At http://phys.org/print356795958.html … the consensus view is that farming began in the Fertile Crescent around 12,000 years ago (at the beginning of the Holocene). However, Stephen Mithen, in his opus, 'After the Ice' (Phoenix, 2003) did suggest agriculture was being practised before the start of the Younger Dryas 13,000 years ago (but suffered a temporary relapse) and took off afterwards. The relapse may have been due to a decline in population associated with the Younger Dryas event which altered climate around the world for a thousand years.
The article, in PLOS ONE, an online journal, concerns the discovery in Israel of a camp site on the shores of the Sea of Galilee that was at least semi permanent if not permanent in nature (with some hunting and fishing). They also found evidence of rudimentary agriculture and this was taking place as early as 23,000 years ago. The site was preserved as it had been charred and they covered lake sediments (another example of catastrophic preservation of past life). It was subsequently sealed in low oxygen conditions whichare ideal for preservation of plant material. This included weeds common to cultivation as well as emmer wheat, wild barley and wild oats – plus a grinding stone and evidence of cereal grains prepared for consumption. Sickle blades were also present and evidence for fields in which to grow the cereals. How far back does exploitation of plants go – way back we may suspect.