Tonight is the night for ghosts and specters, for black cats and vampire bats, and for a night kept alight by the fires of a thousand Jack-o-lanterns.
It's also the night for droves of masquerading children to wander the streets like a horde of rampaging zombies. But don't worry, it's not brains they're after, just candy.
"Trick or treat!" they'll shout with delight, not knowing the history and true meaning behind what they say. This seemingly innocent question is actually a veiled threat: Will you tender a treat or be subject to a trick of comical mischief? From most children, this statement is a hollow one to be sure, but even if it's not, there's really not much to worry about. By the end of the night, these sugar-seeking zombies will be too busy gorging themselves on candy to be much of a threat to anyone besides themselves. Why? They just can't help it.
Over thousands of years, our ancestors evolved to crave these nutrients - salt, because it is necessary to maintain hydration, sugar and fat, because they give us energy. Long ago, these nutrients were often scarce. This Halloween, they are anything but. All you have to do is throw a bed sheet over your head and walk from door to door with your arms outstretched.
Digging deeper, researchers from the University of Melbourne have discovered that salt can be addicting in the same manner as cigarettes. They found that rodents, when deprived of salt, develop the same proteins that cause junkies to crave nicotine. This neurological feature likely served our evolutionary ancestors well, but most people living in developed nations don't really need it.
It's a similar situation for sugar. Our tree-swinging, fruit-eating primate relatives evolved to be drawn to it's sweet taste because the sweeter the fruit, the more calories and water the fruit often contained. Today, humans are still left with the vestiges of that evolutionary trait. Scientists at the Monell Chemical Senses Center have found that our tongue, intestines, and pancreas are all biologically programmed to tell our brains to love sugar.
Lastly, when we ingest foods rich in fat, researchers have found that our bodies produce marijuana-like endocannabinoids that prompt us to overindulge. These substances are theorized to function by initiating the release of digestive chemicals that tell us we're still hungry. When food is scarce, this biological design is perfect for prompting us to store energy.
Fueled by evolutionary tendencies, tonight's trick-or-treaters will undoubtedly binge on candy filled with salt, sugar, and fat. Though they may not be haunted by vampires, ghosts, or werewolves, they will undoubtedly be tormented by a horrible stomachache.