In Brief
- The descent of birds from small, meat-eating dinosaurs is by now established. Far less clear is the origin of anatomically modern birds.
- The conventional fossil-based thinking is that modern birds arose only after the asteroid impact that claimed the dinosaurs and many other creatures 65 million years ago.
- But molecular studies and a smattering of equivocal fossil finds have hinted that modern birds might have deeper roots.
- Recently analyzed fossils of ancient modern birds confirm this earlier origin, raising the question of why these birds, but not the archaic ones, survived the mass extinction.
December in Moscow, and the temperature drops under 15 degrees below zero. The radiators in the bar have grown cold, so I sit in a thick coat and gloves drinking vodka while I ponder the fossil birds. The year is 2001, and Evgeny N. Kurochkin of the Russian Academy of Sciences and I have just spent hours at the paleontology museum as part of our effort to survey all the avian fossils ever collected in Mongolia by joint Soviet-Mongolian expeditions. Among the remains is a wing unearthed in the Gobi Desert in 1987. Compared with the spectacularly preserved dinosaur skeletons in the museum’s collections, this tiny wing—its delicate bones jumbled and crushed—is decidedly unglamorous. But it offers a strong hint that a widely held view of bird evolution is wrong.
More than 10,000 species of birds populate the earth today. Some are adapted to living far out on the open ocean, others eke out a living in arid deserts, and still others dwell atop snow-capped mountains. Indeed, of all the classes of land vertebrates, the one comprising birds is easily the most diverse. Evolutionary biologists long assumed that the ancestors of today’s birds owed their success to the asteroid impact that wiped out the dinosaurs and many other land vertebrates around 65 million years ago. Their reasoning was simple: although birds had evolved before that catastrophe, anatomically modern varieties appeared in the fossil record only after that event. The dawning of ducks, cuckoos, hummingbirds and other modern forms—which together make up the neornithine (“new birds”) lineage—seemed to be a classic case of an evolutionary radiation in response to the clearing out of ecological niches by an extinction event. In this case, the niches were those occupied by dinosaurs, the flying reptiles known as pterosaurs and archaic birds.
This article was originally published with the title Winged Victory.
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3 Comments
Add CommentWhen I read Dr. Ward's Out Of Thin Air, it seemed obvious to me from the evidence presented in the book that bird evolved in response to the catastrophe erasing life on the Earth at the end of the Triassic. Hard time actually making life more efficient. Bird mitochondria leaks far less than ours. They utilize their urea. Now we all have bird envy.
Reply | Report Abuse | Link to thisWhat do you mean when you say mitochondria leaks?
Reply | Report Abuse | Link to thisDr. Dyke, does is sound reasonable to conjecture that the ancient birds, based on their having teeth, were meat eaters? If that sounds reasonable, then is it plausible that when the asteroid hit 65 million years ago and wiped out the giant dinosaurs, it quickly depleted the world of a major food supply for those meat eating ancient birds? Would then seem logical that the ones to survive were those with a wider food supply of non-meat stuffs, such as the ducks you mention? Modern meat eating birds are often scavengers. If the ancient meat eating birds were scavengers, it would seem reasonable that they depended upon the remains of the large meat eating dinosaurs. Is there a way to determine 1) that ancient birds (the ones with teeth) were meat eaters? 2) that they were scavengers (like modern meat eating birds)? and 3) the world meat supply disappeared quickly after the asteroid hit?
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