Second hypothesis they would advance would be "old bone used in much late manufacture"; their third hypothesis would be claims of outright fraud.
In all three scenarios, the result would be the same: bury it in an unmarked box in a dark corner of a university museum's subbasement "to await further curating".
Back in the 1980’s I was chatting with a woman archeologist in an East Coast bar. She said out in California she had taken part in a dig where they found human/hominid? remains suspected to be 200,000 to 300,000 years old. Yes, that old! But the information was apparently being supressed, disrespected, etc. She was pissed.