Very much in the eye of the beholder, don't you think?
I once read a book by an archeologist who claimed human beings were in the San Diego region of California during the warm period preceding the last ice age - that is tens of thousands of years before the conventional dates. His evidence was what he called hearths and stone tools that he had found on the slopes of the hills there (which would have been sea side at the time, since the oceans were higher). But other scientists scoffed and said his hearths were indistiguishable from accidental burnings, and his tools were just common pebbles, fondly looked at. I haven't heard any more about his theory for the last thirty years.
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