Charred seeds - not much to look at, but perhaps 10,000 years old
Farming was not a single "invention" - it's now thought it developed gradually over centuries in various places. But the first evidence for it comes from the Fertile Crescent (the arc of land stretching from the Mediterranean to the Zagros mountains, with Iraq - Mesopotamia - as its heartland). The best evidence - recently published (2013) - comes from Iran, from Chogha Golan, a site in the western Zagros, later to be Elamite terrritory.
Khonjan Cham river near Chogha Golan, Ilam, Iran. Photo: TISARP/University of Tübingen
To prove that actual farming was going on, you need plenty of charred seeds, whose species can be identified, and which can be dated accurately. Such evidence has been hard to come by - until the excavation of the mound ("tell") at Chogha Golan. It was continuously occupied from 12,000 years ago until around 9,500 years ago: during this time archaeologists and experts in ancient plants can detect a gradual change in the grains: wild at first, but over time showing evolution towards crops still in cultivation today: barley, various kinds of wheat, lentils and peas.
A handful of charred seeds from the Urartian citadel at Cavustepe, near Van, Eastern Turkey, 8th century BC. Photo AMW
Weed seeds have helped too - the presence of the sort of weeds found in farmers' fields is good evidence that crops were being deliberately sown. Stone implements for grinding and crushing seeds (pestles and mortars, querns) have also come to light (these were still stone-age people: they knew nothing of metal, and did not make pottery - and they were still hunting big animals). Bones reveal that domestication of goats was just beginning at the same time as cultivated cereals were being developed - just as elsewhere in the Fertile Crescent.
It's quite possible that ideas - and maybe even seeds - were exchanged among the various early farmers in the region: in different parts of the Fertile Crescent they were experimenting with different species.
The earlist evidence for the cultivation of lentils (lens culinaris) comes from Tepe Sabz in Iran, and dates from 5,500 - 5000 BC. For more on ancient lentil cultivation in Iraqi Kurdistan see this Guardian article.