THURSDAY, Dec. 8, 2016 (HealthDay News) -- A fossil of a distant ancestor of today's mammals -- which include humans -- shows evidence of a benign tumor of the jaw, scientists report.
The finding pushes back by hundreds of millions of years the advent of these "toothlet" tumors, called odontomas, says a team from the University of Washington in Seattle.
The researchers discovered the compound odontoma tumor in the fossilized jaw of a gorgonopsian, a precursor to mammals that lived 255 million years ago. The fossil was unearthed in Tanzania in 2007.
Previously, the earliest known evidence of odontomas was in fossils of creatures living less than 1 million years ago.
According to the research team, gorgonopsian were distant mammal relatives and the top predators in the pre-dinosaur Permian era when they existed. These animals ranged in size from 2 feet to 10 feet in length, and were known as the "saber tooths of the Permian" because of their large canine teeth.
The Seattle team spotted the tumor -- a compound odontoma -- when looking at a fossilized gorgonopsian jaw. This benign tumor consists of small "toothlets" and tooth tissues like dentin and enamel. It grows within the gums or other soft tissues of the jaw and can cause pain and swelling, as well as disrupt the position of teeth and other tissues.
These benign tumors do not spread through the body, but are often removed because of the trouble they can cause.
"We think this is by far the oldest known instance of a compound odontoma," study senior author Christian Sidor, curator of vertebrate paleontology at the Burke Museum of Natural History and Culture, said in a university news release. "It would indicate that this is an ancient type of tumor."
"This discovery demonstrates how the fossil record can tell us a lot about our present-day lives -- even the diseases or pathologies that are part of our mammalian heritage," Sidor said.
The gorgonopsian tumor is not the oldest cancer ever recorded, however. According to the scientists, definite evidence of a tumor was seen in the fossil of a 300 million-year-old fish, and a possible case was seen in an even older fish fossil, dated to 350 million years ago.
The new findings are reported Dec. 8 in the journal JAMA Oncology.
Find out more about the history of cancer at the American Cancer Society.