In 1996, Aaron Lynch published Thought Contagions: How Belief Spreads Through Society. The book never achieved mainstream acclaim, and Lynch himself remains a footnote in the history of memetics, overshadowed by Richard Dawkins, who coined the term "meme" two decades earlier. But Lynch offered something Dawkins didn’t: a hard look at the idea that beliefs persist not because they’re true, or helpful, or beautiful, but because they’re effective at replicating.

Contagion, not content, explains much of what survives in the zeitgeist.

Lynch argued that ideas act like viruses, and societies like petri dishes. A belief doesn’t need to make your life better. It doesn’t need to be factually accurate. It just needs to be good at spreading. Some memes do that by promising reward. Others, by threatening punishment. Still others spread by piggybacking on institutions or rituals or trauma. The point is survival through replication, through transmission.

In the years since, the idea has mutated and flourished. It appears in adjacent fields: in Boyd’s cultural evolution models, in the logic of social media algorithms, in memetic warfare theory. It has become obvious that we are not governed by reasoned deliberation alone. Ideas compete.

Some win.

Many don’t.

And the winners are not always the wisest.

Why do some ideas survive? 

We can think in terms of memetic fitness: the ability of an idea to persist across minds, to self-replicate, and to spread with minimal resistance.

Certain traits make memes more fit. Simplicity helps. So does emotional valence. A meme that angers or terrifies you spreads faster than one that calmly explains. Identity congruence is another factor: people are more likely to adopt ideas that reinforce their social group’s worldview. If a thought signals tribal loyalty, it has a higher chance of replication.

And then there’s reproduction strategy. Lynch classified memes by how they encourage spreading: proselytic memes (like evangelical Christianity) demand active conversion; preservational memes (like traditional Judaism) focus on high-fidelity retention across generations. There are also adversative memes, which define themselves in opposition to other ideas. These often thrive in polarized environments.

From this perspective, an idea’s value isn’t measured by truth or usefulness, but by spread rate and persistence. A useful idea might die in obscurity if it’s complex or emotionally neutral. A false idea might flourish if it provokes outrage and confirms bias.

This is unsettling. We like to believe our beliefs are earned. That we believe things because they’re true.

But often, we believe things because they’ve been selected, over time, for psychological stickiness.

The memes got there first.

The internet didn’t invent thought contagion. It merely accelerated it. What used to take decades of cultural transmission can now happen in hours. A tweet, a TikTok, a video clip, a slogan. These are the new vectors of cultural evolution.

Algorithms act as artificial selectors. Twitter doesn’t reward nuanced discussion. It rewards engagement. Instagram etc doesn’t surface the most accurate take. It surfaces the one most likely to generate a reaction. This creates a selection pressure on ideas: evolve to provoke, or die.

Memes that succeed online are those that survive this ruthless environment. They’re short, emotionally resonant, and easily shareable. They often include moral judgment or identity cues. They come with built-in calls to action: Retweet. Cancel. Like. Condemn.

What happens to a society when its dominant ideas are those best adapted to algorithmic selection? We get what we have: ideological monocultures, collective hallucinations, and a population increasingly governed by memetic logic.

There are downstream consequences. When ideological movements prioritize virality, they lose complexity. When political discourse becomes memetic, it loses coherence. And when belief is optimized for transmission, sincerity becomes a liability.

A common critique of memetics: it dehumanizes belief. It makes it seem like ideas control us, rather than the reverse. But that criticism misses the point. Memetics doesn’t deny agency. It reframes it.

We are both hosts and editors. We adopt ideas, but we also mutate them. We remix, reinterpret, retweet. The meme doesn’t just live in us. It evolves through us. Human creativity is still central to the ecosystem - but it operates within the rules of memetic fitness.

Conspiracy theories evolve over time, responding to new events, adapting to skepticism, competing with each other. QAnon didn’t appear fully formed. It built memetic layers through forums, hashtags, media coverage. Each iteration made it more resilient, more engaging, more transmissible.

The people spreading it weren’t passive vessels. They shaped and sharpened it. But they were also influenced by it. They became more conspiratorial, more extreme, more detached from shared reality. The idea infected them even as they fed it.

If we accept that ideas behave like viruses, we have to grapple with the epidemiology of belief. What makes a society vulnerable to memetic disease?

High stress environments are a factor. People under strain are more susceptible to simple explanations. So are atomized societies. When people are disconnected from each other, they’re more likely to seek out identity-reinforcing narratives online. Add in algorithmic targeting, and you get an immune-compromised population.

But we also have to look at mutation rates. The more frequently ideas mutate, the harder it becomes to maintain shared epistemic standards. Truth loses its footing when facts are endlessly reframed and recontextualized. The mind becomes overloaded. And when overloaded, it defaults to heuristics. Which is exactly what memetic viruses exploit.

Contagious thoughts outcompete true thoughts simply because they’re easier.

They require less cognitive labor.

They fit the grooves already carved into our brains.

We can’t fight thought contagion by pretending it doesn’t exist. And we can’t return to some pre-digital ideal where only the best ideas rose to the top. If that world ever existed in the first damned place.

But we can build better filters. Personal ones. Institutional ones. We can teach memetic literacy - help people recognize when they’re being infected by an idea that’s optimized for replication over reflection.

We can also slow down the replication process. Not everything needs to be shared. Not everything needs to go viral. Platforms can play a role here, but so can individuals. A culture of restraint is possible, even online.

And we can try to create high-fitness, high-quality ideas. Ideas that are true and contagious. This is hard. But not impossible. Some thoughts spread because they resonate with deep moral intuitions. Others because they offer clear utility. Others because they’re beautiful.

Our task, if we want to stay sane, is to find and nurture those ideas - to make them contagious without surrendering their integrity.

Ideas are not immune to natural selection.

They compete.

They replicate.

They evolve.

The thought that survives is not always the one we need. It’s quite often, more often than not, the one that spreads fastest. That’s the reality of our memetic environment. But it’s not destiny. Fitness is a function of the environment. If we can change the environment, we can change what survives.

Maybe we can build societies where virality isn’t the highest good. Where coherence, compassion, and clarity are given time to propagate. Where memes evolve not just to capture attention, but to build understanding.

But first, we have to understand the rules of the game we’re in. Lynch did. That’s why Thought Contagions still matters. He didn’t have the final answer. But he asked the right question:

What kind of world do we get, when replication is the highest currency of belief?