Human beings shake hands for the same reason dogs sniff each other's butts. Well, sort of.
According to the Guardian, a study conducted at Israel's Weizmann Institute of Science found that people (unknowingly) sniff their hands after a handshake in order to detect clues about a person's identity.
A team led by Professor Noam Sobel secretly filmed 280 people before and after they said "hello" to a researcher, sometimes doing so with a handshake.
For about 20 percent of the time in which they were filmed, participants were sniffing their own hands both before and after the greeting.
Unlike rodents, cats and dogs, it isn't socially acceptable to walk up and sniff each other. We think this is a way we've developed to collect this information in a subliminal fashion.
If the researcher and participant were of the same sex, participants spent twice the amount of time sniffing their right hand afterwards.
A handshake from the opposite sex, however, yielded an odd result: Participants were overwhelmingly more likely to sniff their left hand, even though this was not used in the handshake.
The team suggested that this might be a "reassurance mechanism," or a reminder that the participant did not give off a bad smell.
Next, the researchers placed nasal catheters in a second group of participants to confirm they were in fact sniffing instead of just resting their hands near their face.
Handshaking is already known to convey a range of information depending on the duration of the gesture, its strength and the posture used. We argue that it may have evolved to serve as one of a number of ways to sample social chemicals from each other, and that it still serves this purpose in a meaningful albeit subliminal way.
Researchers additionally put on sterile gloves to determine which chemicals are transferred during a handshake.
The two chemicals identified were squalene and hexadecanoic acid, both of which are utilized by dogs and cats for attraction purposes.
While the team could not conclude what people expect to learn by smelling themselves post-handshake, Sobel suggested they may be looking for certain odors that signify qualities pertaining to health or social status.
The study was originally published in the journal eLife.