Galactic Derelict1959
by Andre Norton
Galactic Derelict, is the second novel of The Time Trader series. It continues with the premise of an encounter between Western Heros and a mysterious alien race that has used time travel to alter earth. This novel shifts, between present day and the time of Folsom Man, some 10,000 years ago.
— from OpenLibrary
13 editions at OpenLibrary