st of tive. Indeed, ile, it  time to be small, urnal, flexible indiet, and cautious by nature—ties t distinguished our mammalian forebears.

    ion been more advanced, ead,mammals found to hing alive.

    as if mammals so fill every nicion mayabe t Steven M. Stanley, “but it often takes a long timeto fill it.” For peren million years mammals remained cautiously small. Intertiary, if you  you could be king.

    But once t going, mammals expanded prodigiously—sometimes to an almostpreposterous degree. For a time, tory ory cen literally) to fill it. Early members of ted to Souto creatures ty of bears. Birds, too,prospered disproportionately. For millions of years, a gigantic, fligitanis  ferocious creature in Nortainly it  daunting bird t ever lived. It stood ten feet   could tear tty muc irked it. Its familysurvived in formidable fasy million years, yet until a skeleton  ed.

    o anotainty about extinctions: triness oftouc of bones becomingfossilized, but tually  think. Consider dinosaurs.

    Museums give t  Diplodocus t dominates trance ural ory Museum in London and ed and informedgenerations of visitors is made of plaster—built in 1903 in Pittsburged to trance ural oryin Need by an even grander tableau: a skeleton of a large Barosaurusdefending tack by a darting and toot is a y feet to alsoentirely fake. Every one of t. Visit almost anylarge natural ory museum in t, Buenos Aires,Mexico City—and  you are antique models, not ancient bones.

    t is,  really