Have you ever experienced that magical moment when you meet someone new and it feels like you’ve known them forever? Maybe it’s happened to you with a new classmate, a colleague, or even a stranger you encountered in an unexpected place — a pub restroom, perhaps? In those first moments of meeting them, there’s an inexplicable connection — an instant click. Conversations flow effortlessly, your vibes match immediately. There’s chemistry. It’s what we fondly refer to as a click friendship. For years, scientists have been on a quest to unravel the mystery behind these instant connections: why do we click with some people instantly? What hidden cues lead to forming such bonds?  It turns out that we may not be all that different from our furry friends in this matter. You may have noticed the intricate ritual of sniffing and scent-sharing that occurs when two dogs meet for the first time; it’s a ceremony that decides whether to reposition into a friendly play pose or bark aggressively. It’s not just dogs though; most land mammals rely on olfactory information to assess potential friends and foes. Researchers at the Weizmann Institute wondered: Do humans also sniff each other subconsciously to decide whether they can be friends? In a study published in Science Advances, they showed that this may indeed be the case: people who smelled similar were more likely to hit it off than those who didn’t. Yes, you read that right — our noses might play a much bigger role in our friendships than we imagined. Friends who instantly clicked smell similar The scientists conducted this study on 20 non-romantic same-sex friend pairs who mutually described their first encounter as a click friendship. They collected the participants’ body scent-containing T-shirts and sampled them using an instrument called an electronic nose (eNose). An eNose is a smell-detecting device containing various metal oxide sensors capable of detecting different volatile chemicals. When exposed to a mixture of volatile molecules that make up a smell, the molecule-sensor interactions create a unique pattern of electrical signals, thereby allowing us to record a smell fingerprint of the sample. Using the eNose, the researchers discovered that click friends exhibited more chemical similarity in their body odors compared to random pairs. To confirm this, the scientists called on professional smellers — individuals with a heightened sense of smell. The smellers were given randomized pairs of scent-containing T-shirts and asked to rate their similarities. The smellers’ results were in agreement with the eNose: click friends indeed smelled more similar to each other than random pairs. Body scent can predict whether strangers click with each other These results raised a fundamental question: if friends smell more similar than random pairs, can we predict whether two strangers could hit it off based on body scent alone? To explore this, the researchers devised an experimental set up. They recruited strangers, engaged them in interactions to identify pairs that clicked and those that didn’t, and then analyzed their smells using the eNose. To determine whether an interaction clicked or not, the researchers used the Mirror Game, a tried and tested imitation exercise to study non-verbal interactions between people. The exercise is based on the principle that coordinated body movements often reflect relationship quality and outcome. In the study, two strangers were asked to stand face-to-face at a close distance so they could subconsciously smell each other, and try to mirror each other’s hand movements. Based on scores for synchrony and whether they mutually reported a click, the researchers identified click and non-click pairs. They then performed eNose analyses of all the participants’ body scents. To their surprise, they found that the strangers who reported clicking with each other had significantly more chemical similarity than the ones who did not click.  In other words, the eNose could predict with ~ 70 % accuracy which individuals would click from their body scents alone! These findings shed light on an interesting facet of human behavior: just as we gravitate towards friends who bear visual similarity to ourselves, it seems that we are also naturally drawn to those who smell like us. Click friends smell similar, and strangers who smell similar are more likely to hit it off than those who don’t share scent similarity. So there’s indeed chemistry in social chemistry! It makes you wonder whether we also pick romantic partners based on scent similarity. Could we have gotten the old adage wrong — perhaps it’s not love at first sight but love at first sniff? Dr. Gauri Binayak Ph.D., Dept. of Biology, Indian Institute of Science Education and Research (IISER), Pune About the author: My curiosity about the world led me to the world of science for higher education. During my Ph.D., I realized that the research we do remains understood only by a small community. To the general public, science remains a mysterious realm inhabited by strange white coat-wearing species who mix fumy chemicals and speak in complicated language. I have become deeply interested in bridging this gap through content creation.

If you are a fan of The Office, you would surely be familiar with the proverb “The enemy of my enemy is my friend.” Who can forget a smirking Dwight Schrute using this logic to plot against a colleague in an iconic scene from the hit comedy TV series? Perhaps the most historic illustration of this proverb was during World War II, when two notorious adversaries— the United States and the Soviet Union— joined hands to fight their common enemy, Nazi Germany. Well, you may be surprised to know that forming unlikely partnerships to tackle a shared enemy is not just a clever strategy in politics and high school gossip gangs. For farmers, forming alliances with crop pests’ natural predators could be a game-changing strategy to save their crops from these troublesome bugs. Insect herbivores are one of the peskiest perils in agriculture. These pests are always lurking around, waiting for the right time to steal a meal from plant leaves, fruits, and roots. Whether they feed by chewing plant parts, sucking sap, or boring tunnels in fruits, they wreak havoc on crops. Unlike us fortunate animals who can simply swat away hungry mosquitoes encircling our bodies, plants don’t have the luxury of movement to shoo away insect pests. Being rooted in the same place for their entire lives, they can be severely damaged or killed by such hungry attackers, leading to devastating crop losses in agriculture. Traditionally, farmers have heavily relied on pesticides to manage these infestations. However, amidst the growing concern over their environmental and health safety and the development of pesticide resistance, researchers are exploring another solution: teaming up with the insects’ natural enemies to kill these pests and protect the plants. Forging friendships with fungi Entomopathogenic fungi— fungi that infect insects— are a fascinating group of microorganisms that regulate insect populations in natural ecosystems. Some common examples that can attack a variety of insects are species of Beauveria and Metarhizium. These fungi are specialized to derive nutrients for growth by attacking and killing insects. Since they do not infect plants, they have gained significant interest as allies to crop growers looking to eliminate insect pests. When entomopathogenic fungi’s spores land on an insect’s body, they germinate into hyphae that penetrate the insect’s tough chitinous exterior using cuticle-degrading enzymes. The battle for life between the two commences; the hyphae bore their way into the internal body cavity and rapidly propagate there. The insect’s immune system tries to attack the fungal cells while the fungus counter-defends with toxins, immunity suppressors, and specialized metabolites that go unrecognized by the insect’s immune system. The battle continues until the pathogen ultimately kills the insect. Soon after, the hyphae grow outwards from the body cavity and over the cadaver’s exterior, where they sporulate and can spread to other insects (Figure 1). Many entomopathogenic fungi can infect insects throughout their life from eggs to adults. This is particularly advantageous as they can be used in fields to effectively control pest populations at all different developmental stages. Figure 1. (A) The tree-boring beetle, emerald ash borer (Agrilus planipennis) (Wagner and Turo, 2015). This invasive pest causes economic losses by attacking and killing commercially important ash trees. (B) This emerald ash borer was infected by the entomopathogenic fungus Beauveria bassiana in field trials (Dara et al., 2019). After invading the beetle’s cuticle and multiplying inside its body cavity, the fungal hyphae extend outwards to emerge from the insect body (visible as white masses), and will soon cover the cadaver. Studies are underway on how we can sustainably leverage these fungal allies to mitigate insect pests and protect crops. Some species of Beauveria and Metarhizium already show promise. However, a major practical obstacle when spraying fungal spores on crops is that the spores require moisture and high humidity to germinate and spread. In field conditions, this is often difficult to achieve because spore-containing formulations lose water and dry out in the hot environmental conditions. To solve this problem and create a friendlier environment for spore germination, scientists recently designed a formulation that can meet the fungus’s moisture needs even in low-humidity environments. The research group developed a superabsorbent paste-type formulation containing cellulose and xanthan gum among other ingredients. This paste was highly efficient in absorbing and retaining water, keeping fungal spores sufficiently moist for high sporulation even under 40% relative humidity. Although a few previous attempts were made to design such water-retaining formulations, these relied on synthetic non-biodegradable polymers. In comparison, this novel cellulose-xanthan-based formulation’s biodegradability is a highly advantageous feature. Teaming up with the enemy’s enemy is a promising approach for mitigating pests and protecting our crop plants while minimizing toxic environmental impacts. This strategy has also garnered interest in solving other insect-related problems, including the control of human disease vectors such as mosquitos. As researchers continue to explore ways to harness the power of biocontrol, here’s hoping for a near future where our fruits and vegetables aren’t soaked in layers of pesticides! Dr. Gauri Binayak Ph.D., Dept. of Biology, Indian Institute of Science Education and Research (IISER), Pune About the author: My curiosity about the world led me to the world of science for higher education. During my Ph.D., I realized that the research we do remains understood only by a small community. To the general public, science remains a mysterious realm inhabited by strange white coat-wearing species who mix fumy chemicals and speak in complicated language. I have become deeply interested in bridging this gap through content creation.