Birds are dinosaurs. “This is one of the greatest achievements in the history of paleontology,” writes Steve Brusatte, in his splendid new book, The Story of Birds: A New History from their Dinosaur Origins to the Present. Tracing the evolution of the idea of the bird-dinosaur connection, as well as the actual evolution of birds, Brusatte reveals a complex, layered story that justifies his statement. But I have to disagree slightly with him. Our understanding that birds are dinosaurs is not just a paleontological achievement. I would argue that it is one of the great achievements of science, illustrating a combination of geology, ecology, physics, and biology. Each of these fields, along with others, has helped provide the details that show the conclusive connection of these iconic animals.

As Brusatte writes, the idea goes back to the time of Darwin and Wallace and their fleshing out natural selection. Thomas Henry Huxley, often called Darwin’s bulldog for his defense of Mr. D, was the first (in 1868) to draw the link between our feathered friends and the biggest beasts of the past. Using his knowledge of anatomy, Huxley concluded that “the leg of a barnyard chicken is a miniature version of any T. rex leg you see in a museum,” writes Brusatte. In the middle 1800s few dinosaur fossils had been found so when Huxley made the connection, he was actually referencing a small, two-legged theropod (the group that includes Tyrannosaurus rex) known as Compsognathus. That lack of evidence was problematic because Victorian scientists, like their modern counterparts, couldn’t cotton to the bird/dinosaur connection without the facts.

Not until 1964 would the idea be revived, when paleontologist John Ostrom unearthed Deinonychus, a species unlike the prevailing image of dinosaurs. Instead of a lumbering, tail dragging, plodding lummox, Deinonychus were agile, active, fast, and formidable predators, he wrote. Ostrom based his description on the bones he found, which showed a lithe, long-limbed beast with sickle-like claws on each hand. (Deinonychus means terrible claw.) The fossils made him think of Archaeopteryx, a Jurassic Period fossil, long known as the oldest evidence for birds. When Ostrom compared the skeletons of the two species, it was clear, he concluded, that Archaeopteryx, with their classic avian feathers, had evolved from a theropod dinosaur, such as an ancestor of Deinonychus. The dinosaur-bird link was back, writes Brusatte.

Ostrom’s linkage of birds and theropods is a key point that Brusatte stresses. The family tree of dinosaurs is a phenomenally diverse group, persisting for hundreds of millions of years and ranging from chicken-sized, feathered, two-legged carnivores (e.g. Tyrannosaurus rex) to school-bus sized, four-legged plant-eaters (e.g. Brontosaurus). Birds are simply one limb of that tree, similar to the many branches of the mammal family tree. Comparing body shapes, one might not link bats, whales, apes, and anteaters, and yet we easily fit them in the same family. “A bird is a dinosaur version of a bat. A dinosaur that got small, evolved wings and developed the ability to fly but retains many hallmarks of its dinosaur relatives,” writes Brusatte.

Over more than 300 pages, Brusatte provides the thrilling evidence. For some, the most exciting is feathers. In 1996, exquisite dinosaur fossils with stunningly detailed feathers began to come out of China. As numerous additional species came to light, it confirmed the direct relationship between birds and dinosaurs; so feathered were dinosaurs that Brusatte could write “feathers were to dinosaurs what hair is to mammals: the default condition.” But feathers don’t mean that dinosaurs could fly or that all birds fly. Consider moas, emus, ostriches, and penguins; they gave up flight and kept their feathers, a subject that Brusatte describes in a wonderful chapter on earth-bound birds.

But birds are more than light boned (usually), winged, and feathered. They were the “intellectual champions among land-dwelling animals for many millions of years…[until] a few million years ago, perhaps, when some big-brained ape” came along, writes Brusatte. In addition, birds evolved the superbly adaptable beak, or what he describes as “revolutionary new inventions.” Birds are also fast growing; one reason you rarely see baby birds is that they simply mature too quickly. And, of course, birds vocalize, cacophonying the world with harmonies, tweets, chirps, honks, cackles, whistles, squawks, and screeches.

Brusatte’s writing is clear, concise, and up to date. Over the past few decades paleontology has become truly multi-disciplinary (as well as adaptive of new technology) and he appears to know everybody who is making it so. I particularly appreciate how generous he is in referring to and praising the stellar work of these other scientists. He also illustrates how paleontology has emerged out of its hidebound, white male, western-based past, with research from around the world and a full diversity of scientists. (One area where this manifests itself is how scientific names of dinosaurs have started to reflect a more encompassing and respectful view of where fossils originate.)

For anyone who pays attention to the natural world, birds are ubiquitous. I can’t remember a day without encountering one, no matter where I have been, from the urban chaos of downtown Tokyo to the Douglas firs of my backyard to alpine meadows high in the Cascades. As a geogeek, I have long known that birds are dinosaurs, but Brusatte’s book puts birds in a new and exciting perspective, linking these amazing animals to me, to the ecosystems I love, and deep into the planetary past when dinosaurs ruled the world. Now, they simply rule the sky but what a graceful reign it is. No matter where you look, the connective tissues of life abound, glorious in their complexity and beauty.

If you are interested, I’ll be chatting with Steve Brusatte about his new book on Saturday, April 25, at Town Hall at 7:30PM. Here’s how to register.

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