People ki for the imple reaon that it feel good. Our lip are full of enitive nerve ending, which activate enory area in the brain. Kiing boot the level of neurotranmitter ubtance uch a dopamine, erotonin, and oxytocin. Dopamine trigger craving and deire, erotonin elevate a peron’ mood, and oxytocin i involved in forming emotional attachment.
Beide human, the only animal that cientit have ever een kiing are our cloet ape relative, chimpanzee, and bonobo, and even then it i a rare occurrence. So cientit think there mut be a better explanation for it.
Ki and Tell
Some cientit have theorized that kiing might help u ae a partner’ immune ytem. When people ki, they come cloe enough to ample the cent of each other’ bodie. And that cent may contain clue to immune ytem compatibility.
Parent with complementary immune ytem have children with a h2er ability to reit dieae. Children that are better at reiting dieae are more likely to urvive to have their own children. Evolution will favor thoe who chooe partner with compatible immune ytem over thoe who don’t, even if they don’t even know that they are doing it.
Exchanging aliva may provide other chemical clue to genetic compatibility too. So, kiing really i all about chemitry!