Intelligence on Earth Evolved Independently at Least Twice

Summary

“How we end up with similar circuitry was more flexible than I would have expected,” Zaremba said. “You can build the same circuits from different cell types.”Zaremba and her team also found that in the bird pallium, neurons that start development in different regions can mature into the same type of neuron in the adult. This pushed against previous views, which held that distinct regions of the embryo must generate different types of neurons.There’s limited degrees of freedom into which you can generate an intelligent brain, at least within vertebrates.Maria Tosches, Columbia UniversityIn mammals, brain development follows an intuitive path: The cells in the embryo’s amygdala region at the start of development end up in the adult amygdala. The cells in the embryo’s cortex region end up in the adult cortex. But in birds, “there is a fantastic reorganization of the forebrain,” Güntürkün said, that is “nothing that we had expected.”Taken together, the studies provide the clearest evidence yet that birds and mammals independently evolved brain regions for complex cognition. They also echo previous research from Tosches’ lab, which found that the mammalian neocortex evolved independently from the reptile DVR.Still, it seems likely there was some inheritance from a common ancestor. In a third study that used deep learning, Kempynck and his coauthor Nikolai Hecker 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. And as previous studies had suggested, the research groups found that inhibitory neurons, or those that silence and modulate neural signals, were conserved across birds and mammals.The findings haven’t completely resolved Karten and Puelles’ debate, however. Whose ideas were closer to the truth? Tosches said that Puelles was right, while Güntürkün thought the findings better reflect Karten’s ideas, though would partly...