Intelligence Evolved Twice: How Birds and Mammals Took Separate Paths to Genius
For millennia, people have seen intelligence as a singular evolutionary triumph, a pinnacle attained only by mammals, with primates (and finally, humans) at the top. But apparently nature had other ideas. Modern ground-breaking studies show that intelligence developed twice in two quite different spheres of life: mammals and birds, not once.
Birds have long surprised us from ravens solving difficult puzzles to parrots surpassing apes in memory tests. Still, their brains lack the neocortex, the six-layered neural structure long regarded as the center of mammalian intelligence. How then do they compare in cognitive ability to rival primates? The solution resides in an amazing case of convergent evolution whereby nature separately created two separate blueprints for genius. Using state-of- the-art genetic and neurobiological tools, recent studies have revealed that birds and mammals arrived at intelligence via quite different evolutionary paths, so redefining our knowledge of cognition itself.
The Bird Brain Myth: How Science Got It Wrong for Decades
Birds were viewed as natural-born animals with a little capacity to learn for the majority during the early 20th century. Their absence of a neurocortex meant that their brains were deemed ineffective at thinking. "Bird-brained," as a term "bird-brained" came to be employed as a synonym for stupidity due to outdated neuroanatomy.
The pivotal moment came in the early 1960s during the 1960s, when the neuroanatomist Harvey Karten found that birds have a brain structure called the dorsal ventral Ridge (DVR) and despite its messy appearance has very similar functions as the mammalian neocortex. According to the research of Karten it is possible that a similar neural structure passed down from a distant reptile ancestor may be shared by birds as well as mammals.
A few years later, however, the anatomist Luis Puelles, studying embryonic development, challenged this view. He concluded that the Avian DVR and mammalian neocortex grow from different areas of the brain that are growing, and that they evolved in a different way. This led to an argument that was heated over whether intelligence was created in two instances or was it part of a shared heritage?
The Rosetta Stone of Avian Intelligence: A Fossil That Rewrote History
The missing link of 2024 emerged from a well-preserved 80 million-year-old bird skull known as Navaornis Hestiae. The skull was found in Brazil the fossil revealed the brain's structure, which spans 70 million years of the evolution of avians, halfway between the early dinosaurs and modern birds.
Researchers rebuilt the brain of Navaornis with micro-CT scans. The results were remarkable: while its cerebrum, which is connected to cognition was higher-level than Archaeopteryx the earliest-known bird-like dinosaur, it did not have the intricate cerebellum that is found present in contemporary birds. This suggests that the bird's intelligence evolved in stages and was able to deal with issues before the development of sophisticated flight control.
The co-lead author of this research the study Dr. Guillermo Navalonthat "this fossil is the Rosetta Stone of avian intelligence." "It demonstrates that birds were already on a cognitive trajectory separate from mammals millions of years before humans even existed."
The Social and Ecological Drivers of Avian Genius
Why did intelligence in birds develop at all? Their social systems and ecology provide the key:
- Corvids and parrots lead dynamic groups in which alliances, rivalries, and dishonesty are common mirroring primate societies.
- Generalist foragers such as kea parrots must daily solve new food challenges, so fostering cognitive flexibility.
- Like humans, intelligent birds have long developmental times that let for brain expansion and learning.
Unmatched by most animals, Clark's nutcrackers have spatial memory allowing them to recall the sites of 2,500 seed stores over 150 square miles.
