IMHO, I'd date the concept of artificial life further back than Christopher Langton. I'd start with Von Neumann's Theory of Self-Reproducing Automata. Though the book was published in 1966, Von Neumann was working on the concept as early as the 1940s. In his work,

"He asked what is the threshold of complexity that must be crossed for machines to be able to evolve. His answer was to specify an abstract machine which, when run, would replicate itself. In his design, the self-replicating machine consists of three parts: a "description" of ('blueprint' or program for) itself, a universal constructor mechanism that can read any description and construct the machine (sans description) encoded in that description, and a universal copy machine that can make copies of any description." From wikipedia [1]

[1]. https://en.wikipedia.org/wiki/Von_Neumann_universal_construc...