What’s the number one reason we riot? The plausible, justifiable motivations of trampled-upon humanfolk to fight back are many—poverty, oppression, disenfranchisement, etc—but the big one is more primal than any of the above. It’s hunger, plain and simple. If there’s a single factor that reliably sparks social unrest, it’s food becoming too scarce or too expensive. So argues a group of complex systems theorists in Cambridge, and it makes sense.