Curtis Connors was a gifted surgeon who enlisted in the U.S. Army and was sent off to war. He performed emergency battlefield surgery on wounded GIs, but his right arm was injured in a blast and had to be amputated. After his return to civilian life as a research technologist, Connors became obsessed with uncovering the secrets of reptilian limb regeneration. Working from his home in the Florida Everglades with the help of war buddy Ted Sallis, he finally developed an experimental serum taken from reptilian DNA. He successfully regrew the missing limb of a rabbit and then chose to test it on himself. Connors ingested the formula and his missing arm did indeed grow back. The formula had a side effect; Connors was subsequently transformed into a reptilian humanoid monster.