When Richard S. Shaver was working as a welder in the early 1930s in a Ford factory in Wisconsin, he claimed to hear voices warning him of vast caves under the earth, in which lurk the dero: prehistoric, devolved cannibals who prey on our minds with ancient super-science.
In 1944, Shaver wrote this story which was later reworked and published in the March 1945 issue of Amazing Science Fiction.