“On February 25, 1866, miners claimed to have found a human skull in a mine, beneath a layer of lava, 130 feet (40 m) below the surface of the earth, which made it into the hands of Josiah Whitney, then the State Geologist of California as well as a Professor of Geology at Harvard University. A year before the skull came to his attention, Whitney published the belief that humans, mastodons, and elephants coexisted; the skull served as proof of his convictions.” https://en.wikipedia.org/wiki/Calaveras_Skull