THE FIRST FEW hundred yards are easy. My heart settles in; my body adjusts. The sea is so sparkly, I feel like a diamond in a glittering field. The goal seems so tiny, I feel like a ship without radar. But oddly, I feel at home here in the Hellespont. What, I can’t help wondering, might I say if someone were to ask how I’m doing? The answer, immediately, is both surprising and simple: swimmingly.
We were fish ourselves hundreds of millions of years ago, awash in the liquid where life evolved.
“The fish part of us is really very deep, and it’s written inside of the basic structure of our bodies,” explains evolutionary biologist Dr. Neil Shubin of the University of Chicago. He led the team in 2004 that found the missing link between our aquatic ancestors and land-based mammals—a 375-million-year-old fossil fish that emerged from the water to breathe air. Its anatomy captures the transition to future species while reflecting the heritage of its past: “Our basic structure is actually first seen in fossil fish. They are the first creatures with skulls like ours. And the genes that make that, the bits of DNA that build our own body, are actually versions of those seen in building the same body plan in a fish. At some levels we’re extremely similar genetically to fish.”
I have come to Chicago to meet Dr. Shubin in his anatomy lab, a warren of workbenches and fish models where scholars continue to mine the riches of his discovery. He has filled a critical gap in the evolutionary story and, with the sharp wit and sense of wonder that define our most engaging scientists, has agreed to help me explore the human connection—biologically, evolutionarily—to the water. We begin with the creature he found in the Canadian Arctic, a pioneering voyager from the primordial pool named Tiktaalik (“large freshwater fish”) in the language of the local Inuit. The model that I see—from just one of many retrieved fossils that range up to nine feet long—is about the length of my arm: a long-bodied, low-finned fish with a placid smile on a face I can only describe as sweet. “Isn’t that cute?” Dr. Shubin asks me, clearly pleased with his treasure. “The first thing we saw was the snout. It was upside down, sticking out of the cliff like this,” he says, flipping the model and grasping it in his hands.
Beneath Tiktaalik’s grin lurked the sharp fangs of a predator on the way to making biological history, a hardy émigré armed with features adapted for life outside the water: a neck that allowed its head to swivel, critical for excursions on land, where you can’t flip your body at will; a flat skull like a crocodile’s with eyes on top, the better to see terrestrial prey; lungs that can process air; and articulated bones embedded in its front fins that enabled it to climb out of the past. “Clearly they were able to support their bodies with their fins, like doing a form of a pushup,” Dr. Shubin tells me, reaching for a model of the fin and pointing to its stubby little projections. “There’s the elbow; there’s the wrist. So it functions like a fin—it could paddle around—but it could also support the body. What’s really cool are these bones that correspond to ours: this is the radius; this is the ulna; here’s the shoulder.” The entire fin is about the size of my hand. It is the predecessor of my upper arm and forearm, with distinct joints at the shoulder, elbow, and wrist—all that, in addition to the same gills, scales, and webbing as today’s fresh halibut lying on ice chips at my local seafood shop.
In other words, undeniable evidence of what Dr. Shubin calls a “fishapod”—a perfect mix of a fish and a tetrapod, or four-legged land creature. Somewhere along the evolutionary tree, someone with appendages like these veered off onto a limb to help establish everything from dinosaurs to humans.
“You know, every time you bend your head or bend your wrist—and there are other functions as well—these are fish functions that originally appeared in fish living in aquatic ecosystems,” he says. In addition, our ears are modified gill bones; a human fetus has gill slits. In sum, “the tool kit that builds our bodies is a version of that which builds a fish.”
Which fish?
Dr. Shubin says we humans are closest in terms of anatomy and DNA to lungfish or, lower down what he calls the “tree of cousinness,” to sturgeon or paddlefish. Drop further, and it’s sharks or shark-like creatures. And way down, the invertebrate predecessor to the fish: the worm. Time to expand the family photo album? “The odds of [Tiktaalik] being our exact ancestor are very remote,” Shubin writes in his lively and enlightening book, Your Inner Fish. “It is more like a cousin of our ancestor.” So why don’t we talk about our connection to fish? How come we only acknowledge the great apes? “I don’t know,” he concedes to me. “It’s not something that’s so obvious to people. Some people have a hard time accepting our relationship to monkeys. Well, it’s the worms you need to worry about.”
We don’t even own the bragging rights to the biggest talent separating us from water dwellers. “Air breathing originally evolved in fish that lived in anoxic waters, waters that were depleted in oxygen,” he explains. I think about the brilliantly colored koi slithering around in my fish pond back home: sometimes on hot days, they swim along, reach up, “take a big gulp of air, and come back down,” says Shubin, finishing my thought. “Lungs actually are ancient. Air breathing is a fishy thing.”
Why it developed—and why the quest for even more air lured Tiktaalik and its pals out of their comfort zone in the water back in the late Devonian age—is not clear. Possibly for food, where there were fewer competitors. Possibly to escape prehistoric marine predators. But it wasn’t all that they had hoped for: some creatures returned to the water after a time. I ask whether we, today’s swimmers, are doing the same.
“In evolutionary terms? No,” says Dr. Shubin. “But water is something that is very magical to us. Not because of our anatomy—it’s really because of our psyche, the way we see the world. It’s the way our brains are wired. Look, I have little kids, and it’s hard to pull them out of the pool. We have a natural affinity to water.”
Shubin does not accept the Aquatic Ape theory—a tantalizing but controversial hypothesis that humans evolved from a branch of apes who had adapted to life in the water. One claim of evidence: the vestigial webbing that connects our fingers.
“Nobody buys it,” he says, speaking for the paleontology community and shaking his head. “Because we really don’t have that evidence in our fossil record. It almost makes more sense that we are derived to run on land. That doesn’t mean that we’re just one-trick horses. We can use those aerobic abilities to swim in water too. I mean, what’s great about humans is that we can inhabit almost every environment, right? We’re a species that is amazingly variable.”
Fish swim because they have to; we do it by choice. Some fish can climb trees and glide through the air; so can we, with proper training and appropriate equipment. And even if our aquatically rooted anatomy doesn’t explain our need to swim, the flexibility we inherited sure makes it easier. For starters, our bodies are mostly made of water which, when you think about it, makes the water we swim in a far less hostile environment. President John F. Kennedy made the connection in a speech about sailing: “All of us have in our veins the exact same percentage of salt in our blood that exists in the ocean, and, therefore, we have salt in our blood, in our sweat, in our tears. We are tied to the ocean. And when we go back to the se. . . . we are going back from whence we came.”
Thanks to Archimedes, we understand the principles that make it possible. His Eureka! moment in the bathtub 2,000 years ago in ancient Syracuse may have been apocryphal, but it nonetheless provides a useful illustration of the science that keeps us afloat. All that water spilling over the sides when he lowered himself into the tub revealed the connection between displacement and buoyancy, which is actually a function of density: anything denser than water will sink; less or the same will bob around like a cork. That’s us. The human body has almost the same density as water (a ratio that’s called specific gravity), a nifty trick of physics that lets us glide on the waves and slide through the surf. Buoyancy makes water a mystical medium: it allows us to weigh less, to feel as if we’re flying, to forget about gravity. If it worked on dry land, it would put plastic surgeons out of business; in the water, it is nature’s personal swim aid, a no-cost reward for getting wet. And it’s enhanced by salt, which is why we float more easily in oceans. When there’s an extreme amount—as in the Dead Sea, where salt comprises 35 percent rather than the usual 3 percent—you’re so buoyant, you can barely move. The Roman historian Tacitus described the ancient site this way in the second century CE: “These strange waters support what is thrown upon them, as on a solid surface, and all persons, whether they can swim or not, are equally buoyed up by the waves.” When I visit the Dead Sea in Israel, my guide puts it more bluntly before I venture in: “As soon as your backside touches the water, you’re floating.” No kidding. Swimming is impossible; turning on your belly makes you feel like a beetle flipped on its back—your legs pop skyward, unaided, and standing upright is a struggle.
Benjamin Franklin used buoyancy to help conquer fear. “You will be no swimmer till you place some confidence in the power of the water to support you,” he advised a nonswimming friend in a letter during the late 1760s. How to do it? In a pond or stream where the water deepens gradually, walk in, up to your chest, and then turn to face the shore. Next, toss a boiled egg into the water—toward the shore—and when it sinks, dive in and try to grab it. “You will find,” Dr. Franklin writes, “that the water buoys you up against your inclination; that it is not so easy a thing to sink as you imagined; that you cannot but by active force get down to the egg. Thus you feel the power of the water to support you, and learn to confide in that power; while your endeavours to overcome it and to reach the egg, teach you the manner of acting on the water with your feet and hands.”
And then you get to eat the egg.
Buoyancy also lifts the ego when other body parts start to droop. Curvy people float better than lean beans, and women more than men, because even at our slimmest, we have an extra layer of fat distributed throughout our bodies. The scientific term is positive buoyancy, which sounds a lot better than, say, “solid” or “chunky.” Wiry guys, and probably some gals, have negative buoyancy, which sounds a lot better than “skinny.” Their legs, or entire bodies, go down faster. Most of us are either one or the other. The great long distance swimmer Lynne Cox was born smack in the middle. In her lyrical memoir, Swimming to Antarctica, Cox writes about learning that she has “neutral buoyancy. That means,” her doctor told her, “your body density is exactly the same as seawater. Your proportion of fat to muscle is perfectly balanced so you don’t float or sink in the water; you’re at one with the water. We’ve never seen anything like this before.” She meant: in a human. For Cox (whose awesome exploits receive the attention they deserve in Chapter 6), that biological oddity meant “that I didn’t have to use energy to either fight against sinking or pull myself down into the water to counteract buoyancy. This enabled me to swim more efficiently.”
Can Giraffes Swim?
It’s not the sort of question you can ask a giraffe. And no human has ever reported seeing one take a proper dip. One herd was caught on video wading into the water chest high, but they retreated to shore as the bottom dropped off. The issue isn’t size—elephants are graceful swimmers—but shape, which seems to defy the laws of aquatics: up to two tons of bulky mass offset by a flexible tower of a neck, perched atop four formidable legs of two different lengths. Can its lungs, notoriously oversized, hold enough oxygen to enable flotation? Two imaginative paleontologists created a computer model, complete with spots and the little “horns” known as ossicones, and plunked it into the digital drink. Factoring in the effects of drag and density, they found that the giraffe’s shorter hind legs would float before its front legs; that in deeper water, it would start to angle downward until its neck rested on or below the surface; that it wouldn’t sink but would look “downright uncomfortable.” And since it couldn’t use its neck to pump up its gait (as it does on land), it likely would be a “very poor” swimmer. Their conclusion: “giraffes can swim, but not at all well.”
For ardent giraffe lovers like me, knowing they’re landlubbers is just fine. For radio host Peter Sagal, the results are more troubling. “You might wonder who might fund such a study,” he mused on NPR’s Wait Wai. . . . Don’t Tell Me. “Turns out it was a pack of hyenas.”
Understanding the science of our connection to the water is both instructive and reassuring. But that’s just the first step. Discovering the effect that water has on our bodies upgrades swimming from a pleasant pastime to a medical must, although the about-face of the medical community since the Middle Ages has led to some, shall we say, exaggerated claims. More than five hundred years ago, Reverend Digby recommended swimming for “purging poisoned humors, drying away contagious diseases, and by this means adding longer date unto the life of man.” Time only heightened the hype. A French physician in 1819 said swimming cured everything from masturbation to pulmonary infections to spontaneous dislocation of the femur. Two decades later, a popular handbook called British Manly Exercises promised would-be jocks that it was also “useful i. . . . the tranquilizing of the nervous system.” Around the same time, an American identifying himself only as “An Experienced Swimmer” wrote that swimmers “are not liable to sudden colds, or inflammatory diseases and rarely if ever, suffer from chronic complaints. Their bodies become indurated, their skin is healthy, and all the functions of life are carried on with healthful vigor.” A YMCA manual capped it off in 1910 with the claim that swimming outdoors “prevents the growth of gray hair.”
If only. Swimmers are hale, not disease-proof; hardy, not ageless. But a century—or five—later, there are alluring indications that regular, vigorous water activity may indeed extend human life. Every time we grind out our laps, we may, in some measure, be swimming in the fountain of youth. The proven benefits read like a wish list from the American Heart Association: swimming can lower blood pressure and optimize cholesterol levels, improve the pumping capacity of the heart and thus enhance circulation, expand the ventilator capacity of the lungs and thus enhance cardiovascular performance. One celebrated study found that mortality rates for swimmers were lower than for those who are sedentary, walkers, and runners.
Cousin Tiktaalik’s push-ups were just the beginning; swimming is a rhythmic, dynamic activity that uses every large muscle group. It helps build lean muscle mass and promote flexibility. And while it’s true that all aerobic exercise leads to many of those results, a recent study shows that swimmers bested joggers and walkers in every cardio number. More significant for a nation with an aging population, you don’t hear complaints about bone spurs in the pool. “Swimming is the closest thing on this earth to a perfect sport,” writes Dr. Jane Katz, a pioneering swim fitness promoter and educator.
Movie star Esther Williams has often said, “Swimming is the only thing you can do from your first bath to your last without hurting yourself. When you’re in the water, you’re weightless and ageless.”
No knees pounding the pavement. No joints slamming against a ball or a wall. Buoyancy protects the most vulnerable parts of our skeleton. Just ask a pregnant woman. “Suddenly that big bump becomes weightless,” rhapsodizes a young mother recalling her blissful Caribbean swims at five months along.
For people with certain disabilities swimming feels like a miracle. Byron was born with a club foot, a contracted Achilles tendon that gave him a pronounced and debilitating limp. In the water, he moved like an eel. “I can keep myself up for hours in the sea,” he wrote. “I delight in it, and come out with a buoyancy of spirits I never feel on any other occasion. If I believed i. . . . transmigratio. . . . I should think I had been made a Merman in some former state of existence.” Annette Kellerman, the Australian swimmer who helped usher American women into the water with well-publicized endurance swims and sexy films, wore heavy iron braces on her legs as a child, the result of some sort of bone ailment. Swimming lessons turned her into a mermaid.
I started swimming in earnest after recovering from a broken kneecap in 1977, when eight weeks in a full-leg cast left my joint immobile and my quadriceps withered. Regular laps helped restore both muscle and flexibility. Since then, I’ve expanded my workouts to the rest of my body, adding weight training and Pilates in a weekly regime. I was in reasonably good shape before I began my Hellespont training. But the water upped the ante.
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