10. A lifespan is a billion heartbeats. Complex organisms die. Sad though it is in individual cases, it’s a necessary part of the bigger picture; life pushes out the old to make way for the new. Remarkably, there exist simple scaling laws relating animal metabolism to body mass. Larger animals live longer; but they also metabolize slower, as manifested in slower heart rates. These effects cancel out, so that animals from shrews to blue whales have lifespans with just about equal number of heartbeats — about one and a half billion, if you simply must be precise. In that very real sense, all animal species experience “the same amount of time.”Humans seem to be the exception to this rule; our species is generally allotted something closer to 3 billion heartbeats over a lifespan of roughly 80 years (at least here in the Western world). At any rate, this made me think of Gary Fincke's poem "The Billion Heartbeats of the Mammal" which you owe it to yourself to read.
"Feel this," my father says, guiding my hand To the simple braille of his pacemaker. "Sixty," he tells me, "over and over Like a clock," and I mention the billion heartbeats of the mammal, how the lifespan Can be rough-guessed by the 800 beats Per minute of the shrew, the 200 Of the house cat, speeding through their billion In three years, in twelve. How slowly we act, According to our pets. How we are stone To the frantic insects. "The hurry-up To nowhere," he says, working out the math, Busy with wiping down linoleum The way he swirled a mop through locker rooms Before striding the push broom up and down The grain of gym sweep, repeating the moves Of twenty kinds of cleaning between ten And six-thirty in the high school I used Between eight and three-fifteen. He might have Been following the Peterson Method For care, learning the neat lines and ovals Of my mother, who wrote to me, the day She died, a perfectly scripted letter, Pages of open vowels so nothing She said could be misread. And even now, In the attic, inside her black notebooks Stacked and banded, her carefully copied Familiar quotes, the good advice Of the writing exercise dating back To a hundred lines of ovals, fifty Of the properly slanted line. Penciled Pages of strict, block printing, the two-space Capitals, the touch of the tall letters To the roof of lines, my father finding By multiplication and division, The thirty years of the human, how he is Closing in on three billion while I am Nearing two. How we are the exception To the heartbeat system, taking so long To come of age we have time to practice The Peterson Method for memory, Preserve these things to open up and read.
It occurs to me that being about a month shy of 30, I have just about exhausted my first billion heartbeats. Here's to the next two billion.