physiological and biomechanical. These include pressure: every ten meters of submersion below sea level introduces an additional quantity of pressure comparable to atmospheric pressure, so at twenty meters you experience three times the pressure on the thoracic wall
and tympana (eardrums) that you would at the surface. Barotraumas of descent include pulmonary edema, alveolar bleeding, and atalectasis (lung collapse). These have been observed in single-bout dives as shallow as thirty meters, and evidence of pulmonary edema from prolonged surface swimming suggests that the repeated-dive pattern typical of ama and haenyeo would incur a heightened risk of edema even at relatively shallow depths. Ascent carries its own dangers, as the rapid depressurization of the lungs reduces the partial pressure of oxygen, creating a risk of hypoxia and loss of consciousness. Hypoxia of ascent is compounded by alternobaric vertigo, in which asymmetric changes in pressure in the middle ear between the two sides of the head can cause loss of awareness of one’s rotational orientation.
Diving fasted, as was and is typical of haenyeo and ama, increases risk, as lipid metabolism is both less efficient than carbohydrate metabolism and generates less CO2—you experience hypoxia faster, and your main chemoreceptive cue to breathe, carbon dioxide accumulation in the blood vessels and lungs, is depressed. Head submersion induces a combination of transient hypertension and bradycardia (slowed heart rhythm), combined, in cold water, with constriction of the airways—a pattern that ama and haenyeo experience up to 150 times a day. The risks of habitual diving, even to depths of no more than five or ten meters, include hypernitrogenemia (toxic nitrogen partial pressure) of the lungs, hearing loss, and tinnitus.
In Jeju, diving was regarded as a marginal occupation. In 1960, 40 percent of haenyeo were their family’s primary earner. More than three-fifths said they would prefer to make their living some other way, and 64 percent said they would not allow their daughters to become haenyeo. Whether circumstances had been equally desperate in earlier eras is impossible to say. In 1960, Korea was still recovering from thirty-five years (1910–1945) of Japanese colonial rule and twenty-two years (1931–1953) of nearly continuous war. Still, looking at the Jeju case, we can identify an intuition, reasonable if shallow, underlying Henrich’s dismissal of breath-hold diving in Tasmania: given the choice, most people would prefer to get their living in a less laborious, less risky way.
The question then becomes: What is laborious and what is risky? Labillardière and his contemporaries were impressed with the effort that Tasmanians, particularly the women, put into the work of securing food, but their accounts do not suggest Tasmanians were malnourished, nor that they found the food-gathering task oppressive. Comparative energy expenditure provides one rubric for ranking ways of life as more or less effortful, but energy expenditure is inadequate on its own. It tells us little about perceived effort, not to say satisfaction both in the exercise of skill (say, identifying and harvesting a range of targets sessile and motile without corneal vision under the biomechanical, thermal, and respiratory constraints of diving) and in coordinate effort.
These are the kinds of factors—perceived effort, satisfaction— that skill transmission modelers would dismiss as fluffy-headed conjecture with no material influence on the choices people make about how to keep themselves fed and sheltered. But this dismissal is unwarranted. What makes, say, satisfaction suspect is not that we have no evidence it plays a part in shaping how people act but that it is more difficult to operationalize—to assign scalar or even ordinal (rank) values to—than, say, energy expenditure or the number of parts in a tool.
I would go so far as to say that the difference between survival and flourishing is that the latter incorporates measures of perceived effort and satisfaction. Here we can start to see what is lacking in the theory of adaptation at work in skill transmission models. A theory of adaptation in the Darwinian sense—how circumstance shapes behavior to maximize reproductive fitness—will do a poor job characterizing change in human behavior over time. There are at least three reasons for this. One is that adaptation, as we’ve seen, is not simply a reaction to extrinsic change—it is a process of niche construction in which the community has a hand in shaping its environmental scaffold. A second reason why adaptation is conceptually brittle is that human life history is exceptional, among animals, for its elongated character, both during development and following reproductive senescence. Many of the selective cues that shape the human niche are most active in the postreproductive phase of life. The third reason to look beyond adaptation is that many of the cues that shape our behavior operate in the domain of flourishing rather than survival—the exceptional pleasure we take in participating in coordinate activity, for instance, or in the exercise of motor skill. Often these do contribute directly to a community’s reproductive success, as in collaborative foraging and childrearing, but just as often they stand orthogonal to or in tension with reproduction.
Whether to track survival or flourishing is a value-laden decision. So is whether to treat change over time in culturally salient behavior as a process of adaptation or niche construction. These decisions overlap with, but are not identical to, decisions about what kinds of scaffolds we should expect to find when we examine adaptive behavior: technological? or enactive? Enactive is a new term, but it describes something we’ve observed repeatedly in this chapter and the last: situations in which the material residues of action are ephemeral but the action recurs and coalesces into enregistered patterns by virtue of how it becomes coupled to sensorimotor tendency. Critically, this coupling is dyadic: practice is a big part of how we transform a cascade of actions into embodied skill, but for something to really stick in the community, it needs to get passed back and forth between individuals—and your own performance, in the moment and over time, must become contingent on what you’ve learned to expect others to do.