DEC 08, 2016 2:40 PM PST

Cancer is at Least 255-Million-Years-Old, New Study Finds

A graduate student interested in how teeth formed in an ancient fossil inadvertently uncovered what researchers are calling the oldest tumor of its kind to date. The discovery suggests cancer is older than even dinosaurs.

Small cluster of circles indicate where the tumor developed | Image: Whitney et al. 2016The fossil is a 255-year-old jaw bone of a gorgonopsian - an extinct animal that lived before mammals. Importantly, gorgonopsians were part of a group known as synapsids, which may be considered our mammal-like reptile ancestors. "Most synapsids are extinct, and we — that is, mammals — are their only living descendants," Whitney said. "To understand when and how our mammalian features evolved, we have to study fossils of synapsids, like the gorgonopsians."

While it was unearthed in 2007, researchers at the University of Washington did not know about the existence of a tumor in their fossil. It wasn’t until Megan Whitney came along and asked the question of how the teeth were nestled in the jaw bones that the team took a closer look at their specimen.

To answer her research questions, Whitney studied slices of the fossilized jaw. Under the microscope, she identified the unmistakable telltale signs of cancer. These were seen as tiny round clusters of miniature ‘toothlets’ at the root of the actual functioning canine tooth. The toothlets seem to have their own layers of dentin and enamel. "this gorgonopsian had what looks like a textbook compound odontoma," Whitney said in a statement.

"We think this is, by far, the oldest known instance of a compound odontoma," said Christian Sidor, the study’s senior author.

In humans an odontoma is a benign tumor linked to teeth development. Formally, odontomas are “miniature teeth that can cause resorption of the functional tooth root.” But while benign, the toothlets that arise can cause swelling and gum pain.

The discovery of the 255-year-old odontoma marks two remarkable milestones. First is that this sample would date cancer to pre-mammalian evolutionary history. In other words, cancer is older than we’ve ever imagined. Second, this type of cancer has not been seen in a non-mammalian animal before. “Odontomas have been reported in a handful of fossil mammals up to a few million years old but were previously unknown in deep pre-mammalian evolutionary history,” the authors wrote. This discovery completely shifts what we know about how cancer has evolved over millions of years in vertebrates.

To learn about the oldest cancer found in a closer relative to humans, check out the video below.

Additional sources: Live Science
About the Author
Doctorate (PhD)
I am a human geneticist, passionate about telling stories to make science more engaging and approachable. Find more of my writing at the Hopkins BioMedical Odyssey blog and at
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