Reflexive Behavior and the Lack of a Neocortex
Pecking disorder, or more accurately, a lack of it, has been a long-standing assumption about the cognitive abilities of birds. The creatures lack a neocortex, the complex outer layer of the brain responsible for language, communication, and reasoning. In the past, neuroanatomists believed that birds had simpler, less developed brain structures, which could only support reflexive behavior. “ For the longest time, it was thought that this is the center of cognition, and you need this kind of anatomy to develop advanced cognitive abilities,” said Bastienne Zaremba, a postdoctoral researcher studying the evolution of the brain at Heidelberg University.
A New Perspective: Harvey Karten’s Groundbreaking Work
However, in the 1960s, Harvey Karten, a young neuroanatomist at MIT, challenged this conventional thinking. He compared brain circuits in mammals and birds, including pigeons, owls, and chickens, and found surprising similarities between the two. The brain regions thought to be involved only in reflexive movements were built from neural circuits that resembled those found in the mammalian neocortex. In 1969, Karten wrote a paper that completely changed the discussion in the field. His work sparked a lot of interest in the bird brain and laid the foundation for future research.
A Debate Rages On
Despite Karten’s groundbreaking work, the debate over the evolution of the brain continued. Luis Puelles, an anatomist at the University of Murcia in Spain, proposed an alternative theory. By comparing embryos at different stages of development, he found that the mammalian neocortex and the avian dorsal ventricular ridge (DVR) developed from distinct areas of the embryo’s pallium, a brain region shared by all vertebrates. The debate between Karten and Puelles continued for decades. However, recent studies have shed new light on the evolution of the brain.
New Studies Challenge Conventional Wisdom
Two new studies, conducted by independent teams of researchers, used single-cell RNA sequencing to compare neuronal circuits in adult brains and embryonic development. These studies found that the mature circuits looked remarkably alike across animals, but were built differently. In one study, Fernando García-Moreno and his team tracked cells in the palliums of chickens, mice, and geckos at various embryonic stages. They found that the mature circuits were built with similar circuitry, but the neurons that composed those neural circuits were distinct. Another study, led by Maria Tosches and Bastienne Zaremba, created a comprehensive atlas of the bird pallium. By comparing the bird pallium to lizard and mouse palliums, they found that the neocortex and DVR were built with similar circuitry, but the neurons that composed those neural circuits were distinct.
Evolutionary Convergence
These studies provide the clearest evidence yet that birds and mammals independently evolved brain regions for complex cognition. They also echo previous research that found the mammalian neocortex evolved independently from the reptile DVR. However, the findings also suggest that there was some inheritance from a common ancestor. A third study found that mice, chickens, and humans share some stretches of DNA that influence the development of the neocortex or DVR, suggesting that similar genetic tools are at work in both types of animals.
Building Intelligence
Intelligence doesn’t come with an instruction manual, and it’s hard to define. Innovations can happen throughout an animal’s biology, whether in new genes and their regulation, or in new neuron types, circuits, and brain regions. The findings of these studies highlight the differences in neural solutions that various organisms have evolved to solve similar problems of living in a complex world and adapting to a rapidly changing environment.
Convergent Evolution
Convergent evolution is a phenomenon where similar innovations evolve independently in different species. This is seen across life, from the evolution of camera-like eyes in octopuses and squids to the development of complex social behavior in insects. The study of convergent evolution can provide insights into the evolution of intelligence. By understanding how different species have evolved to solve similar problems, we can gain a deeper understanding of the building blocks of a brain that can think critically, use tools, or form abstract ideas.
Implications for Artificial Intelligence
The study of bird intelligence can also provide insights into the development of artificial intelligence. By studying the neural structures and functions of birds, we can gain a better understanding of how to design more intelligent machines. For example, the way we currently think about using insights from evolution to improve AI is very anthropocentric. However, by studying the neural structures and functions of birds, we can develop a more bird-like perspective on intelligence. Bradley Colquitt, a molecular neuroscientist at the University of California, Santa Cruz, said, “It would be exciting to figure out how octopuses evolved intelligence using really divergent neural structures. That way, it might be possible to pinpoint any absolute constraints on evolving intelligence across all animal species, not just vertebrates.”
The study of bird intelligence can also provide insights into the search for extraterrestrial intelligence. By understanding the building blocks of a brain that can think critically, use tools, or form abstract ideas, we can develop a more comprehensive understanding of the universe. In conclusion, the study of bird intelligence has challenged conventional wisdom and provided new insights into the evolution of the brain. By studying the neural structures and functions of birds, we can gain a deeper understanding of the building blocks of a brain that can think critically, use tools, or form abstract ideas, and develop more intelligent machines.
