When Yale University paleontologist Nicholas Longrich began studying a prehistoric bird called Archaeopteryx, he noticed something unexpected.
For starters, the bird had small feathers on its hind legs. When he began doing a feather-by-feather reconstruction of its wings, working from a fossil in Germany, he found it didn’t look like a modern bird at all. Instead of the single layer of feathers that give modern birds their dextrous flight abilities, the fossil appeared to have layers of feathers stacked on top of each other, almost like two-ply tissues.
“I realized you couldn’t really get from what the fossils showed to the way people were drawing it,” Longrich said. “People have been drawing the wing this one way for more than 100 years, and had this particular idea about what the wing would look like. And this is coming along after more than a century and saying we got it wrong.”
His painstaking study of the Archaeopteryx fossil suggested to Longrich that this Jurassic-era bird had a primitive wing, and may not have been very good at flying. But instead of publishing his observation, he decided to sit on it. He wasn’t sure that his colleagues would be convinced; it might have been something strange about the way the specimen he was studying was fossilized.
A few years later, a scientist working down the hall from him, Jakob Vinther, began studying a fossil of a feathered dinosaur that had been recently discovered in China, called Anchiornis huxleyi. Vinther was not a bird specialist—in fact, Longrich said, Vinther normally studied fossils of ancient squid, octopi, and worms. But that also meant Vinther didn’t have the same preconceptions, and when he looked at the fossil he also saw wings with multiple layers of feathers.
The scientists have now published their work, describing the primitive wings of both Archaeopteryx and Anchiornis, in the journal Current Biology. Longrich says that the wing probably functioned, but not as well as in modern birds. Archeaopteryx probably was “O.K. at getting around from point A to point B, level flight or flapping flight,” Longrich said, but not so good at flying at low speeds or hovering. The feathered dinosaur, on the other hand, was probably more of a glider, he said.
Arkhat Abzhanov, associate professor of organismic and evolutionary biology at Harvard University, said that the study sheds new light on both species and the evolution of wing design. It also, he says, raises a question about when modern birds’ wing structure evolved, and why there has been so little change since.
“Curiously, these dramatic early alterations in the wing structure were followed by a 130-million-year period of conservation which the authors likened to the rapid advances in early human aircraft engineering which was followed up by the current period of rather limited tinkering,” Abzhanov, who was not involved in the research, wrote in an e-mail.
The study also points to the importance in science of keeping an open mind and challenging prevailing assumptions.
Longrich noted that Archeaopteryx was discovered in the mid-1800s, not long after Charles Darwin wrote “On the Origin of Species.” For over a century, people pretty much assumed the wing of the archaic bird was just like a modern bird’s, with little reason to challenge that assumption. But as fossils have been discovered in China, he said, they’ve allowed scientists to look at old fossils in a new light. That highlights one of the truly difficult things about science: knowledge is necessary, but to stick too closely to longstanding explanations can be limiting.
“Interpreting these fossils is really complicated, and there’s this interplay between having an interpretation going into it that will help guide you to understand the specimen, but also ignorance or openminededness, like a child would have, where you’re just kind of seeing what’s there and interpreting what’s there,” Longrich said. “That kind of naïve interpretation and the ability to look at the fossils that way, even after you’ve seen a lot of them, is really important.”