Food crises caused by ever-rising demand and shortages of supply are not just a modern worry: they have occurred in the past wherever large urban populations have arisen rapidly. One ancient solution to this problem was the reaping machine, developed by farmers in the Roman region of Gaul during the first century AD. The reaper aws needed to cope with the large demand for grain in an area with unpredictable weather during the short harvest season and a local shortage of agricultural labor.

The vallus, as the reaping maching was known to the ROmans, was described by the encyclopedist Pliny in AD 77: "On the vast estates in the provinces of Gaul very large frames fitted with teet at the edge and carried on two wheels are driven through the corn by a donkey pushing from behind; the ears torn off fall into the frame."

Relief sculptures on local Gallic tombstones give further information on how the reaping machines worked. Pliny's "teeth" were rows of very sharp kinfe blades set close together on the leading edge of the cart at a height slightly below that of the heads of grains. The grain fell into a boxlike hopper behind the "teeth." Texts other than Pliny suggest a larger version of the reaping machine, the carpentum which was pushed by an ox.

Yet despite the obvious benefits of a successful mechanical reaper it failed to be adopted widely in the Roman Empire. This may seem particularly strange given that running an agricultural estate as the only career, outside serving in the army, that the upper classes of Roman times deemed worthwhile. Whole manuals on efficient farm management were written for the gentry by Greek, Carthaginian and Roman landlords.

In fact there was nothing about the reaper itself that led to its neglect; rather this was a result of one key factor in Roman life: its slave economy. While the Romans certainly did not lack inventive ability, they did fear change. With their estates farmed by vast numbers of slaves, the danger of social upheaval was always present and might have become acute if slaves started to be displaced by machines. Accordingly the Gallic reaper fell out of use, providing a classic example of an ancient invention that should have had a far greater impact than it actually did.

The mechanical reaper was not used again anywhere until the early nineteenth century, when the ancient Gallic version was to play a crucial part in its reappearance. A description of the Gallic reaper was preserved in the work of Palladius, a fifth-century Roman writer on agriculture. A translation and reconstruction drawing was published in J.C. Loudon's Encyclopedia of Agriculture in 1825, and caught the eye of John Ridley, a young Londer who later emigrated to Australia. There, inspired by an acute labor shortage and the example of the Gallic reaper, he devised his own reaping machine in the summer of 1843. Peter James & Nick Thorpe, "Ancient Inventions," 387.