Rachel Charlene Lewis
Updated Aug 06, 2016 @ 8:34 am
Credit: Getty / LOIC VENANCE

Ah, periods. Some find them empowering, some find them to be a near-death experience, and others just remain baffled by one single question: why is there SO MUCH BLOOD? Luckily, the folks of Broadly stepped forward to take on this query, and have returned with an answer that, actually, is pretty rad.

Anthropologist and researcher Dr. Elizabeth Rowe explained the “why” behind our messy Aunt Flow visits.

The science behind our periods

“The tissue that is lost during menstruation is a mom’s way of keeping the fetus in check—it’s like an evolutionary balance.”

The blood we lose during our periods is what would have been used to nourish and sustain a fetus. Since we didn’t get pregnant, though, it’s all just rushing freely from our bodies. See? It’s not just for ~funsies!~ Bleeding loads and loads during our periods is an evolutionary trait to protect our fetus, and, well, protect us from the fetus.

It’s actually connected to prep for pregnancy

“In animals that bleed during pregnancy, the fetus digs deeply into a mom’s uterus so it can have access to her blood supply. The problem with that is, if you’re a mother mammal — if you let a fetus just dig into your tissues willy-nilly, that could ultimately kill you.”

Well that’s only a little bit terrifying. But when is science not a little terrifying?

So it has a lot to do with our aggressive fetuses

“The tissue that is lost during menstruation forms something of a shield between fetus and mom. I call it pre-gaming for pregnancy. It turns out you don’t see menstrual bleeding in species where they don’t have an aggressive fetus.”

Essentially, humans have fetuses that aren’t inherently going to stop themselves from draining us of all of the good stuff we need to stay alive. Nope, they’d take it all for themselves to improve their livelihood, or so they imagine. By having massively bloody periods, we’re really just protecting ourselves, since this means our uteruses become *super* loaded with blood when we’re pregnant, saving us from these nutrient-hungry fetuses.

It’s definitely the least fun pre-game we’ve ever been to, but at least we now understand why it goes down!