Once upon a time there was a blue planet that was inhabited by many forms of life, all of which dwelled in the vast expanses and dark depths of its oceans. In the distant past, over many thousands of years some of these forms of life evolved into land dwellers. After much catastrophe, inconceivable periods of time and a myriad of evolutionary changes, some forms of life re-entered the sea. Dolphins and whales are the better known of these. They moved in water but breathed air at the waters surface. Though it might be supposed that this would hinder greatly their aquatic ability, it is known today that some of these creatures can dive to depths below 3000 metres.
According to the laws of physics this extreme pressure should prove fatal to an air breathing animal, crushing the lungs to 1/100 of their natural size. And so it would be, except that mother nature is ingenious at adapting the laws of physics to her advantage. And so it is that these wonderful animals can resist these incredible changes of pressure.
In the case of deep dives when the pressure reduces the lungs below their residual volume, instead of imploding the body of the whale, this vacuum sucks blood in from the extremities of the body. This’ blood shift’ concentrates oxygen around the vital organs. With this shift there is also a compression of some organs which releases more oxygen rich blood. Another very important change that happens is that the heart and metabolism slow down (bradycardia) thus reducing the bodies need for oxygen.
These remarkable adaptations mean that a whale can take a breath of air at the surface and dive to incredible depths for many minutes without endangering itself in any way. This reflex is called the Mammalian Dive Reflex (MDR)
At some point in our evolutionary development Mother Nature gave us a similar ability to dive to depth, though to a lesser degree. Mother Nature is not given to random generosity, so it seems likely that at one point in our history an ability to forage in the ocean gave us that needed evolutionary edge in the race for survival. Over thousands of years, an ability to dive to depth has lost its evolutionary importance, though still we’ve kept the reflex, albeit in a dormant form.
In the mid twentieth century when free-divers neared the fifty metre mark one doctor famously predicted that anyone diving below that point would be fatally crushed by the pressure. In 1962 the myth was resolutely disproved by Enzo Maiorcas, who went on to dominate the new sport of deep free-diving for two decades.
Today free-divers have reached depths below 200 metres without injury. This is all due to the mammalian dive reflex. Though we don’t possess it to the same degree as our aquatic cousins we still have it. It may be somewhat dormant, but with the insight of science and the efforts of the world’s top apneists it is clear that the MDR is like anything in nature, practice makes perfect. Some of the worlds top apneists have been seen to trigger a visible blood shift by just holding their breath while at the surface.
The dedicated athletes at the forefront of the sport have pushed back the horizons of the possible and broadened greatly our understanding of human aquatic potential. But at Apneista.com we don’t believe that free-diving should be seen as an extreme sport. We believe free-dive training can be better understood and enjoyed as a conscious re-tracing of our evolutionary foot steps, a joyful rediscovery of our aquatic heritage, more like yoga of the ocean than a competitive sport.
Wonderful. Very interesting post. Keep up the good work.