It's one of those questions that arrive without warning, usually late at night or during a long stretch of highway. What if everyone else disappeared? Not in a dramatic, cinematic way no explosions, no zombies. Just... gone. You wake up tomorrow and you're the only one left.
Most of us treat this as an idle thought experiment. We mentally inventory the supermarkets we'd raid, the mansions we'd explore, and/or the dogs we'd adopt. Oh, the dogs we’d have…
But psychologists and neuroscientists have spent decades studying what actually happens to the human mind when it's cut off from other people and the answer is far stranger and more revealing than any post-apocalyptic fantasy suggests.
The truth is the question isn't really about survival. It's about what we are without each other.
The First Hours: Freedom and Its Disconnect
In every thought experiment and every fictional treatment of the "last person" scenario, there's an initial phase that feels almost euphoric. No obligations. No judgment. No rush-hour traffic or awkward small talk. The entire world is yours.
This tracks with what psychologists know about voluntary solitude. Research by Thuy-vy Nguyen at Durham University's Solitude Lab has shown that short periods of time alone — 15 to 30 minutes — reliably produce a calming effect, reducing both positive and negative high-arousal emotions. In small doses, being alone dampens the noise. It's why retreats work. It's why closing your office door feels like relief.
But the operative phrase is small doses. Nguyen's research and related studies have found a critical threshold: once isolation extends beyond roughly 10 hours with no social interaction at all, the effects begin to shift. Energy drops. Cravings for social contact intensify. The calm starts to feel less like peace and more like something missing. Suddenly, you miss the persistent phone calls from your mother. You’d actually pick up if she’d call now.
For the last person on Earth, the euphoria of unlimited freedom would likely curdle within days, not weeks. Because the irony is that freedom with no one to share it with is just another word for emptiness.
The Social Brain Problem
Here's the uncomfortable truth that neuroscience keeps confirming: the human brain did not evolve to function in isolation. We are, at the most fundamental neurological level, social animals. Our brains developed in the context of group living, and a staggering amount of our cognitive architecture is dedicated to understanding, predicting, and communicating with other people.
John Cacioppo, the late University of Chicago neuroscientist who pioneered the study of loneliness, proposed an Evolutionary Theory of Loneliness that frames the feeling not as a weakness but as a biological alarm system. Just as physical pain signals tissue damage, loneliness signals social disconnection—and triggers a cascade of physiological responses designed to push us back toward the group.
The old evolutionary pull.
Me stay with group so me don’t get eaten by saber-toothed tiger.
In the short term, this is adaptive, almost good for us. Loneliness makes you vigilant, alert to social opportunities, and refreshed/motivated to reconnect. But when the alarm can't be turned off—when there is literally no one to reconnect with—the system becomes destructive. Chronic loneliness is associated with elevated cortisol (the stress hormone), increased inflammation, disrupted sleep architecture, suppressed immune function, and accelerated cognitive decline.
The last person on Earth wouldn't just feel lonely. Their biology would begin to work against them in measurable, physical ways. The body would respond to permanent social isolation as a state of ongoing emergency, burning through resources to solve a problem that has no solution.
The Ontological Crisis: Am I Still Real?
Perhaps the most unsettling psychological consequence of total isolation is one that sounds almost philosophical but has been documented in clinical settings. Researchers studying the effects of extreme solitude—in prisoners held in solitary confinement, in polar expedition teams isolated for months, in sensory deprivation experiments—have noted a recurring phenomenon: people begin to question whether they, or their surroundings, are real.
Psychologists call this "ontological insecurity." Without other people to mirror our experiences, confirm our perceptions, and validate our existence through interaction, the sense of self destabilizes. We are, more than we realize, constructed through relationships. We know who we are partly because other people reflect us back to ourselves—through conversation, through reaction, through the simple act of being seen.
Remove all of that, and identity starts to blur. Accounts from people who have endured extreme isolation frequently describe a creeping uncertainty: Am I really here? Did that just happen, or did I imagine it? Whose voice is that in my head? The boundaries between thought and perception, between memory and reality, between self and environment, begin to soften in ways that can be profoundly disorienting. For the last person on Earth, the question "am I still me?" would eventually become not philosophical but urgent.
The Impulse to Record
There's a fascinating pattern in accounts of extreme isolation, whether real or fictional: the isolated person almost always begins to document. Robinson Crusoe kept a journal. Antarctic explorers wrote obsessively in their diaries. Prisoners in solitary confinement scratch marks on walls, compose letters to no one, and whisper stories to themselves. The impulse isn't practical—no one is coming to read these records. It's psychological. It's a way of insisting, against mounting evidence, that your experience matters.
Why do you think Chuck Noland befriended a volleyball?
This impulse makes deep psychological sense. Writing—recording, narrating, organizing experience into language—serves as a substitute for the social validation that isolation removes. When you describe what happened to you today, you create an implied audience. You structure experience into a coherent narrative, which stabilizes the sense of self that isolation erodes. The act of recording is, in a very real sense, an act of psychological self-preservation.
This is precisely the premise of The Last Book: The Diary of the Last Earthling, an illustrated book by Hungry Minds that imagines what the very last surviving human would choose to record. The character, Noah Kaplan, escapes the destruction of Earth aboard a mysterious alien spacecraft and begins documenting everything he can remember about humanity—its culture, its achievements, its absurdities, its beauty. Part encyclopedia, part diary, part love letter to a species that no longer exists.
What makes The Last Book psychologically resonant isn't the science fiction premise. It's the recognition that Noah's impulse—to record, to preserve, to insist that all of this meant something—is exactly what a real person in that situation would do. It's the most human response to the most inhuman circumstance: faced with the end of everything, you pick up a pen and start writing.
What We Owe Each Other (Literally)
Anthropologists have long noted that every human culture that has ever been documented, without exception, has developed elaborate systems for maintaining social bonds. Language, storytelling, music, ritual, gift-giving, shared meals, games—these aren't luxuries or decorations layered on top of "real" survival needs. They are, in a very concrete neurological sense, survival needs themselves.
Social neuroscientist Matthew Lieberman's research at UCLA has demonstrated that the brain processes social pain—rejection, isolation, exclusion—using many of the same neural circuits that process physical pain. Being left out doesn't just feel like it hurts; it literally can. In terms of brain activity, it does hurt, activating the dorsal anterior cingulate cortex and anterior insula in patterns remarkably similar to those triggered by physical injury.
This isn't a design flaw. It's a feature. Evolution made social disconnection painful because, for most of human history, being separated from the group was genuinely life-threatening. The lone human on the savanna was the one who got eaten. Our nervous systems still carry that math, even in a world where isolation is rarely physically dangerous—and even in a thought experiment where the danger has been entirely removed.
The "last person on Earth" scenario strips away every social structure simultaneously and asks: what's left? The answer, if the psychology is any guide, is a creature in crisis—not because of any external threat, but because the thing it most needs to function has been removed.
Solitude vs. Loneliness: The Critical Distinction
There is, it should be said, an important difference between solitude and loneliness—and collapsing them is a mistake that popular discussions of this topic frequently make.
Solitude is the state of being alone. It can be chosen, temporary, and profoundly restorative. Writers, artists, meditators, and anyone who has ever needed to think clearly knows the value of deliberate solitude. Research consistently shows that chosen, time-limited solitude can reduce stress, increase self-awareness, and support creative thinking.
Loneliness is different. Loneliness is the distress that arises when the gap between the social connection you want and the social connection you have becomes painful. It's a subjective experience—you can feel lonely in a crowded room and content in an empty house. What defines loneliness isn't the absence of people but the absence of connection.
The last person on Earth would experience something beyond both categories. Not solitude, because it's not chosen, and it's not temporary. Not loneliness in an ordinary sense, because loneliness implies a gap that could theoretically be closed. What they'd experience is closer to what psychologist Robert Weiss called "emotional isolation" at its absolute extreme—the permanent and irrevocable absence of any possibility of human connection.
We don't have a good word for that, which is perhaps why the scenario haunts us. It describes a condition at the edge of language. Mainly because that circumstance hasn’t ever happened before.
Why We Keep Asking the Question
The "last person on Earth" thought experiment has persisted for centuries—from Mary Shelley's The Last Man in 1826 to countless films, novels, video games, and late-night conversations—because it's not really about the end of the world. It's about the value of other people. By imagining their total absence, we're forced to confront how much of what we call "self" is actually built from relationships, from shared experience, from the simple fact of being known.
The psychological research confirms what the thought experiment implies: we are social creatures to our core, and the structures of connection we've built—language, art, culture, community—aren't just nice to have. They're the architecture of consciousness itself.
The Last Book takes this question and transforms it into something beautiful. Noah Kaplan, drifting through space with no one to talk to, does the one thing that keeps a person tethered to their own humanity: he remembers. He records. He bears witness. His encyclopedia of human civilization isn't a survival guide—it's an act of love for a species that no longer exists.
And in doing so, he reminds us of something easy to forget when we're surrounded by people: the most extraordinary thing about being human isn't what we can do alone. It's what we become together.
Want to explore the question further? The Last Book: The Diary of the Last Earthling arrives later this year. And if you're curious about what humanity would need to rebuild from scratch, start with The Book: The Ultimate Guide to Rebuilding Civilization.
Hungry Minds is an independent publishing house and creative studio building a world of ideas designed to feed the hungry mind in us all. Explore our full collection of books, puzzles, and curiosities.
