also keeping grain reserves was probably the killer application of ancient civilizations; (you can also read about that in the Bible - on Joseph and his brother

also keeping grain reserves was probably the killer application of ancient civilizations; (you can also read about that in the Bible - on Joseph and his brothers), being able to weather the occasional famine was probably worth much more than the increased risk of disease in crowded and dirty cities or the cost of bondage/servitude (in these times that is) - alternatively it may be that this perception was a matter of perceived risk vs. known risk; the certain risk of famine had more weight than the uncertain risk of disease and loss of freedom; hard to say. But these are all speculations.