Bird brains: Fossil reveals roots of avian intelligence

A recent fossil discovery may revolutionize our understanding of bird brain evolution, shedding light on how the intelligence of modern birds developed. 

Researchers from the University of Cambridge and the Natural History Museum of Los Angeles County have identified a remarkably well-preserved bird fossil from the Mesozoic Era, approximately 80 million years old, named Navaornis hestiae. 

This ancient bird’s complete skull, roughly the size of a starling’s, was found in Brazil and offers a rare and detailed glimpse into the brains of early avian species.

Timeline of bird brain evolution

Scientists believe that Navaornis hestiae could serve as a kind of “Rosetta Stone” for understanding avian brain evolution. 

The fossilized skull bridges a 70-million-year gap in the evolutionary timeline between the 150-million-year-old Archaeopteryx, one of the earliest bird-like dinosaurs, and today’s birds. 

Its well-preserved structure has enabled researchers to digitally reconstruct the brain and understand the evolutionary steps leading to the unique cognitive abilities of modern birds.

“The brain structure of Navaornis is almost exactly intermediate between Archaeopteryx and modern birds,” said co-lead author Guillermo Navalón from Cambridge’s Department of Earth Sciences. “It was one of these moments in which the missing piece fits absolutely perfectly.” 

The skull’s preservation allowed for advanced micro-CT scanning, revealing a brain structure that suggests it had a larger cerebrum than Archaeopteryx, hinting at advanced cognitive functions not yet seen in other ancient bird-like dinosaurs.

Insights into cognitive evolution

While Navaornis was equipped with a more developed cerebrum, its cerebellum – a critical area for flight control in modern birds – was less evolved, indicating that its flight capabilities may have been simpler. 

“Modern birds have some of the most advanced cognitive capabilities in the animal kingdom, comparable only with mammals,” said senior author Daniel Field, a paleontologist at Cambridge. 

But understanding how and when these traits evolved has been elusive until now. 

The fossil offers direct insight into an important transitional phase for bird cognition, suggesting that Navaornis might have been capable of complex behaviors like finding food, shelter, or even engaging in elaborate social interactions.

Abilities of “opposite birds”

Though Navaornis has some similarities to modern birds, it belongs to a group called enantiornithines, or “opposite birds,” which diverged from modern avians more than 130 million years ago. 

Enantiornithines had developed feathers and could likely fly, but they lacked some of the brain features essential for the precise flight control seen in living birds. 

“This discovery shows that some of the birds flying over the heads of dinosaurs already had a fully modern skull geometry more than 80 million years ago,” said lead author Luis Chiappe from the Natural History Museum of Los Angeles County.  

But the brain anatomy of Navaornis raises new questions about how opposite birds achieved flight without the advanced cerebellar structures seen in contemporary birds.

A perfectly preserved fossil

Navaornis was discovered by William Nava, director of the Museum of Paleontology in Marília, Brazil, at a site that tens of millions of years ago likely consisted of slow-moving creeks, creating the ideal conditions for fossil preservation. 

This discovery marks the fourth major Mesozoic bird fossil identified by Field’s team, following Ichthyornis, Asteriornis (also called the “Wonderchicken”), and Janavis. 

Each of these fossils has been pivotal in helping to reconstruct the evolutionary path of birds, the most diverse group of living vertebrate animals.

Navalón, who co-led the study, expressed awe at the specimen’s remarkable state: “This fossil is truly so one-of-a-kind that I was awestruck from the moment I first saw it to the moment I finished assembling all the skull bones and the brain.” 

The research team hopes that this fossil’s exceptional quality is just the beginning; additional findings at this Brazilian site could yield even more insights into avian evolution.

Advancing our understanding of bird cognition

“This might be just one fossil, but it’s a key piece in the puzzle of bird brain evolution,” Field said. 

With the findings on Navaornis, researchers now have a clearer picture of the evolutionary transitions that led from early bird-like dinosaurs to today’s intelligent avian species, such as crows and parrots. 

Still, the discovery is just a first step. Future studies will focus on understanding Navaornis’s behavior and interaction with its environment, aiming to answer broader questions about how bird cognition has developed over time.

An early era in bird evolution

The team’s ongoing research on Mesozoic bird fossils combined with advanced imaging techniques is providing an unprecedented view of the evolutionary leaps in bird anatomy and cognition. 

The next steps include investigating how Navaornis and its contemporaries adapted to their surroundings and exploring whether their evolving brain structures offered an advantage in survival and social behavior.

This discovery stands as a significant milestone in the field, offering a unique window into an era when birds were just beginning to develop the traits that would eventually make them some of the most cognitively advanced animals on Earth. 

With continued research, Navaornis hestiae may reveal even more about the mysteries of bird brain evolution, helping scientists piece together the fascinating journey from ancient feathered dinosaurs to the vibrant bird species we see today.

The study is published in the journal Nature.

Image Credit: Júlia d’Oliveira

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