Read more: Living dinosaurs: How birds took over the world
An asteroid strike killed off the dinosaurs and most of their relatives. Perhaps being birdbrained isn鈥檛 such a bad thing after all
The late Cretaceous may have been a-flutter with birds and bird-like dinosaurs, but for some reason only modern birds made it through the asteroid strike that triggered a mass extinction 65 million years ago. Every other type of dinosaur went extinct. Why they alone survived is one of the most vexing questions in the history of life.
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鈥淭he late Cretaceous was a-flutter with birds and dino-birds, but only one group survived鈥�
鈥淏eing small has advantages 鈥� you have more offspring, a shorter reproductive cycle and faster regeneration times. These things are very important in harsh conditions,鈥� says Xu. Being able to fly away from post-impact devastation must also have helped. Another plus point is warm-bloodedness, as regulating your body temperature means you can live in a wider range of environments. Yet this can鈥檛 be the whole story; plenty of archaic birds, dinosaurs and flying reptiles had similar attributes, but they were all scythed down.
Scans of the skulls of 55-million-year-old birds may provide part of the answer. These show that, like all living birds, they had an extremely dense area of brain tissue known as the wulst. This structure allows birds to get brainier without carrying much extra weight 鈥� the smarter the bird, the larger the wulst. 鈥淭he advent of the wulst seems to go hand in hand with the evolution of modern birds. It is tempting to speculate that this brain area is what made modern birds so adaptable and allowed them to become so successful,鈥� says Milner ().
Unfortunately we don鈥檛 know for sure whether Cretaceous neornithines had a wulst because the only confirmed fossil we have, Vegavis, lacks a skull.
Far from being a handicap, being bird-brained may have made the difference between life and death. Modern birds diversified quickly after the extinction. The second age of dinosaurs had begun.
