People shake hands as a universal signal of peaceful intentions, trust, and willingness to cooperate. What feels like a simple social reflex actually has roots stretching back thousands of years, and the reasons behind it are more layered than most people realize. The gesture serves purposes that are historical, psychological, and even biological.
Ancient Origins of the Handshake
The handshake appears in artwork and artifacts from ancient Greece, where it was known as dexiosis. Rather than a casual greeting, dexiosis carried real symbolic weight. It represented a permanent bond between people, emphasizing family ties and social connection. It also appeared in scenes of farewell, marking significant moments of departure or transition. The gesture’s roots reach back to the Archaic period of Greek civilization, making it one of the oldest recorded social rituals still in use today.
The most popular theory about the handshake’s practical origin is straightforward: extending an open right hand proved you weren’t holding a weapon. In a world where strangers could easily conceal a blade, clasping someone’s sword hand was a quick way to establish safety. The up-and-down pumping motion we associate with a modern handshake is believed to have been added during the Middle Ages, specifically to dislodge any daggers hidden up a sleeve. Over centuries, this security check softened into a gesture of greeting, friendship, and agreement.
A Primate Instinct for Reducing Tension
Humans aren’t the only primates with rituals for smoothing over tense social encounters. Among monkeys and apes, mutual grooming serves a similar function. Allogrooming, where one animal grooms another, goes well beyond hygiene. It reduces anxiety, strengthens social bonds, and helps establish trust within a group. Primates groom each other more frequently in situations involving competition or conflict, using the behavior as a tension-reduction mechanism when the outcome of a social encounter is uncertain.
The handshake fills a remarkably similar role in human life. When two people meet for the first time, there’s a natural flicker of social uncertainty. Reaching out and making physical contact dissolves some of that tension instantly, functioning as a quick, ritualized way of saying “I’m not a threat” before a single word is spoken.
Your Brain Is Secretly Sniffing
One of the stranger discoveries about handshakes comes from researchers at the Weizmann Institute of Science, who found that the gesture likely serves an unconscious biological purpose: transferring and sampling chemical signals between people. Social chemicals on our skin carry information about identity, mood, and even reproductive status. A handshake moves those chemicals from one person’s hand to another’s.
Here’s where it gets surprising. After shaking hands with someone of the same gender, both men and women held their right hand (the shaking hand) near their face for longer than people who hadn’t shaken hands. After shaking hands with someone of the opposite gender, they spent more time with their left hand near their face instead. In both cases, hands consistently drifted to the area around the nose. When researchers measured airflow, they found that nasal airflow more than doubled when a hand was near the face, confirming that people were actively sniffing their hands without realizing it.
When experimenters applied specific chemical signals to their hands before shaking, the sniffing patterns of volunteers shifted in response, with different chemicals producing different behaviors. The implication is that handshakes are, at least partly, an olfactory sampling ritual. You’re gathering chemical information about the person you just met, all without any conscious awareness.
How Handshakes Build Trust and Cooperation
The psychological effects of a handshake are measurable and significant. Research published through APA PsycNet found that during negotiations, pairs who shook hands at the start achieved better joint outcomes than those who didn’t. The handshake functions as a signal of cooperative intent. People who received a handshake expected their partner to behave more cooperatively, and that expectation shaped the entire interaction that followed.
This effect held up even in tougher, more adversarial negotiations. Executives who shook hands before a competitive negotiation were less likely to lie about information that would benefit them, increasing cooperation even at personal cost. Interestingly, the signaling works in both directions: when a handshake came from someone who was visibly sick, it actually reduced cooperation, because the gesture now signaled something other than goodwill. The meaning people assign to the handshake matters more than the physical contact itself.
First Impressions in Job Interviews
The quality of your handshake carries real weight in professional settings. A study of 98 mock job interviews found that handshake quality was directly related to interviewer hiring recommendations. Five independent raters evaluated each handshake, and the ratings predicted interview outcomes even after controlling for differences in physical appearance and how candidates were dressed. The handshake essentially mediated the effect of a candidate’s personality on the interviewer’s perception.
One notable finding: while women in the study received lower handshake ratings on average, they did not receive lower employment suitability scores. Exploratory analysis suggested that a firm handshake may actually carry more weight for women than for men in shaping interview outcomes, potentially because it challenges default expectations.
Handshakes Transfer More Than Trust
There’s a practical downside to the handshake. Researchers at Aberystwyth University tested how much bacteria transfers during different greetings by coating a gloved hand in E. coli and performing handshakes, fist bumps, and high-fives. A handshake transferred roughly 10 times as many bacteria as a fist bump. The reason is simple: a handshake involves more skin contact over a longer duration, giving microorganisms more opportunity to move between surfaces.
This finding gained real-world traction during the COVID-19 pandemic. A study of 152 hospital doctors found that before the pandemic, 94% greeted outpatients with a handshake. After the pandemic, that number dropped to 23%. Among doctors who changed their greeting habits, 73% cited infection control as the reason. The handshake hasn’t disappeared from medical settings, but it lost its default status in a way that may be permanent for some professionals.
What a Good Handshake Looks Like
According to the Emily Post Institute, a handshake should last about two to three seconds, with one or two gentle pumps. Your palm should face sideways in a vertical position. Turning your palm downward can come across as dominant, while turning it upward can seem submissive. Using both hands to clasp the other person’s hand is generally best avoided in professional contexts, as it can feel overly intimate or performative.
The specifics matter less than the intention behind them. A handshake works because both people understand what it means: I come in peace, I’m willing to cooperate, and I acknowledge you as someone worth engaging with. That core message has remained remarkably stable across thousands of years, even as the gesture evolved from a weapon check into a boardroom ritual.