The leaves are falling, it’s sweater weather, and the holiday season is just around the corner. As the temperatures drop, so do the “Hey Stranger” direct messages (DMs) from past flings. This seasonal phenomenon is known as “cuffing season.”

From rapper Fabolous singing about “summer [girls] turning into winter wifeys” in his song “Cuffing Season” to the memes and hashtags labeled “#cuffingseason,” Urban Dictionary accurately describes the term:

“During the fall and winter months, people who would normally rather be single or promiscuous find themselves, along with the rest of the world, desiring to be “cuffed” or tied down by a serious relationship. The cold weather and prolonged indoor activity causes singles to become lonely and desperate to be cuffed.”

Although pop culture has acknowledged this millennial phenomenon, is this based on an evolutionary instinct for humans to mate?

“Psychologically, we are also primed to seek mates in the winter. We also associate the winter holidays (Thanksgiving and Christmas) with family and partners, so we feel particularly lonely, then, on top of our evolutionary drive to seek connection in the winter,” Dr. Scott Carroll, a physician and psychiatrist in Albuquerque, N.M., told Medical Daily.

It’s true that our plus-one invites, family and office parties, and a midnight kiss on New Year’s can add to the social pressure of finding someone. The holidays are often about assessing whether we’re meeting expectations, and families typically want to know if you’re dating, engaged, married — or still married, said April Masini, a relationship expert and author.

“The ‘wonder’ that your family expresses may feel more like interrogation than holiday interest. Bringing a date or starting a relationship is a conscious, and sometimes unconscious, way of abating pressures,” she told Medical Daily.

The Winter Blues

“Netflix and chill,” takes on a whole new meaning during cuffing season. The cultural sex catchphrase, which was introduced to the mainstream this year, refers to a person who invites another into their home to have sex while Netflix streams in the background. And while the term wasn’t introduced during the winter, there seems to be no other time that’s more fitting than cuffing season.

In fact, there’s even evidence to support the idea that we should all get under the blankets and watch movies — specifically romance — during cuffing season. A 2012 study published in the Journal of Consumer Research found physical coldness could activate a need for psychological warmth, which led to an increased interest in romance movies and novels. Thus, it makes sense for Netflix and chill invites to steadily rise throughout the winter months because the desire for warmth yields the desire for romance.

The Most Fertile Season

Evolutionarily speaking, the cuffing months (November and December) are the most fertile season, with birth rates at their highest nine months later, in August and September. Although it’s unclear why so many babies are conceived in the winter and born at the end of the summer, a 2001 study published in the journal Obstetrics & Gynecology suggests it could be attributed to a lower sperm count and concentration from August through October — a result of the summer heart. Interestingly, these numbers rebound in late autumn and tend to exceed baseline values, meaning it's prime baby-making season.

Unlike many other primates, however, humans have not evolved to have a mating season. For most female mammals, an estrous cycle — when they’re “in heat” — causes behavioral and physiological changes that make them more sexually active only once a year to several times a year. On the other hand, women can be sexually active and fertile all year round, and therefore don’t feel a biological urge to settle down in the winter.

Humans don’t hibernate, but “due to survival needs, we have evolved to congregate around shelter to survive the winter,” Carroll said. Similar to their ancestors, females adopt a “survival-of-the-fittest” mentality by accepting a partner who can provide shelter and warmth, to increase their own odds of survival.

So, cuffing season may not be evolutionarily driven, but for many people, the desire to cuff or be cuffed is very real. And while we may not have a mating season, cuffing season may be the closest thing to it.