January 21, 2009

‘Birdbrains’ Helped Birds Survive Mass Extinction

According to researchers, brainpower may have enabled birds to survive in the midst of mass extinction.

Dinosaurs were wiped out during the Cretaceous-Tertiary mass extinction 65 million years ago, but birds were able to survive and thrive.

Recent analysis of fossil skulls using computer tomography scans shows that modern birds were able to survive the dire conditions due to their well-developed brains.

The birds' ability to solve problems gave them a crucial edge.

"Birdbrained is a dreadful misnomer," said Dr Angela Milner, of the Natural History Museum in London In an interview with the Times Online. "It's really quite an insult to birds when you think how sophisticated a lot of modern birds are.

"They can learn to talk, they can migrate over long distances, they have all sorts of capabilities and it all has to be crammed into a brain light enough that it doesn't stop them flying. They were in some ways more advanced than dinosaurs."

Milner, along with Dr. Stig Walsh, carried out the skull scans to see the shape and volume of the birds' brains.  The results led the researchers to believe that birds had advanced mental agility which allowed them to adapt to difficult situations. 

The researchers believe the key feature may have been the development of the wulst, a structure in the brain linked to visual awareness.

The wulst was small in birds alive after the mass extinction, but today the brain structure is much larger, especially in species that rely heavily on eyesight, such as owls. 

The structure was absent from creatures such as pterosaurs, ancient flying creatures, and earlier forms of birds that are now extinct.

Researchers believe today's birds are descendants of the avian species that survived the mass extinction believed to have been caused by a meteor that wiped out 85 percent of animal species.

"Our research suggests that the evolution of an expanded and structurally complex brain in the ancestors of living birds may have provided them with a competitive advantage over the more archaic bird lineages and pterosaurs," Dr. Walsh told Times Online.

"There were other flying animals around, such as pterosaurs and older groups of birds, but we've not really known why the ancestors of the birds we see today survived the extinction event and the others did not. It has been a great puzzle for us "“ until now."

Milner and Walsh compared the brain cavity of the earliest known bird, the Archaeopteryx, which dates back 147 million years, with two marine birds living after the mass extinction.

"Scans revealed the creatures' brain power because the shape of the brain is imprinted in the inside of the skull showing the shape and volume," said Dr. Walsh.

The modern birds, Odontopteryx toliapica and Prophaethon shrubsolei, dated back 55 million years and were related to today's pelicans, and albatrosses.

The researchers needed to use species that lived 10 million years after the extinction due to the fact that intact bird skulls are very rare.  The two marine species had very developed brains, too developed to have evolved after the extinction according to the scientists.

The researchers concluded that the modern-style birds living during the time of the extinction had to have brains comparable to birds alive today, both in their ability to control flight and sight, and in their ability to learn.

"In the aftermath of the extinction event, life must have been especially challenging. Birds that were not able to adapt to rapidly changing environments and food availability did not survive, whereas the flexible behavior of the large-brained individuals would have allowed them to think their way around the problem," Dr. Walsh said.

The study appears in the Zoological Journal of the Linnean Society.


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