The Cretaceous–Tertiary mass extinction 65 million years ago may have wiped out the dinosaurs, but those that survived – the ancestors of today’s birds – may have done so because of their bird brains.
Analysis of computer tomography (CT) scans of fossilised bird skulls shows they had a more developed, larger brain than previously thought.
‘Birds today are the direct descendents of the Cretaceous extinction survivors, and they went on to become one of the most successful and diverse groups on the planet,’ says Natural History Museum palaeontologist (fossil expert), Dr Stig Walsh.
‘There were other flying animals around, such as pterosaurs and older groups of birds,’ says Dr Walsh, ‘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.’
A larger and more complex brain may have given them a competitive advantage over the other more ancient birds and pterosaurs, helping them to better adapt when the environment changed after the mass extinction event.
Larger brains in living birds
Species of living birds that have larger brains are more likely to live in more socially complex groups and exhibit more complex and flexible behaviour than those with smaller brains.
For instance, members of the crow family have large brains, and some make and use tools, inventing cunning ways to find food.
Previous research has suggested birds with larger brains are more likely to survive if introduced to new environments than those with smaller brains.
These results suggest that this kind of behavioural flexibility was already a characteristic of the ancestors of modern birds before the Cretaceous–Tertiary extinction event.
Surviving the aftermath
‘In the aftermath of the extinction event, life must have been especially challenging,’ says Dr Walsh.
‘Birds that were not able to adapt to rapidly changing environments and food availability did not survive, whereas the flexible behaviour of the large-brained individuals would have allowed them to think their way around the problem.’
I'm not sure I buy this one.