processing before sending on its results through the optic nerve to the cortex. My answer for the greatest invention of the last 2,000 years is still the lens, but the greatest invention of all times is the brain which, incidentally, has managed to figure out how to use the lens it is already hooked up to and the lens it has learned how to build in its never-ending attempt to understand the Universe. I would very much like to add The Plough (or the digging stick ? the principle is the same) to your list of "Inventions ". My thesis is that farming really began at least 40,000 years ago (not 10,000 years ago in the "Neolithic Revolution" as is generally supposed) but that for 10s of thousands of years people 'merely' managed the environment in various ways, while at the same time getting a large propotion of their food by hunting and gathering. This management I have called "protofarming ". In fact you can do all of horticulture (which in effect means cultivation of individual plants, though the etymology means gardens) and pastoralism in protofarming mode. The economic switch came when people came to rely on farming more than on hunting and gathering. The most significant technological shift was the act of breaking the soil ? i.e., cultivating the field ("agri" ? culture) as opposed to the ad hoc management of individual plants and herds of animals, in an essentially wild environment. It is when you break the soil