When 5,000 red-winged blackbirds fell dead on New Year’s Eve in Arkansas, and 500 more in Louisiana, many people immediately looked for a villain. There was speculation about military tests and pesticides, and a lot of wondering whether the bird deaths and other incidents, including the mass deaths of fish, were linked.

Even very plausible explanations did not allay the suspicion that something sinister must be going on. Why? Because we’re human. Our minds have evolved to look for patterns, and causative agents. In fact, some thinkers argue that this turn of mind, which evolved as a survival mechanism, ended up predisposing humans to believe in a deity, because when we can’t find a natural cause for an apparent pattern or event, we posit a supernatural one. Certainly it predisposed us to look for an interesting culprit for the bird die-offs.

One of the writers to suggest how we ended up this way is Michael Shermer, the founding publisher of Skeptic magazine and a Scientific American columnist, who uses a common scenario to explain why we believe in things that may not be there — hominids on the savannah hearing a rustling in the tall grass. The one who thinks, “It’s a lion!” and escapes quickly survives to propagate her genes, thus fostering a kind of protective alarmism in her descendants. Another might think, “There’s always some kind of rustling in the tall grass, it’s probably the wind,” and keep on grooming. If he guesses wrong, the downside is being eaten by the lion. Thus, no offspring and no propagation of the “don’t worry, be happy” genes.

Of course, people have both modes of thought, perhaps because rustling is usually caused by the wind, and the hominid who is too alarmist is always running away from nothing and probably too exhausted and too anxiety-ridden to mate. So there’s room for both the wind and the lion in human minds.