College of Science

Study on how birds evolved from dinosaurs could have human health implications


An unexpected discovery by scientists researching how modern-day birds evolved from their dinosaur ancestors could potentially impact how humans, especially children, are treated with corticosteroids and other anti-inflammatory medications.

Susan Chapman, an associate professor in the Clemson University Department of Biological Sciences, and collaborators compared the tails of chickens — considered by scientists to be modern avian dinosaurs — with that of Archaeopteryx, a small winged and feathered dinosaur with a long tail that lived at the end of the Jurassic period.

Archaeopteryx lived about 150 million years ago. The first short-tailed bird appeared in the fossil record about 130 million years ago.


This research started as part of paleontologist Jack Horner’s DinoChicken Project. Horner, who served as the technical adviser for the first five Jurassic Park films and was the inspiration for one of the lead characters, wanted to see if scientists could reverse-engineer ancestral traits of dinosaurs from modern birds.

Headshot of Susan Chapman, associate professor in the Clemson Department of Biological Sciences
Susan Chapman

“We’re trying to understand how you had a dinosaur turn into a bird, and one of the ways to understand how that happened is to try to turn a bird back into a dinosaur. We’re not trying to make little dinosaur dragons or anything like that. We’re trying to understand how animals can change and adapt to the environment,” Chapman said. “We’re looking at evolutionary transitions and how, trait by trait, dinosaurs evolved into modern birds.”

They found the main changes to birds’ tails resulted from fusion of the vertebrae. Some of the vertebrae were fused into the pelvis and others fused at the end of the tail, resulting in a shorter tail. The change is considered an adaptation for flight. 

“We were interested in how birds have these multiple regions of fusion in their spine, how that happened,” Chapman said.

Surprising cause

Surprisingly, they discovered inflammation caused the vertebrae to fuse.

“Inflammation doesn’t usually happen in development. We think about inflammation as a pathological response to injury or disease. For instance, if you break a bone and you need the two pieces of bone to mend back together, inflammation starts that process,” said Dana Rashid, an assistant research professor in the Montana State University Department of Microbiology and Cell Biology, who co-led the project. “When we found that inflammation causes the fusion of these vertebrae, we found the first demonstration of inflammation in normal bone development.”

To confirm their findings, the scientists compared tail development of healthy birds to those that had been treated with an anti-inflammatory drug. The anti-inflammatory drug inhibited the fusion without any DNA manipulation, Rashid said.

Susan Chapman (left) and colleague Dana Rashid (right) discovered inflammation caused vertebrae in bird tails to fuse. The discovery surprised scientists because inflammation is usually a pathological response to injury or disease.

Inflammatory diseases

The findings may help shed light on certain types of arthritis and other diseases such as ankylosing spondylitis, Chapman said.

Ankylosing spondylitis is an inflammatory disease that, over time, causes some vertebrae in the spine to fuse, making the spine less flexible. Symptoms typically begin in early adulthood.

Nearly 3 million Americans, or nearly one in every 100 people, have ankylosing spondylitis. 

Rashid said while scientists knew corticosteroids affects bones, none had looked at whether they inhibit bone fusion.

“There are lots of other bone fusion events as your skeleton matures. For all we know, it could be the same mechanism. We’re a little concerned about kids who take corticosteroids for asthma during the timeframe that their sacrum is fusing and other fusion events are happening. It’s possible that corticosteroids might have a more broad effect on skeletal maturation than we originally thought,” Rashid said. “So this project, that started out to re-engineer ancestral dinosaur traits in birds, has crossed over to human health.”

Details about the findings were published in the journal PNAS in an article titled “Nonpathological inflammation drives the development of an avian flight adaptation.”

Other scientists involved in the research were Joseph Sheheen, Tori Huey and Jackson Sanders from Clemson; Kevin Surya and Jovanka Voyich from Montana State University and Horner, who is at Chapman University. 

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