Brainy Birds Out-Thought Doomed Dinosaurs?

James Owen
for National Geographic News

February 2, 2009

Birds survived the global catastrophe that wiped out their dinosaur relatives due to superior brainpower, a new study suggests.

The idea came from examining a pair of prehistoric seabirds found in southeast England by Victorian-era fossil hunters, according to researchers from the Natural History Museum in London.

The two 55-million-year-old skulls suggest the ancestors of modern birds developed larger, more complex brains earlier than previously thought.

This implies that bird ancestors had a mental edge over non-birdlike dinos and flying reptiles, so they were better able to adapt after the so-called K-T mass extinction event around 65 million years ago, said study co-author Angela Milner.

Some ancient groups of birds did go extinct, she noted, so it wasn't feathers or warm-bloodedness that gave modern birds a leg up.

"It had to be something else, " she said, "and it seems to be this bigger brain."

Big Bird Brains

The study, published last month in the Zoological Journal of the Linnean Society, was based on two specimens from the Natural History Museum's vast fossil collection.

Odontopteryx toliapica belonged to an extinct group of giant, bony-toothed seabirds, while Prophaethon shrubsolei was a prehistoric relative of tern-like tropical seabirds.

Milner and colleagues used CT scans of the skulls to make models of the size and shape of the fossil birds' brains.

(Related: "T. Rex, Other Dinosaurs Had Heads Full of Air" [December 12, 2008].)

What they found is that the ancient bird brains were almost the same size as those in birds alive today. The older noggins also showed early growth of a brain region known as the wulst.

"It seems to be the area that's involved in more complex behavior and cognition, such as being able to learn about your environment and remember it," Milner said.

So after the K-T event, she said, these birds "were just better equipped to deal with challenging physical conditions."

Fossil bird skulls that have not been flattened out over time are extremely rare, and no examples are known from the time of the K-T event.

But Milner says the brain advances seen in the 55 million-year-old birds would probably have begun more than 65 million years ago.

And fossils of the oldest known bird, Archaeopteryx, which lived 147 million years ago, reveal its brain was "nowhere near as well developed as the ones we looked at," she said.

Desperately Seeking Fossils

Julia Clarke, a geoscientist at the University of Texas at Austin who was not involved with the study, says there are various competing theories to explain why birds outlived the dinosaurs.

One idea is that the ancestors of all living birds came from the southernmost part of the southern supercontinent Gondwana, where they escaped the worst of the environmental fallout from the K-T event.

Another theory is that modern bird lines evolved in coastal habitats that also were less heavily impacted.

As well as providing valuable new evidence for the evolution of birds, she said, the latest study offers an intriguing new theory that will motivate paleontologists to look harder and farther to find more fossils.

"We still desperately need good fossils sampling brain and skeletal features in the species that are very close but outside the [evolutionary tree] of all living birds," Clarke said.

"We can only get so close to understanding the brains of the earliest birds with the sample of known species currently available."