But what if that arrowhead is more than 16,000 years old and the oldest record of human presence in North America?

That's what happened to a team of archaeological researchers at the Cooper's Ferry archeological site in Idaho . Their research was published Friday in Science Magazine, and it may have important scientific implications for studying human migration

The basic story of human habitation of North America, according to scientists, goes something like this: Giant glaciers melted in Canada, opening up an ice-free land bridge that humans used to first enter the continent from northern Asia. A beautiful story, really.

But that was roughly 14,800 years ago.

And the evidence this team found in Cooper's Ferry? Well, that's anywhere from 15,000 to 16,560 years old -- an entire millennium before that ice-free pathway.

The discovery basically means that early humans may not have populated North America via land. Instead, they most likely came through water, using a Pacific coastal route.

Loren Davis is the lead archaeologist on the dig. He told CNN the findings were significant.

"It begins to raise questions about these long-held ideas," he said. "Now we have a new set of facts to begin to make us question the things we thought we understood about the way things happened in the past."

What researchers found

Davis first went to Cooper's Ferry in 1997, after reading earlier studies that found spearheads and other tools in the 1960s, back when researchers didn't have the resources to date the artifacts.

Now, that's changed. 1997 was just a test excavation, and Davis returned with a team in 2009 to do some real digging, staying at the site until 2018.

The team basically uncovered a campsite, finding stone tools, the remains of a fire pit and broken up bones of medium to large animals, something like elk or deer.

It wasn't just a one-time stop, either. Davis said people returned to the site, and the team found newer artifacts closer to the surface and older ones further down. They dated the artifacts using radiocarbon dating, what Davis called the "gold standard" in aging things younger than 50,000 years. It's the most accurate dating method for archeologists, so the team is confident in their accuracy.

How did the humans get to Idaho?

Though Idaho is pretty far inland, blocked from the coast by Oregon, it's connected to the coast by the Columbia River. Cooper's Ferry lies near the Salmon River, a tributary of the Columbia River, Davis said. So it's not hard to see how these humans made their way to the area.

"[They] likely came down the Pacific coast, turned left and went inland when they encountered the mouth of the Columbia river," Davis told CNN. "There would have been ice on the left and ocean on the right. Columbia river would have been an off-ramp, so to speak, the easiest path to move into the interior of North America."

That doesn't mean that no one came down through the ice path, of course. It just means that people were already in North America when that happened.

Similar tools to what Davis found in Cooper's Ferry have also been found in northern Japan. Davis hypothesizes that that's where those early settlers came from.

But to verify, he'll have to do a little more digging.