In the last couple of decades increasing numbers of articles have made it to the popular press about the intelligence of birds, be it tool-making in Caledonian crows or the obituary for the talking, counting, African Grey Parrot, Alex, in The Economist magazine. This has helped to break a longstanding public conception that birds are stupid, based on their small “bird brains”.
What’s your EQ?
Animal scientists have since come to recognize that it is relative rather than absolute brain size which is a better arbiter of intelligence. Brain-to-body mass ratios, or “encephalization quotients”, reveal a startlingly different story about bird brains, as the following diagram shows:
The brain-to-body ratio of crows and parrots is more like primates than birds, leading corvid ethologists John Marzluff and Tony Angell to describe them as “flying monkeys”.
The ancient basis of bird and mammal intelligence
More recently it has been found that a huge proportion of songbird (passeriform) brains are taken up by a neocortex like structure called the neopallium. Now the independent evolution of neocortical intelligence in birds and mammals is about as improbable as the independent evolution of the eye in vertebrates, molluscs and arthropods, but the story is actually much more interesting than that: just as the different eyes of humans, octopuses and insects are now understood to have evolved from photo-receptive cells in a common ancestor 600 million years ago, the column-structure of the mammalian neocortex and the avian neopallium is likely to have been around some some 290 million years ago in a shared amniote ancestor that would have looked like a small newt or lizard. This proto-cortical brain structure provided an evolutionary platform waiting to be built upon by any reptile, dinosaur or mammalian descendent which found a need to do so, and it certainly did so in some of the avian dinosaurs we call birds.
We were fortunate, that any remnants of dinosaur sociality and intelligence survived in birds, but who knows what may have been lost? Other carnivorous bipedal dinosaurs may have also pair-bonded, shared incubation and feeding responsibilities while incubating eggs, raised their young for protracted periods, and even co-operatively hunted to bring down prey. There is some suggestive fossil evidence to suggest these possibilities. Who knows, some dinosaurs may have even enjoyed play?
The profligacy and wastefulness of evolution
When I was a child, I was fascinated by dinosaurs. The idea that for hundreds of millions of years the world was once populated by a totally different cast of creatures even more diverse and exotic than those alive today – millions of years before humans, primates or even mammals walked the earth.
The dazzling idea that had me in its spell (but I was too unsophisticated to grasp) was the profligacy and wastefulness of evolution. Naïve and especially theological readings of evolutionary history describe it is a relentless and inexorable ascent of complexity and diversity from simple single-celled organisms to self-aware human beings.
It is true that various accidents about Earth’s history and location make it one of those small pockets of the universe which swims against the general tide of entropy: life managed to take root here and convert the heat of the Earth’s magma or the light of the sun into chemical energy from which more and more elaborate organisms have successively been built.
But the march of evolution has not been one of inexorable progress. Earth’s history is littered with the countless corpses of creatures with startlingly adaptive mutations which came to an unlucky end before they could reproduce, and the great extinction events which ultimately paved the way for the success of mammals and the evolution of human beings often did so by setting back the diversity and sophistication of life on Earth by hundreds of millions of years.
There are corvid fossils 17 million years old and parrot fossils roughly 50 million years old. The true age of these birds might be even older, with many scientists arguing that the diversification of bird species chiefly took place before the great Cretaceous-Tertiary extinction 65 million years ago. With these birds rivalling apes in cognitive tests, it looks likely that birds and their dinosaur relatives have been outwitting our hominid and mammalian ancestors until extremely recently.
We will probably never know first hand what the extinct dinosaur relatives of modern birds were capable of. Fans of Jurassic park hoping to one-day encounter a live velociraptor or tyrannosaurus will be disappointed to hear that efforts to recover dinosaur DNA has met with repeated failure.
The paleontologist Jack Horner drily recounts his frustrated endeavours to build a dinosaur in the following TED talk, but while he may not be able to reconstruct a T-rex, he may be able to provide us with an interesting compromise: a reverse-engineered dinosaur from the modern chicken, or as he likes to call it, a “chickensaurus”: