Despite having radically different brain structures from mammals, some birds display cognitive abilities rivaling those of great apes. Now, researchers at Heidelberg University have mapped how these remarkable capabilities evolved, challenging long-held assumptions about brain development and revealing unexpected similarities between bird and mammal minds.
The groundbreaking study, published in Science, uses cutting-edge single-cell technology to examine the pallium – the brain region responsible for learning, memory, and complex thinking in both birds and mammals. While human brains feature a folded cerebral cortex, bird brains evolved a completely different architecture to achieve similar cognitive feats.
“Our findings challenge previous theories that proposed a simple one-to-one correspondence between brain regions in birds and mammals based on their location,” explains Dr. Bastienne Zaremba of Heidelberg University’s Center for Molecular Biology, who participated in the research.
The research team, led by Professor Henrik Kaessmann, created detailed maps of cell types in the chicken brain and compared them with similar data from mice and reptiles. Their analysis revealed a complex evolutionary mosaic, where some neural circuits remained virtually unchanged for hundreds of millions of years while others underwent dramatic transformations.
Perhaps most surprisingly, the researchers discovered that neurons in the bird mesopallium share unexpected similarities with neurons in the deep layers of the mammalian neocortex – the brain region responsible for higher cognitive functions. This finding challenges existing theories about how these brain regions evolved.
The study also sheds new light on the hyperpallium, a unique brain structure found only in birds. While scientists previously thought this region corresponded directly to the mammalian neocortex, the new research reveals a more nuanced picture. Some neurons show similarities, but others are fundamentally different.
Another intriguing discovery concerns neurons in two distant regions of the bird brain that show remarkable similarities despite originating from different areas during embryonic development. “We need to rethink the idea that a neuron’s final role is strictly determined by where it forms in the embryonic brain,” says Professor Kaessmann.
The research provides crucial insights into how nature can achieve similar cognitive outcomes through different evolutionary paths. While inhibitory neurons – cells that regulate brain activity – remained remarkably similar across species, excitatory neurons that transmit signals followed more diverse evolutionary trajectories.
Some brain regions, like the hippocampus which handles learning and memory, maintained strong similarities across species. However, other areas underwent dramatic reorganization while preserving their functional capabilities.
“To gain a differentiated understanding of brain evolution and the development of complex cognitive abilities in birds and mammals, molecular data that takes developmental processes into account is crucial,” adds Kaessmann.
The research, conducted in collaboration with Dr. Fernando García-Moreno of the University of the Basque Country and researchers from Sweden, was supported by the European Research Council, the government of the Autonomous Community of the Basque Country, and the Swedish Research Council.
These findings open new avenues for understanding how intelligence evolves and suggest that nature may have more ways of building sophisticated brains than previously thought. For scientists studying animal cognition and brain development, this research provides a new framework for understanding how different species can achieve similar mental capabilities through distinct evolutionary paths.