Sweaty palms, quickened pulse, decreased appetite...
No, it's not the stomach flu — it's love!
For most of the animal kingdom, the idea of love doesn't exist. Sure, there are some pretty interesting courtship displays, but those are more for the male to prove he's healthy and strong and would make a good mate.
Humans, on the other hand, tend to have relationships that are more romantic in nature. It may often be described as a matter of the heart, but when it comes to love, it's all about the brain.
A bunch of chemical reactions in the brain may not sound very poetic, but it's actually quite beautiful. Deep in the hypothalemus, the part of the brain responsible for emotion, the autonomic nervous system is stimulated faster than you can say "Adele." This opens the floodgates for hormones and other signals in the body to become more receptive to mating, but also cause feelings of love as well.
One of the hormones released during this process is oxytocin, which binds to the reward center of the brain. Essentially, love becomes like an addiction to a drug. Contact causes elation, just like a high. When the person you love is away, withdrawal can cause heartsickness.
Not only does oxytocin cause happiness and warm, fuzzy feelings, but it's also involved in establishing trust. One study found that individuals who had higher levels of oxytocin were more likely to remain monogamous.
There are several theories about why humans evolved the ability to love romantically when it's so rare in nature. One idea is that loving bonds helped provide incentive for cooperation in social groups, which increases the odds of survival, particularly for infants.
Check out SciShow's beautiful explanation of the chemical origins of love here:
Want those awesome scientifically-correct Valentines for your loved one? Get them here.
Cover image: Shutterstock