A Billion Heartbeats
A billion heartbeats is the limit, but the human brain is the game-changer.
Have you ever thought how many heartbeats you have left before you die? In 2004, mathematician and theoretical physicist Geoffrey West arrived at the Santa Fe Institute (SFI). Dr. West soon begin to think about the beats of his heart. He knew everything dies; the question is how fast? He also knew the cells of a body are the room housing the mitochondria, the prodigious metabolic motor. The process by which carbohydrates are converted into energy is known as the Krebs Cycle. In 1837, physician Hans Krebs, a later to be Nobel Prize winner, discovered that carbon dioxide rolls down the energy hill releasing energy and picking up carbon along the way. The result is that all species have the same conceptual blueprint.
Species have completely different life spans though. Tortoises and whales live more than two hundred years; a shrew lives about two years, a redwood tree a thousand years, and a fruit fly a month, a rhino fifty years, a gazelle twenty years. Why?
To answer this question Dr. West started with the 1930s work of Swiss-born chemist Max Kleiber. The Kleiber Ratio is that for every creature, the amount of energy burned per unit of weight is proportional to that animals mass raised to the three-quarters power. That means smaller takes more calories per pound to stay alive, while larger takes less calories per pound to stay alive. The pattern is of increasing efficiency.
The answer to the length of life turned out to be the faster the heartbeat, the shorter the life, the slower the heartbeat, the longer the life. The pattern discovered is that in general all amphibians, birds, fish, mammals and reptiles have roughly a billion beats per lifetime. Whales’ heartbeats average 10-15 a minute, even slower while diving, shrews 850 beats a minute, even faster to 1,500 when frightened. Human’s hearts beat at around 70 a minute. That means humans shouldn’t be living past young adulthood. The reason humans are the sole exception to the rule is our big brains that have figured out how to bend the rules.
Dr. West discovered that Kleiber Ratio’s is universal: “There’s this exquisite interconnectivity. All the structures have different forms and functions, but all of them adhere to the same scaling pattern.” Capillaries grow into veins and arteries according to the same three-quarter-power scale. So also do neural fibers by becoming whole nerves then becoming nerve bindles. From the mitochondria to the cell to the blue whale, the rule holds through twenty-seven orders of magnitude. That’s 1 x 10 = 10, 10 times 10 = 100, 100 x 10 = 1,000 until repeated an incredible twenty-seven times. That is 1,000,000,000,000,000,000,000,000,000.
Nobel Prize winning physicist Murray Gell-Mann, also of SFI, said “We don’t know why this is such a common power law. We’re already looking at simplified computer models to better understand how such a pattern could occur in nature.”
The answer to why this scale is universal though is known. It is because organic and non-organic operate on similar principles. Eric Smith, also of the Santa Fe Institute, says all emerged from the geological processes, “Metabolism is a complicated science but it’s also the one in which the rules are most like that of geochemistry.” Jeffrey Kluger, in his book Simplexity, wonders about the same overlap into cities. He wrote, “There’s an odd cellularity of a city glimpsed from an airplane window at night, a splatter of light resembling nothing so much as a brain cell. With the axons and dendrites of highways connecting to the other cells other cities nearby. There’s the vascular nature of highway systems the biggest roads even given the name of “arteries” with individual vehicles bumping along like little blood cells . . .” Coincidence? Does the Kleiber Ratio apply to cities? According to Dr. West’s studies it does. Cities also conform to the same mass-to-the-three-quarters-pattern. Cities also are calibrated to conserve energy. Instead of calories, the measurement is money, material or labor. Like the larger animals requiring lessor energy per pound, larger cities also require less energy per block. “Cities, despite their appearance, satisfy the rules of biology,” says Dr West. The population size of cities also follows Zipf’s Law.
Zipf’s Law is another interesting pattern. In 1932, George Kingsgley Zipf wondered about the frequency of words and terms turning up in texts. Being a Harvard University linguist, he began to count them. He discovered the pattern determining how often words are used. The most common words, like “the” appear twice as much as the next common words. Third-place words appear a third as often as the number one common words. Fourth-place words appear a fourth as often as the number one common words. And on. This pattern is also in incomes, the size if corporations and in urban population sizes. America’s largest city in 2006 was New York, with 8.14 million people, Los Angeles placed second at 3.84 million people, and Chicago placed third at 2.84 million people. Houston was fourth at 2.02 million; Philadelphia was fifth at 1.46 million. That population pattern roughly follows Zipf’s Law.
The patterns in all this exquisite interconnectivity increase efficiency because they extract more energy and output per individual component. The result of the discoveries has been a new profession, one known as complexity researchers, with a whole new seemingly simple but highly adaptive layered landscape to explore.