"There's absolutely no DNA evidence," Holliday said.
Archaeological evidence is also scarce. A few East Coast sites, such as Cactus Hill in Virginia and Meadowcroft Rockshelter in Pennsylvania, may have been inhabited up to 16,000 to 18,000 years ago, but the dating and provenance of artifacts from the sites are debatable, Holliday said.
Either way, it's impossible to know how the mastodon tusk and knife are connected, Holliday said.
"You would have to demonstrate that the artifact was associated with the mastodon - in the same geologic layers," Holliday said.
But many other fishing boats could have come and mixed up the sediments at the ocean floor prior to the scallop trawler's dredging. And with thousands of years of ocean currents, the artifacts could have originated in different locations. For all anybody knows, an ancient fisherman could have dropped the knife from a canoe 8,000 years ago, Holliday said.
The new discovery was described in May in a chapter of the book "Prehistoric Archaeology on the Continental Shelf" (Springer, 2014), though it has not been published in a peer-reviewed journal.