I like to think I have a decent amount of self-control when it comes to snacking. But put any sweet-meets-salty treat in front of me—like yogurt-covered pretzels or chocolate-dipped potato chips—and suddenly I turn into a leggings-clad Cookie Monster, leaving behind nothing but an empty bag and a few crumbs.

To be clear, it’s only the combination of sweet and salty that I can’t resist. I don’t care for straight-up savory snacks, like plain pretzels or chips, and can only eat a few bites of a sugary dessert without feeling nauseous. Judging by the number of hybrid flavors at the grocery store right now, from salted caramel ice cream to Chicago-style popcorn, I’m not the only one who’s obsessed. So what’s up with that?

In a quest to find out why salty-sweet snacks are so damn addicting, I first called upon food historian Sarah Wassberg Johnson. She confirmed that the roots of this pairing go way back, long before the peanut M&M was born. “Sweet and savory combination foods were quite popular in the ancient Middle East and later in Medieval Europe—mostly meat cooked with fruit and, particularly during the Medieval period, with sweet imported spices like cinnamon, mace, allspice, and nutmeg,” she says. (Hmm, def less appealing than PB-filled pretzels.) Candied salted nuts and other desserts were also a thing back in those days, she adds. These were mostly restricted to the wealthy, however, since refined sugar was hard to come by.

So, clearly, this isn’t a food trend that was dreamed up in a lab—it’s something we’ve always been drawn to. Part of this is because of evolution, says Angelina Schiano, a graduate research assistant at North Carolina State University’s Sensory Service Center. “We do have an innate preference for sweet and salty foods,” she tells me. “From day one, babies love sweet foods, which makes sense because mother’s milk is essentially sweet.” She says our love of salt develops next, once we’re around four months old. That’s likely connected to development—scientists have a theory that we’re drawn to salty things because they’re found in essential minerals that we need for growth, like sodium and potassium.

We’re also conditioned to like certain flavor profiles because of what we’re exposed to—and that again starts really, really young. If a mother eats lots of sweet-and-salty foods while she’s pregnant or breastfeeding, studies show that her baby will be likely to enjoy those types of foods, too. (This is generally true of all foods that moms eat while breastfeeding.) The same goes for formula-fed babies—they’ll be most drawn to the flavors in the formula they were first exposed to, says Schiano.

But that’s not the extent of the science behind salty and sweet. It turns out that sweet things are actually more irresistible when paired with a little sodium. “Salt enhances our perception of sweetness and also our perception of other aromatic flavor compounds in our food,” explains Schiano. Which is why adding a few flakes of sea salt onto a chocolate chip cookie is *chef’s kiss.*

So now you know why you can’t stop eating candied bacon and chocolate-chip trail mix: It’s not about willpower, it’s about biology. But obviously, you don’t want to go too HAM on the sodium and sugar, because overdoing both can have some nasty health implications. Luckily, it’s 2019 and healthy alternatives abound—like these vegan “peanut butter cups” that I most definitely will not be sharing.

If you’re on a road trip, here are the gas station snack options you should go for—and these are the three tips to keep in mind if hunger strikes late at night.