But the soil in most parts of New England is very acidic, compared to soils in some other places in the world. Anything organic like wood, leather, fiber, fur is rotted past recognition and recovery', often within about 300 years. Stone and carbon are not organic and they last in the ground almost indefinitely. Not any more. But then new laws were made.
Bone now is tested to see whether it's human and how old.
If it is Native American, it is returned to the Native American community for ceremonial reburial. M.A.S.'s Robbins Museum now has no human bone of any sort. Thank heavens, the early people in the Northeast U.S. had no gold, so none ever has been found in New England sites. If it's stone it may be an arrowhead, but it may or may not be from the old days. An archaeologist usually can tell by the way it is made, the rock it's made from, where it was found, and what else was near it.