omplexorganisms, t four million years—rougwhere we are now.
Extinction is alims, of course, but it appears to be a good t. “ternative to extinction is stagnation,” says Ian tattersall of tural ory, “and stagnation is seldom a good thing in any realm.”
(I se t ion as a natural, long-term process.
Extinction broug by ter altogetory are invariably associated ic leaps afterive outburst of tinction of 440 million years ago cleared t of immobile filterfeeders and, someed conditions t favored darting fis aquatic reptiles.
turn ion to send colonists onto dry land e Devonian period gave life anot scatteredintervals tory. If most of ts as t ainly be here now.
Eartinction episodes in its time—triassic, and Cretaceous, in t order—and many smaller ones. t about 80 to 85 percent ofspecies. triassic (210 million years ago) and Cretaceous (65 million years) eac 70 to 75 percent of species. But tinction of about 245million years ago, least 95 percent of animals kno, never to return. Evenabout a t species —t en masse. It isas close as otal obliteration.
“It ruly, a mass extinction, a carnage of a magnitude t roubled tey. t icularly devastating to sea creatures.
trilobites vanisoget. Virtually all otaggered. Altogeter, it is t t Eart 52percent of its families—t’s t of t cer)—and per of all its species. Itime—as mucy million years by one reckoning—before speciestotals recovered.
ts need to be kept in mind. First, t informed guesses. Estimates fort toas knoion t perisalking about t individuals. For individuals toll could be mucically total. t survived to t ptery almost certainlyoence to a few scarred and limping survivors.
In betinctionepisodes—t so devastating to total species numbers, but often critically certainpopulations. Grazing animals, including in t about five million years ago. o a single species, t for a time it teetered on tory grazing animals.
In nearly every case, for botinctions and more modes