#evolutionarybiology

You saw the word yawn just now...and there's a good chance you already felt the urge to do so

but why? you're not tired. nothing changed. someone else's yawn - or even just the idea of one - somehow triggered the same response in your body. that's lowkey weird if you think about it, isn't it?😭

Well, here's what's happening : basically, your brain has a system called mirror neurons ; neurons that fire not just when YOU do something, but when you observe someone else doing it too. Your brain essentially runs a simulation of their experience inside you, in real time and it is the same system that makes you flinch when you see someone fall, or tear up when someone you love cries. You are not just watching them... on a neurological level, you're partially experiencing it with them !

anddd yawning is particularly contagious because it was actually never just about being tired.

the leading theory is that in early human groups, yawning was a synchronisation signal... a way of collectively winding down. A group that slept together was significantly safer than individuals dropping off at different times, leaving the group vulnerable in shifts. Sooo, when one person yawned, the signal spread. It was like your ancestors' way of saying "It's time ! let's rest together."

Have you ever wondered why tigers are BRIGHT orange in colour... even though they hunt in dense green forests?

Aren't they considered to be camouflaging so that their preys don't spot them ?? How is this colour of traffic cones and safety vests - things that you are supposed to spot from far away - helping them "camouflage" in their habitat ??

WELL, Mammals actually cannot produce green fur, it is pretty much biologically impossible. This is because our mammal ancestors spent about a 100 million years, hiding underground at night. And during that time, they lost practically every pigment system. (a classic "use it or lose it" evolutionary process lol) Leaving us behind with only 2 chemicals : One that makes brown and black & one that makes orange and yellow. That is the entire mammalian colour palette. Every dog, horse, lion, deer, even US... All of it is just those 2 pigments mixed in different ratios !

AAAND, the trade off here is... deers cannot tell the difference lol ! They are actually red and green colour blind. Deers have two types of colour receptors , and neither one can separate orange from green. To a deer's visual system, an orange tiger sitting in a green bush , registers as a green bush!

And then there are the stripes...The black markings aren't just aesthetic haha, they break up the tiger's outline in dappled light and tall grass, a phenomenon known as disruptive colouration. So, the orange disappears into green for the deer, and the stripes dissolve the tiger's silhouette in the process.

There's actually a term in evolutionary biology for what tigers are doing. It's called sensory exploitation. Not universal camouflage. Not invisibility to everyone. Just precise, targeted optimisation for the perceptual limitations of one specific audience ;)

As someone whose mind is constantly jumping between memories, worries, ideas and observations... My brain seems permanently committed to keeping at least ten tabs open at once😭, I'm always thinking and thinking - either nostalgic about my past, anxious about my future , or so caught up in my thoughts that I feel like I barely experience the present moment while its happening. And, not living in the present can of course contribute to higher anxiety levels, emotional burnout and fatigue.

So I guess the first step to living more mindfully would be to understand why it is biologically so difficult for us to do so...

Basically, your brain has a system called the default mode network. When you are not focused on a specific task, your brain doesn't go quiet... it activates this network and immediately starts doing what it does best : replaying past events, simulating future scenarios, running social comparisons, imagining things that haven't happened yet. It is your brain's literal default state.

AANDD... It was a huge evolutionary advantage.

The ancestors whose brains constantly rehearsed past mistakes, anticipated future threats and mentally prepared for what came next... they survived. In a world without medicine, without infrastructure, without any safety net whatsoever- replaying the moment you trusted the wrong person, mentally preparing for a predator that might return, or pre-running a difficult social interaction before it happened wasn't rumination. It was critical. Get the social dynamics of your group wrong and you risked exclusion. Miss an environmental threat you'd already encountered once and you might not survive it twice. Fail to anticipate what came next and you were always reacting too late. The ones who simply existed in the present, unbothered and unplanning, often didn't make it. Your brain was never built to rest in the now. It was built to stay one step ahead of what the now might become.

So when you try to just be... no planning, no replaying, no spiralling ; you are fighting hundreds of thousands of years of survival programming. The present moment, evolutionarily, was never really the point ! You are not overthinking because something is wrong with you. You are overthinking because your brain is doing exactly what it evolved to do.

Peter Dazeley//Getty Images Some people flinch at a needle prick faster than others. One possible reason, at least in a very specific experimental setting, may be old very old DNA. In a 2023 paper published in Communications Biology, researchers linked three Neanderthal-derived variants in the gene SCN9A to a lower threshold for one kind of pain test in modern humans: a skin-pricking test…

You are mid conversation and suddenly there's a pause...Nobody speaks. And within seconds it starts to feel genuinely uncomfortable- like something has gone wrong, like you need to fix it immediately...

But why? It's just the absence of sound ?

EXCEPT, your brain doesn't process it that way at all !

For most of human history, silence wasn't neutral. In small social groups, a sudden drop in conversation was a signal : tension, disapproval, exclusion, or an external threat nearby. The individuals who picked up on that signal quickly and responded to it survived social conflicts and dangers at higher rates than those who didn't. So the brain developed a finely tuned sensitivity to conversational silence, treating it not as emptiness but as information.

That sensitivity is still running.

There's a biological mechanism behind this called the anterior cingulate cortex- the part of your brain responsible for detecting social errors and conflicts. Studies have shown it activates during awkward silences the same way it does during explicit social rejection. Your brain isn't just registering that things have gone quiet. It's registering that something is wrong and flagging it as a threat that needs resolving.

This is why the discomfort is so physical. That urge to fill silence, to say literally ANYTHING lol , that's your nervous system trying to defuse a perceived social conflict before it escalates.

And, the awkwardness of silence is remarkably universal across cultures. The threshold varies, but the discomfort doesn't. Research by Dutch psychologist Namkje Koudenburg found that silences as short as four seconds are enough to trigger measurable spikes in feelings of rejection and exclusion in most people.

Four seconds.

BUUUTT, then why does silence feel completely comfortable with people you're close to?

Because the brain isn't just detecting silence, it's reading context. With someone you trust deeply, silence carries no ambiguity. There's no question of disapproval or exclusion because the relationship has already established safety. The anterior cingulate cortex, which fires when silence feels threatening, stays quiet when the social context feels secure.

Psychologists call this "companionable silence".

You know it will scar. You know it will bleed. You know it'll take longer to heal. And yet....

Well, for most of human history, an open wound or parasite on your skin wasn't just annoying, it was potentially fatal. No medicine, no antiseptic, nothing but your own hands. So the individuals who felt a compulsive need to groom, to remove anything foreign or incomplete from their body, survived at higher rates than those who didn't.

and that compulsion never left

There's also something your brain does that makes this worse - a scab feels unfinished. And your brain treats "unfinished" the same way it treats any incomplete task, it nags you until it's resolved. Remove the scab and you'll have a genuine dopamine hit; A small reward for "finishing something"

So you're not being irrational or gross. You're just running grooming software that's been in your biology for millions of years.

Anxiety rates have skyrocketed over the past few decades. The easy answer to that is "all because of social media!" or "just modern pressures" - and yes, those things do play a part BUT... there is a biological story underneath all of that which nobody talks about enough.

So, deep in your brain sits a small almond shaped structure called the amygdala. It's ancient, it's fast, and its entire job is to detect threats and trigger a response before your conscious mind has even registered what is happening. Cortisol and adrenaline flood your system, your heart rate spikes, your muscles tense - you are ready to fight or run within milliseconds. This system is exceptionally good at what it was built for : immediate, physical, short lived danger. A predator. A rival. A fire. You respond , the threat resolves , cortisol drops, and your body returns to baseline.

Notice the emphasis on 'resolves' ?

Well, the problem is that nothing resolves anymore. Modern stressors don't work like predators. Financial stress, social comparison , career uncertainty, climate dread - these threats have no resolution point. There is no moment where your body gets to register "threat gone, stand down." The alarm stays on.

Biologically, chronic stress is deeply novel. Our systems were never designed to run cortisol continuously at low levels for months or years. so when they do, something starts to break down.

Prolonged cortisol exposure is said to physically reshape the brain. The amygdala, your threat detector, becomes more reactive over time- scanning for danger even when none exists. Meanwhile the prefrontal cortex, the part of your brain responsible for rational thought, context, and calming the alarm down, actually shrinks. The brain gets structurally better at being anxious and structurally worse at talking itself out of it.

So you are not imagining that anxiety feels harder to control over time. Your brain has quite literally been physically rewired by it.

Now comes the social media aspect of it... Humans are hardwired for social comparison. In small tribal groups, knowing where you stood relative to others determined your access to food, protection, and mates. Your brain developed a constant, automatic system for benchmarking yourself against the people around you.

That system was built for 150 people you actually knew.

However, social media exposes you to millions! all presenting the most curated, filtered version of their lives. And your brain, running an ancient ranking algorithm it never evolved to switch off, processes every single one as a genuine social comparison. In a real community, hierarchies eventually settle and the anxiety quiets. But the feed is infinite, the comparisons never resolve, and your brain never gets to conclude "I know where I stand." The result is an anxiety with no finish line.