The Hohokam Dig

From where had these attacking Indians come? Out of a long forgotten and dim past? Had their medicine man seen the one supreme vision?
At first they thought the attack was a joke. And then they realized the truth!
At first the two scientists thought the Indian attack on them was a joke perpetrated by some of their friends. After all, modern Indians did not attack white men any more.
Except that these did.
George Arthbut and Sidney Hunt were both out of New York, on the staff of the Natural History Museum. George was an ethnologist who specialized in what could be reconstructed about the prehistoric Indians of North America, with emphasis on those of the Southwest. He was a tall, lean, gracious bald man in his early sixties.
Sidney was an archeologist who was fascinated by the ruins of the same kind of ancient Indians. Medium-sized, with black hair that belied his sixty-five years, he and George made an excellent team, being the leaders in their field.
They had come west on a particular bit of business this spring, trying to solve the largest question that remained about the old cliff dwellers and the prehistoric desert Indians, both of whom had deserted their villages and gone elsewhere for reasons that remained a mystery.
One theory was that drought had driven them both away. Another theory ran to the effect that enemies wiped them out or made off with them as captives. Still another supposition, at least for the Hohokam desert people, the builders of Casa Grande whose impressive ruins still stood near Coolidge, had to do with their land giving out so they could no longer grow crops, forcing them to go elsewhere to find better soil.
No one really knew. It was all pure guesswork.
The two scientists meant to spend the entire summer trying to solve this riddle for all time, concentrating on it to the exclusion of everything else. They drove west in a station wagon stuffed with equipment and tracking a U-Haul-It packed with more.