The discovery of an ancient bear bone in a County Clare cave has pushed back the date of human existence in Ireland by 2,500 years and altered the history of human colonization of the island. The bone has been stored at the National Museum of Ireland for almost 100 years ago, and now a new study has used radiocarbon dating to reveal a new chapter of Irish history.

Prior to the finding, the oldest evidence of human activity on Ireland was 8,000 B.C. during the Mesolithic period. This evidence suggests that humans had been present on the island for around 10,000 years.

The new finding of the bear patella, or knee bone, suggests that humans existed in Ireland at 10,500 B.C., around 12,500 years ago. The finding is a huge breakthrough for archaeologists and solidifies the existence of humans on Ireland during the Paleolithic period.

"Archaeologists have been searching for the Irish Paleolithic since the 19th century, and now, finally, the first piece of the jigsaw has been revealed. This find adds a new chapter to the human history of Ireland," said Marion Dowd, co-author of the study.

After first examining the fossil using radiocarbon dating, Dowd was surprised at the Paleolithic date.

"When a Paleolithic date was returned, it came as quite a shock," she said. "Here we had evidence of someone butchering a brown bear carcass and cutting through the knee probably to extract the tendons. Yes, we expected a prehistoric date, but the Paleolithic result took us completely by surprise."

In order to confirm the validity of the findings, Dowd sent the fossil to a team of bone experts who were unaware of the radiocarbon dating results. Still, they found that the cut marks were made on fresh bone, confirming that they were present at the same date as the bone and thus supporting the finding that it originated from the Paleolithic period.

"This made sense as the location of the marks spoke of someone trying to cut through the tough knee joint, perhaps someone who was inexperienced," Dowd said. "In their repeated attempts, they left seven marks on the bone surface. The implement used would probably have been something like a long flint blade."

She added: "The bone was in fresh condition meaning that people were carrying out activities in the immediate vicinity - possibly butchering a bear inside the cave or at the cave entrance."

The team hopes that the findings will stimulate new research into the colonization of Ireland with a focus on the "human" side of things.

"From a zoological point of view, this is very exciting, since up to now we have not factored in a possible 'human-dimension' when we are studying patterns of colonization and local extinctions of species to Ireland," said Ruth Carden, co-author of the research along with Dowd.

The findings were published in the March 21 issue of Quaternary Science Reviews.