Today in the Sixth Extinction
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After humans finish with the Sixth Extinction, presumably ending in our own species going extinct, what will the planet look like? Probably filled with small creatures:
From sharks to giraffes, many of Earth’s biggest and most magnificent species are threatened with extinction. A new study of the fossil record indicates that once large vertebrates disappear, evolution cannot quickly restore them — for tens of millions of years, most animals remain small.
The study, published Thursday in Science, emerged from research carried out by Lauren Sallan, a paleontologist at the University of Pennsylvania.
Studying fish that lived during the Mississippian Period, from 359 million to 323 million years ago, she noticed that they were substantially smaller than their ancestors.
“It piqued my curiosity,” Dr. Sallan said in an interview. “Why are these fish so small?” (She earned a nickname from her fellow paleontologists: the Sardine Queen.)
Other paleontologists had previously noticed that some groups of species seemed to shrink in size over time. It’s called the Lilliput Effect, after the fictional island in Jonathan Swift’s “Gulliver’s Travels” inhabited by tiny people.
Researchers found that the Lilliput Effect often occurred after abrupt and widespread extinctions. Dr. Sallan’s fish appeared to fit the pattern: They shrank after a mass extinction at the end of the Devonian Period, 359 million years ago.
Likely this means that house cats complete their takeover of the world, probably assisted by their jellyfish allies in the ocean.