National Geographic : 2018 Mar
FROM LEFT: ROMIP SPECIMEN 64529; SPECIMEN FROM FLORIDA KEYS MARINE LIFE PHYLUM ECHINODERMATA AN ENDURING DESIGN Like more familiar echinoderms such as sea stars and sea urchins, the Ordovician sea lily above and modern basket star at right have a body plan arranged symmetrically around a central mouth. Fixed to the bottom by a stalk, the sea lily fed by gathering particles from the water with its arms and bringing them to its mouth. Four hundred fifty million years later, the basket star employs much the same strategy, spreading its profusion of armlets to filter as much water as possible. Most experts would agree that smartness, even on a level expressed by a primitive worm, wasn’t a wrench in the Ediacaran tool kit. Those creatures’ genomes may have been coded for fractal repetition—at least in the rangeomorphs, where it yielded a simple sort of complexity—but not for responsiveness to circumstances, or effi- ciency. Still, it’s a mistaken point to dismiss the Ediacarans as doomed. People made that error with the dodo, when they branded it an emblem of ill-fated stupidity. But the real dodo, Raphus cucullatus, a large, flightless, fruit-eating bird endemic to the island of Mauritius, had thrived in its peaceable home for many thousands of years—until Homo sapiens and other predators arrived. Likewise the Ediacarans, with their own new threats. You can call them “failed experi- ments” in evolution if you want, but they suc- ceeded and flourished, within their preferred but challenging environments, for more than 30 million years. We humans should be so steadfast and lucky. j Contributing writer David Quammen’s next book, The Tangled Tree, will be published by Simon & Schu ster in September. Photographer David Liittschwager has been illuminating the elegance and beauty of the natural world for National Geographic since 2005.