Birds are demonstrably a type of dinosaur. Yet they managed to survive the catastrophe 66 million years ago when an asteroid collided with Earth and wiped out all other dinosaurs. How was that possible? The question has long been unanswered, but a new study suggests that the birds’ brains were their salvation.
In the study, published in Science Advances, researchers at the University of Texas and the American Museum of Natural History in New York examined the nearly complete skull of a primitive bird that lived 70 million years ago, at the end of the age of the dinosaurs.
The bird, belonging to the genus Ichthyornis, was in some ways more like a typical dinosaur than a modern bird – not so strange considering that the birds are descended in a straight descending line from small predatory dinosaurs.
Larger brain
Among other things, Ichthyornis’ brain was quite small. The cerebral cortex, the region of the brain that controls the higher thought functions, such as memory and learning, is much larger in modern birds than in Ichtyornis.
Ichthyornis and its primitive relatives did not survive the collision with the asteroid, as did the ancestors of the birds we see around us today. The latter had probably in all cases developed a larger brain – and perhaps they survived the disaster thanks to their cognitive ability.
“Chicken Brain”
Admittedly, birds have not had a reputation for being particularly intelligent. People with limited thinking ability sometimes get the epithet “chicken brain”, or “birdbrain” as the English say.
But this is completely wrong. Birds have small brains but their brain cells are more densely packed than mammals and many groups, especially crows and parrots, actually have more brain cells than most mammals.
With the transition from Ichthyornis to modern birds, the shape of the brain changed dramatically, including a sharp growth of the entire cerebrum and a marked enlargement of the optical lobes where the visual sense is located. Evolution is not foresighted, but perhaps their future was secured there.
Flying dinosaurs
The birds (Aves) originated about 150 million years ago, at the end of the Jurassic period. The oldest known species, Archeopteryx lithografica, was about the size of a modern crow, had feathers and could probably fly, but was otherwise confusingly similar to a small predatory dinosaur. The similarity shows that the birds most likely originate directly from the predatory dinosaurs (Theropoda).
In the following millions of years, many different groups of primitive birds evolved, none of which survived the catastrophe 66 million years ago. Only one group survived, the ancestors of modern birds, possibly thanks to their large brains.
Source: Science Advances / TT
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