Jelks entered the
University of Texas at Austin in fall 1939. He began his academic career as a pre-med
zoology major, but the Japanese
attack on Pearl Harbor led Jelks to enlist. He joined the
Navy Hospital Corp as Hospital Apprentice First Class and was stationed in
Guadalcanal, where he helped to develop a field hospital for invading American troops. After contracting malaria, Jelks was sent to a Navy hospital in
Auckland,
New Zealand, where he applied for Officers Training. Jelks completed Officers School and was sent to Oklahoma A & M (now
Oklahoma State) to learn Japanese. The war ended shortly thereafter, and Jelks returned to the University of Texas to continue his education under the GI bill. Jelks completed a
Bachelor of Arts in
English (his pre-war minor) and continued to work toward a
Master of Arts (MA) in anthropology. There his coursework focused on North American archaeology and
prehistory, specifically that of Texas. In 1950, Jelks, having fulfilled the requirements for the MA program except his
thesis, was hired by Robert Stephenson as his assistant in the River Basin Surveys program. Jelks completed his thesis and received his MA in 1952. Jelks later returned from archaeological fieldwork to the University of Texas at Austin and earned a
Ph.D. in archaeology in 1965. Familiar with the
direct historical approach, Jelks minored in history while completing his Ph.D., interested largely in the location of
Spanish colonial sites in Texas. Jelks also directed the Texas Archaeological Research Laboratory at the University of Texas from 1958–1965. ==Archaeological career==