According to Prof. Herbert Stoyan, probably the oldest GC algorithm description is in 'J. McCarthy, M.L. Minsky: Artificial Intelligence. Quarterly Progress Report No. 53, Res. Lab, of electronics MIT, Cambridge, April 1959.' Prof. Stoyan then mentioned that the 'first garbage collector was implemented by Dan Edwards during June/July of 1959'.

So we have 60 years of GC research.