SYDNEY: The ancestors of modern birds may have survived the mass extinction that wiped out the rest of the dinosaurs because of their highly developed brains, a new study shows.
Computed tomography (CT) scans of the 55-million-year-old fossil skulls of two seabirds suggests that prehistoric birds had larger, more developed brains than we thought, say experts from the Natural History Museum in London, England.
“Birds today are the direct descendants of the Cretaceous extinction survivors, and went on to become one of the most successful and diverse groups on the planet,” said palaeontologist and study co-author Stig Walsh.
Until now scientists have had little evidence to explain why the ancestors of modern birds might have survived the Cretaceous-Tertiary (K-T) mass extinction event – caused by the impact of an asteroid or comet 65 million years ago – when all other groups of dinosaurs did not.
Other flying animals around at the time, including pterosaurs and some groups of birds did go extinct, so it wasn’t wings, feathers or warm-bloodedness that gave modern birds an edge, said study lead author Angela Milner. “It had to be something else, and it seems to be this bigger brain.”
The scientists believe that a larger, more complex brain could have given these birds a distinct competitive advantage, helping some to adapt to the totally different environments after the impact event.
Experts already knew that modern birds with large brains are able to live in more complex social groups and are better able to adapt behaviour than birds with small brains. For example, large-brained members of the crow family are known to make and use tools, using intuitive techniques to forage for food.
The new study, reported last month in the Zoological Journal of the Linnaean Society, included an analysis of the braincases of two fossil skulls from the Natural History Museum’s collection, which were dug up on England’s Isle of Sheppey.
Odontopteryx toliapica was a huge, gliding seabird with ‘bony teeth’ and a wingspan of six metres, and Prophaethon shrubsolei was an extinct tern-like tropical seabird. Using micro-CT scans, the team created virtual casts of the brain cavities to analyse the size and shape of the fossil brains.
The analysis revealed that the ancient brains were surprisingly similar to those of living birds today.
The 55-million-year-old skulls showed similar developments to modern birds in the part of the brain called the ‘wulst’, which controls sight, flight and the ability to learn and remember. This hints that after the cataclysm that sent many other species extinct, these birds were “better equipped to deal with challenging physical conditions,” said Milner.
John Long, a palaeontologist at the Museum of Victoria in Melbourne, Australia, said the research reveals “that bird brains underwent a rapid evolution from the brains of dinosaurs, and then became more or less fixed in overall shape and form once the specialised neurosensory functions for flight were developed.”
Long, who was not part of the team behind the research, added that this significant study highlights the real value of museum collections and shows how “cutting-edge technology is now revealing the hidden secrets of fossils we have had lying around in museums for many years.”