Scientists at the University of Michigan have uncovered something remarkable about the evolution of songbirds — and they did it with the help of artificial intelligence and more than 15,000 museum skeletons.
Evolution doesn’t move at a steady pace
The study, published in Nature Ecology & Evolution, focused on Passeriformes — the vast bird order that includes most of the world’s songbirds. Using AI, the researchers analyzed skeletal measurements from over 2,000 species and found that these birds didn’t evolve gradually and continuously. Instead, they changed in sudden, dramatic bursts — and those bursts lined up, strikingly, with major shifts in Earth’s climate.
“There’s a long history, going back 100 years, that predicts the emergence of new groups is often associated with an explosive burst of diversification,” said lead author Jake Berv. “That’s what theory predicts, and that seems to be what we see in the data as well.”
A machine that reads bones
Collecting data at this scale required a tool that didn’t exist until recently. The team used Skelevision — an AI system developed at the University of Michigan in collaboration with New York University — which photographs bird skeletons against a measurement grid and automatically records the dimensions of 12 bones per specimen.
Each skeleton takes about 45 seconds to scan. Over the course of the project, the system processed more than 15,000 specimens, most from the University of Michigan Museum of Zoology, generating over 170,000 individual measurements.
45 million years, reconstructed
To make sense of all that data, lead author Jake Berv developed a new statistical method called bifrost, which analyses a bird’s skeleton as a whole rather than bone by bone. The approach allowed the team to trace how passerine body shapes shifted across roughly 45 million years of evolution.
The results were striking. One of the most intense periods of evolutionary change occurred around 35 million years ago — coinciding with the Eocene-Oligocene transition, a period of dramatic global cooling. A cluster of slowdowns appeared around 15 million years ago, lining up with another major geological event.
“This pattern of rare, big increases in the rates of evolution and lots of small decreases is really consistent with lineages exploring new ecological space and changing rapidly to take advantage of that opportunity,” said senior author Brian Weeks.
Where you live shapes how fast you evolve
The team also found that geography plays a role. Bird communities at higher latitudes — where seasonal temperature swings are more extreme — tend to evolve faster than those near the equator. The same pressure that drives rapid change across millions of years appears to be visible in the geographic patterns of species alive today.
Museums, reimagined
The study is also a testament to something easy to overlook: the scientific value of natural history museum collections. Specimens gathered by collectors over centuries are now being read by computers in ways their original owners could never have imagined.
“It’s fun to imagine what early collectors would make of how we’re using the specimens they collected,” Weeks said. “I imagine it would blow their minds.”
A window into our own moment
The researchers believe their findings could offer clues about how species might respond to the rapid climate change happening right now.
“To have a chance of understanding the long-term impact of human activity on Earth, we have to study the relationship between events in Earth’s history and evolutionary transitions,” Berv said.
Songbirds have been navigating a changing planet for 45 million years. Understanding how they did it may help us understand what comes next.