Imagine you enter a room, you see a stranger there, and your pulse starts to beat more often. Perhaps, you are blushing. Perhaps, you can't take your eyes off him. Time seems to stand still. However, this is not about a sentimental love story. This story is about the latent smell of a person you unconsciously perceive. As it is not the appearance, voice, or behavior that are decisive for the mate's choice, but primarily her or his smell.
Smell acts directly on the most ancient part of our brain, the limbic system - the place of emotions, instincts and unconscious perception. In this part of the brain, our motivations and emotions are formed. It also processes reactions, reflexes and desires, which can have a strong influence on our behavior. Therefore, our first reaction to smells is fast, unconscious and agitated.
Why is this happening? For this, nature has its rationale.
Our genes (HLA genes) determine what fragrance we have. Since all of us have our own unique structure of genes, we all have a distinctive smell. An individual smell is made up of thousands of scent molecules that we exude from every pore of our skin.
From evolutionary biology's perspective, we prefer someone who is genetically as different from us as possible. The smell contains information about the immune cells of our body. The more significant the difference between two people's immune markers, the higher the likelihood that our offsprings will be endowed with genetic diversity of immune cells and maximum disease resistance.
As soon as we "read" the scent of a particular person, our brain immediately sends us its answer, whether we find it attractive or not. Thus, the smell helps us choose the right partner for healthy offsprings, even if we don't think about it at all.
Even at a distance of two meters, we can perceive the smell of another person. Our sense of smell merely tells us if it is the "right" fragrance for us. As soon as we smell "our" partner, all thoughts turn towards the object of interest.
That is the reason why we get excited in the company of a certain person. That is exactly the situation when love is literally in the air.