MacCarthy described EVAL as a theoretical entity; it was Steve Russel who said he would code it. MacCarthy was surprised and said that Russel is misunderstanding it; it's just a theoretical description, not code.
But Russel basically hand-translated the calls into assembly code and got an interpreter out of it.
An interpreter written in Lisp cannot be executed if you don't already have an existing interpreter to run it.
The key insight that we can describe the interpreter in Lisp, and then somehow compile it into code belongs to Russel. Eventually it became possible to do that by machine: when you have a Lisp compiler, the Lisp-in-Lisp interpreter can be compiled by machine rather than by hand.
But Russel basically hand-translated the calls into assembly code and got an interpreter out of it.
An interpreter written in Lisp cannot be executed if you don't already have an existing interpreter to run it.
The key insight that we can describe the interpreter in Lisp, and then somehow compile it into code belongs to Russel. Eventually it became possible to do that by machine: when you have a Lisp compiler, the Lisp-in-Lisp interpreter can be compiled by machine rather than by hand.