How Did Dinosaurs Become Birds?

vxjnqrflw17t9b6pfevz

Most paleontologists agree that birds are living dinosaurs, the distant evolutionary descendants of animals like Tyrannosaurus rex. Less clear, however is how dinosaurs evolved into the birds we know today.

Audubon is currently running a feature by Michael Balter about the enigmatic evolutionary history of modern birds, and the researchers working to solve its mysteries. Evolutionary biologist Ashley Heers, for example, studies the biomechanics of late-date birds to see if their movement at early stages of development bears any resemblance to that of their distant ancestors:

She is using the latest video and computer modeling technology to study how baby birds develop the ability to fly, looking for clues as to how dinosaurs evolved into birds—one of the most dramatic and successful evolutionary transformations in the history of life on earth.

“Every time I look at a bird, I am seeing a dinosaur,” she says. “That’s what makes it exciting for me

Archaeopteryx fossil

Archaeopteryx fossil

Heers came to England fresh from doing a Ph.D. with Kenneth Dial at the University of Montana’s Flight Laboratory in Missoula, Montana, probably the world’s leading research center on bird aeronautics. In the course of her research, she has piled up considerable evidence that baby birds do indeed resemble the avian dinosaur ancestors, which had feathers but little if any ability to fly. Thus at nine days old, her downy guinea fowl chicks have very small wings and shafts of primitive-looking feathers still pervious to the air. Their tufts are simple and symmetrical, lacking the complex structure of adult feathers, and the birds are too young to fly very far.

Heers takes one of the chicks out of the cardboard box and places it on an inclined pedestal about a foot away. The chick hesitates a second, then gathers up its wings, and its courage, and jumps back into the box. The video footage, captured on the computer, shows that while the chick relied mostly on its legs to make the leap, it also flapped its wings between two and three times, adding just enough lift to successfully bridge the gap. “They can’t yet fly very far,” Heers says, “but those tiny little wings are still very useful.” This strongly suggests, she adds, that even if early dinos evolved feathers for other reasons—to keep warm or for peacock-like sexual displays—they were already on their way to becoming birds.

Just how bird-like were dinosaurs? How dinosaur-like are modern birds? of modern birds, and the researchers and biomechanics researchers. She is using the latest video and computer modeling technology to study how baby birds develop the ability to fly, looking for clues as to how dinosaurs evolved into birds—one of the most dramatic and successful evolutionary transformations in the history of life on earth.

In her doctoral thesis, Heers drew comparisons between the developmental biology of modern day birds and the evolutionary stages of dinosaurs that, over millions of years, developed the capacity for powered flight. The observation was initially met with harsh criticism, but, over the last few years, Heers’s and Dials’s work has won them “respect and credibility, especially from leading paleontologists:

University of California-Berkeley researcher Kevin Padian, long a fan of Dial’s and Heers’s work, says the initial skepticism was totally off base: “This was exactly what was needed.”

[Stephen Brusatte, a paleontologist at the University of Edinburgh in the United Kingdom and a rising star in the paleontology world] adds, “Their work has been groundbreaking. They are studying living birds, and don’t just speculate based on fossils.” As for Heers, he says, “She’s brilliant. She’s not a traditional paleontologist but a real ornithologist.”

This is such a fun and compelling read. It’s as much an evolutionary backgrounder as it is a profile of interesting paleontologists, most of whom are basically rockstars, anyhow. Go read the rest of the Audubon piece for yourself.

Attribution: io9

 
 

Leave a Comment