When I was a young girl over half a century ago (I just blinked as I wrote that phrase!), two of my interests were birds and dinosaurs. Little did I suspect then that over the ensuing decades most scientists would come to believe that the two are inextricably linked, that birds evolved from dinosaurs around 150 million years ago. Today scientists consider birds “avian dinosaurs,” and, as such, our avian friends are the sole dinosaur survivors. (Crocodiles and alligators survived from the same era, but scientists consider them dinosaur “cousins.”)
Birds emerged from a dinosaur group called therapods, and myriad similarities link the two. Birds have reptilianlike scales on their feet, and their featherproducing tissue is akin to scaleproducing tissue. Birds and reptiles both lay eggs, and fossil remains suggest that dinosaurs exhibited brooding behavior like that of nesting birds. Additionally, many skeletal and softtissue similarities link birds and dinosaurs, such as hollow bones and gizzard stones. Most striking, perhaps, are fossils of twenty different kinds of dinosaurs that show evidence of feathers.
One of the most famous fossil remains is that of Archaeopteryx, which dates from 150 million years ago. Some scientists consider Archaeopteryx to be the transitional form between dinosaurs and birds. The fossil remains illustrate that this creature had feathers, a wishbone and reduced “fingers,” all characteristics of modern birds.
Most recently scientists have shown that modern bird skulls bear a marked resemblance to baby dinosaur skulls and crocodilian skulls (The New York Times, 5/31/12). Dinosaur skulls elongated as the animal matured, leaving less room for its brain and eyes, just as happens with crocodiles. However, in primitive birds the skull retained its juvenile dinosaurlike shape even as the body grew, thus allowing more cranial space for the keen eyes and larger brain necessary for sharp vision and quick action.
Indeed, the pejorative phrase “bird brain” seems quite inaccurate since birds are capable of astonishing feats. The peregrine falcon can spot distant prey and drop 200 milesanhour from 3,000 feet as it zeroes in on its unlucky victim. Crows leave gifts for people who feed them and strafe, day after day, those to whom they’ve taken an aversion. Robins can hear an earthworm’s tiny bristles as the worm rubs against its burrow. Some birds migrate extraordinarily long distances, a few species as much as 10,000 miles, using the stars, topographic cues and the earth’s magnetic system to guide them.
Today there are over 9,000 kinds of birds, fascinating to observeand a link to the very distant past when dinosaurs ruled the earth.
