Something in the back of my mind plus a little research made me suspect the purported age of this skull
may not have been accurate. So I wrote to the Minnesota Historical Society providing them with photos.
Two days later I received this reply from the head of Archaeology.
Still not bad news after all. And I just sold the skull to a school teacher who will continue to use it in education. Only now she can teach about this magnificent beast using real and accurate information.
“Thanks for sending the photos of the bison skull in your possession. Based on these images, this does appear to be a specimen of Bison bison, the modern form of American bison, and not one of the larger extinct varieties.
Estimating the age of this skull really isn't possible without some information about the context in which it was found. Finds of bison bone are relatively common in Minnesota, and modern bison have been present in the state from at least 6000 years ago until the mid-19th century. This specimen could potentially date to any time in that range.
The Historical Society does not collect natural history specimens; that is, animal bone or similar items that have no verifiable connection to human activity. Unless this bison skull was found in a context that indicates that it was, for instance, hunted and killed by humans, and you had evidence in hand to document that, this is not something that would be suitable for our collections.
The Science Museum has a substantial collection of large mammal specimens. You might check with them to see if they are interested in this skull. But, again, without information about the context in which it was found, the research value is very limited.
Thanks for your inquiry.
Head of ArchaeologyMinnesota Historical Society”