Saw this article today:Ancient Bones Found In Detroit SuburbIt said the bones could have originated many years ago - 2000 to be exact.  I would be interested to know which civilization would have been through or living in that area that long ago.   

Perhaps some of the tribes who crossed the Land Bridge over the Bering Sea settled there.  Probably the same who advanced down the Mississippi River and formed the Mississippian Culture.  But I'd only be guessing.