If you think about it, shaking hands is a bit of a strange idea. But as long as anyone can remember, people have always been grasping hands, and shaking up and down as a way to meet and greet each other. Theories of the origins and reason for the handshake are extremely varied.

This practice may even date back to around 1800 BCE in ancient Babylon. In Babylon at this time, it was believed that the gods could transfer power to a human through clasping hands. This is why every year at the New Year’s festival, the king would grasp hands with a statue of a god, and it was believe that the god’s power would be transferred to the king for the next year.

Another theory is a bit more logical and survival-based. It is believed that the ancient Romans would extend their hands when meeting another person to ensure them that you were not carrying a weapon in your hand. The Romans also may have clasped arms so they could check if weapons were up the other’s sleeve. This practice evolved in medieval times, where the acquaintances would clasp hands and shake as we do today. This was meant to shake out any hidden weapons that the other might have up their sleeve. This seems similar to today’s practices in which we shake hands to establish trust when meeting someone new.

The third, and most interesting theory is based wholly in science. At the Weizmann Institute of Science in Israel, researchers found that people instinctively smell their hands after shaking hands with someone. They found this by filming 271 subjects as they were sat down in a room, then an experimenter came into the room and shook their hand, and then the experimenter left again. These subjects were unknowingly filmed and the amount of times they touched their face was recorded from one minute before the experimenter entered the room until one minute after the experimenter left. The study found that the subject smelled their hand 100% more after they shook hands with the experimenter than they did before shaking hands. Some subjects were also equipped with an apparatus that recorded their nasal air flow during the experiment. They found that large inhales (sniffs) coincided with the time when the subjects touched their faces. This means that the subjects were in fact smelling their hands. They also found that when the subject shook hands with someone of the same gender as them, they were more likely to smell their right hand (the shaking hand), and when the subject shook hands with a person of the opposite gender, they were more likely to smell their left hand (the non-shaking hand). This study may lead us to believe that humans, like animals may receive information through pheromones and chemosignals by smelling each other. But this study also raises many questions to be answered. Why do we smell the opposite hand when shaking with the opposite gender? Is this mechanism possibly intended for us to scope out our competition within our gender? Does sexual orientation affect the outcome of a study like this? Would the results be similar if we shook hands with our left hands? All of these questions could be answered by future studies that should be implemented to further understand this strange instinct.

Whether you believe that the custom of handshaking came from the Babylonians, the Romans, the medieval knights, or our neanderthal ancestors who wanted to smell each other in a more classy way, handshaking is deeply rooted in human history. Possible reasons for handshaking include religious ceremonies, self-defense, and smelling each other. The next time you shake hands with someone new, notice if they touch their face within the next minute or so. Your new friend just might be trying to catch a whiff of your pheromones.

Sources:

Weapons, History 1, History 2, History 3, TIME Article, Study