the largest creatures that ever lived -- 7/28/21
Today's selection -- from Spying on Whales: The Past, Present, and Future of Earth's Most Awesome Creatures by Nick Pyenson. Blue whales are the most massive animals in Earth's history:
"Take in a deep breath. And now relax. You just shared oxygen with the largest animal -- ever, in the history of life on Earth. In a single blow, this animal expels a column of water vapor that would reach the top of a two-story house; the air that passed through its lungs is enough to fill half a cement-mixer truck. Its blood cells pass through a heart with vessels the diameter of dinner plates and run through a body with over twenty billion miles of arteries, capillaries, and veins. Blood must carry oxygen to every cell in this animal -- all 1,000 trillion of them -- including nerves whose fibers reach over one hundred feet from its brain stem to every extremity, including its tail fluke. With a flip of its fluke, the animal descends to a depth beyond the limits of light, where it makes the most acoustically powerful sound made by any organism, a low tone that spreads for over nine hundred miles, echoing off undersea canyons. Everything about this animal, in all the ways that we can measure, is superlative. This animal is, of course, a blue whale.
"Extremes enthrall us all, and the idea of an ultimate size champion among living things is a captivating thought. Ask an elementary-school kid about the biggest animal of all time, and the short list of possible contenders very quickly becomes a battle between two titans: a blue whale versus a sauropod dinosaur. This comparison is enshrined in textbooks, usually with a stylized composition of a blue whale, midgulp, floating above a sauropod, sloping neck and tail extending in opposite directions. Sometimes you might see a string of African elephants or school buses for scale.
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"The winner of this runoff, of course, depends a bit on how you measure the contestants. The longest of the sauropod dinosaurs probably exceeded 110 feet in total length, based on relatively complete skeletons. That linear distance comes close to the longest blue whale ever measured -- a 109-foot female from the Southern Ocean, killed in 1926 by Norwegian whalers. But whales are the true heavyweights. At most, the largest sauropods might have weighed 120 tons, but the best estimates place the largest ones closer to 70 tons. By comparison, the heaviest blue whale reliably measured (a female, also from the Southern Ocean) weighed 136.4 tons, or just over 300,000 pounds more than the takeoff weight of a Boeing 757. And this particular whale was only an eighty-nine-foot-long female. A blue whale closer to one hundred feet, especially if pregnant, would have weighed much more. From the standpoint of biomass, it's not much of a contest: blue whales are the most massive animals ever in the history of life, and we just happen to live along-side them.
"For us, a whale's size may be the most striking thing about them, but the fascination is not just about sheer bulk. How can a creature of that magnitude keep itself alive? Size determines a lot about how much air a whale needs, how deep it can dive, how much food it needs to eat, and how far it can swim. But step back for a moment from these physiological questions: How did whales become giants in the first place? We know the beginning and end points: within the fifty million years that took whales from land ancestry to dominance in the oceans, the weight difference between Pakicetus and a blue whale increased about ten thousand times. How exactly did this change unfold? And how can we know?"
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