The Most Famous Extinction - National Geographic

A nice and neat morality fable, worthy of Aesop, but even Lull was perplexed by inconsistencies in the story. Dinosaurs persisted for a great span of Earth history, and some of the largest and most extravagant forms – such as Stegosaurus and the 80-foot, long-necked, small-skulled Brachiosaurus – lived right in the middle of the so-called Age of Reptiles, only to be replaced by dinosaurs such as Tyrannosaurus and Triceratops that were just as enormous and weird. What researchers thought of as the dinosaurian interlude – a long intermission where reptiles unjustly kept our mammalian ancestors and kin down – stretched on far long than would seem probable for animals believed to be victims of their excess. “[T]he marvel is, not that [the dinosaurs] died,” Lull observed, “but that they survived so long.”

In time, the self-destructive tendencies Lull and other researchers toyed with were recognized as fantasy and the undirected, unpredictable influence of natural selection became established as the prime force behind evolutionary change. Yet the mystery of dinosaur extinction remained, and the puzzle became a fertile playground for anyone with a notion for why they disappeared. By the middle of the 20th century, the question of the great dinosaur disappearance was open to all comers. Paleontologist Michael Benton has rightly called this the “Dilettante Phase” of dinosaur extinction studies, when any armchair expert of whatever discipline could forward their pet notion for the Mesozoic calamity.

As they had been since the early 20th century, dinosaurs were still viewed as aberrations that ruled the planet for an unjustly long amount of time. And instead of being broken down from within, they were thought to have been brought to their knees from without – too stupid, slow, and large to adapt and survive. Mammals clearly had the right qualities to persist and thrive in a changing world. Else we wouldn’t be here to mull over all this history. Then again, depending on who you asked, dinosaurs might have been wiped out by lack of sex drive, cataracts, the climate getting too hot, the climate growing too cold, radiation from a nearby supernova, and, perhaps most imaginative of all, slow starvation after caterpillars ate all the Mesozoic plant life.

Researchers inside and outside of paleontology continued to spin wild ideas as dinosaurs at long last received a major makeover in the 1970s and 80s – the “Dinosaur Renaissance.” This major pulse in argument and research was spurred by Deinonychus – a roughly human-sized, bird-like, switchblade-clawed carnivore of the same archetype as Jurassic Park’s villainous Velociraptor. Yale paleontologist John Ostrom, who described the Cretaceous predator in 1969, could not believe that such a lithe, menacing predator was an idiotic tail-dragger (least of all because Deinonychus had a tail stiffened by specialized tail bones, creating a sturdy counterabalance for the rest of the carnivore’s body). And as this dinosaur changed perceptions about what dinosaurs were, the conundrum of dinosaur extinction became stranger still.

The time had come to follow through with an idea that researchers had been toying with for decades – maybe dinosaurs weren’t actually sluggish reptiles writ large. Perhaps their biology and behavior were more unusual than anyone had supposed, and, based on the similarities between Deinonychus and Archaeopteryx (the earliest known bird), dinosaurs emerged as the best candidates for avian ancestors. And if birds could be counted as living dinosaurs, maybe avian traits – such as feathers, a hot-running metabolism, parental care – originated among creatures like Apatosaurus. In time, fossil discoveries and analysis of old bones would make dinosaurs far more bird-like than previous generations of researchers could have anticipated.