An icebreaker
A Boston University geologist argues that weathering patterns on the Great Sphinx and its enclosure point to rainfall, not wind, pushing its true age back thousands of years before Egypt's traditional dynastic timeline. Egyptologists and most geologists reject the redating.
After examining the site in 1990, he argued the Sphinx enclosure shows rain-formed weathering patterns inconsistent with Egypt's dry climate over the last several thousand years, presenting his findings to the Geological Society of America in 1991.
An independent Egyptology writer invited him to examine the Sphinx's weathering in 1990, having already argued on his own that the monument looked far older than its standard date; the two then presented their case together.
As the leading excavator of the Sphinx site, he has argued there is no chronological or architectural room for a much older monument, and that the soft, layered limestone weathers unevenly for reasons that don't require rainfall or an earlier age.
A geology professor who reviewed the same site, he argued the weathering was better explained by wet sand filling the enclosure than by long exposure to rainfall, a reading that leaves the conventional date intact.