Hay, you! The humble, unsuspected source of the modern world

We have many fancy theories to explain the rise of civilization as we know it.  It was thumbs that led to tool use, that led to agriculture, that led to settled populations.  But no! It was the brain and its ability to enable hunting or gathering parties and war strategies, that led one group to gain control and grow at the expense of others.  No!  It was our longevity that evolved so we could take care of our relatives and more of us could live in the population at any time.  No, no, no!  It was the domestication of draft animals.  No again!  It was the Foxp2 gene and the capacity it gave us for language. No, not that! It was how some races became more intelligent than others, and could live in colder climates than in our African homeland....and thus conquered the world with advanced civilizations.  Yes?

Well, no!  It was after all just the result of a weed, that had nothing to do with our evolution as smart and facile beasts.  What made the world as we know it was hay.  It's the Hay Theory of History, as described by the physicist Freeman Dyson (and cited by ecologist John Lawton on BBC Radio 4's The Life Scientific the other day -- and Freeman says he got it from someone else, who surely got it from someone else):

The most important invention of the last two thousand years was hay. In the classical world of Greece and Rome and in all earlier times, there was no hay. Civilization could exist only in warm climates where horses could stay alive through the winter by grazing. Without grass in winter you could not have horses, and without horses you could not have urban civilization. Some time during the so-called dark ages, some unknown genius invented hay, forests were turned into meadows, hay was reaped and stored, and civilization moved north over the Alps. So hay gave birth to Vienna and Paris and London and Berlin, and later to Moscow and New York.

The idea is that the Roman Empire didn't need hay (and thus didn't have hay) because grass could grow all year in the Mediterranean climate, and so horses could always be put out to pasture.

Trajan's column, Rome

This theory doesn't go entirely unchallenged, as you might imagine.  See this thread on the theory from 2005, e.g., in which one commenter cites no less an expert than his cousin, said to be an authority on Roman history.  Cousin X was thoroughly unconvinced and among other challenges, said this:

Cato the Elder (234-139 BCE), makes mention of hay in his 'De Agri Cultura', LIII, in a fairly offhand manner, indicating that this is no new-fangled or exotic process:

"Cut hay in season, and be careful not to wait too long. Harvest before the seed ripens, and store the best hay by itself for the oxen to eat during the spring ploughing, before you feed clover."

Panel from the Trajan tower, depicting haystacks

Indeed, a column, erected in AD 113, was built to commemorate the emperor Trajan, who ruled the empire from AD 98-117, and his  victory in the Dacian wars.  It's decorated in a spiral bas relief, and the very first panel shows what seem to be hay stacks (on left).

So, another theory about the rise of civilization bites the dust.  But it does sound good ... until you probe a bit. (And, incidentally, we couldn't find a cousin who would comment.)

If there is a serious point to be made it is how easy it is to make up a simple one-factor story to explain a complex event/occurrence/trait. Causation in human life is regularly so complex and indirect, and changeable, that we should not be surprised to find weak prediction from things we think we know, and concomitantly, regular discoveries of things with major effect that we hadn't suspected, which is why the Hay Theory of History can sound so appealing, as well as all the theories we cited above -- and all those gene 'for' disease or trait discoveries that come and go. One factor may be first, or important, but it leads other factors to develop or to other changes that then become causal factors in a continuing cultural evolution. That's how life really is.

Hay, you wouldn't be here otherwise!