Like a Mexican Trump supporter, my libido flagrantly defies all common sense and rationale.

There are times when something extremely arousing is going on and I just shrug and stare blankly at the point just past my partner's head, and other times where nothing sexy is happening whatsoever and I'd probably fuck you if you looked at me funny. It makes no sense. Quit playin' games with my heart.

I'm not alone in this weirdness though; every human female I know has a regular time of the month when she feels most horny. For some, it's during menstruation, which makes no logical sense. For others, it's during ovulation, which makes perfect logical sense. For others still, it's only the second Tuesday of every month, before dinner but after lunch.

What's behind these monthly fluctuations, and why are they so different for every woman?

The answer lies our monthly hormonal cycles. As humans evolved, we stopped going into heat like our primate ancestors and started developing the ability to be fertile for longer, more regular periods of time. Enter the menstrual cycle, the monthly red tide that gives humans a semi-unique ability to fuck all month long in order to increase the likelihood of procreation.

Within the menstrual cycle, there's a period of peak fertility called ovulation when a woman's egg is released from its carton and is more likely to run into any incoming sperm. This is when a little over half of women experience the highest libido and peak erotic motivation. Makes sense; the more fertile you are during the month, the hornier you should be. After all, humanity is nothing more than an innate evolutionary drive to create pooping babies with post-ironic Instagram filter names.

At this point, horny dudes are all like, "When's ovulation, bro?"

Shut up, Kyle. I'll tell you.

Typically, it's on Day 11-21 of the menstrual cycle, or about 14-16 days from you last period.

Tons of studies have confirmed that female libido blasts off during this time, revealing such important facts as:

  • Women masturbate more during ovulation.
  • Compared with menstrual women, ovulating women are ranked more attractive by heterosexual men.
  • Hornier, ovulating women tend to sway their hips when they walk more.
  • Fertile babes put more effort into their appearance during ovulation; spending more time on hair, makeup and outfit choice than during other times of the month.
  • Women’s sexual fantasies and interest in sex, erotic art, and buff, muscular men all increase around the time of ovulation.
  • Women are more open to hooking up with a stranger or acquaintance during ovulation.
  • Lesbian women shore a greater motivation to fuck other women, and bisexual women show a smaller, but still greater-than-average desire for the same.
  • Ovulating strippers make an average of $30 per hour more than strippers on their period, and an average of $15 more per hour than strippers who aren't on their period, but also aren't ovulating.

What's more, is that men even seem to be able to tell when their partner is ovulating, albeit imperfectly.

No one knows exactly how guys sense when females are more fertile (the prevailing hypothesis is pheromones), but several studies have found women report that men become more attentive and jealous around fertile days. One 2006 study published in Evolution and Human Behavior found that when women were ovulating and horny, their male partners saw other men as a greater threat to their dominance. Other studies report slight changes in female's facial appearance during ovulation which might signal fertility to men; a slight flush, a brightening of the skin and an ever-so-slight plumping of the lips were all found to be observable signals that a woman might actually think about mercy-fucking you. No research yet as to whether lesbian woman sense the same things, but given that women know how to speak to each other, I'd assume they'd just ask.

But, the miracle of libido-enhancing ovulation isn't universal. One Australian study asked 173 college-age women to rate their arousal to various sexual fantasies and found that the women showed no significant cyclical differences. In fact, the researchers noted “a high level of stability [in arousal] across the menstrual cycle.”

Another study found that nearly half of women actually prefer sex during their periods. Their horniest time of the month was the time they were least likely to get pregnant, which really muddles all the research on ovulation arousal. However, studies show that female pussy areas are more engorged with blood during menstruation, and while estrogen and progesterone are at their lowest levels then, testosterone begins to spike about halfway through the bloodshed, both of which give chicks a little natural head start on getting horny. That explains why some women find themselves craving sex at the time they should be thinking about it the least.

To recap: most women are horniest around ovulation, although some prefer a monthly bloodbath and Australian women are just horny all the time.

What accounts for these differences? Only the fact that there are about 323,124 confounding factors that affect female arousal outside of her menstrual cycle, the most important of which are birth control, stress and how long a woman's been dating the same person. Women taking the pill, women who are stressed at work, and women in long-term relationships all show no change in arousal across the month, and even tend to report lower sex drives as well.

So if you've got XX chromosomes and you can't account for why you're horny and when, look to some other area in your life other than your menstrual cycle for answers. And if you're a guy and all this only made you more confused, well, welcome to how women feel about your balls.

TL:DR? Some women, like yours truly, are complete and utter slaves to our hormones. Others have a more complicated situation going on that overrides hormonal influence. Either way, those forces are often beyond our conscious control. The best we can do to understand them is to pay attention to our own arousal cycles, fuck everything that moves when they peak, and avoid naming the result of that fucking after an Instagram filter. Lookin' at you, X-Pro II.