Why mapping perception is not the same as proving reality is fake. #
Posted June 20, 2026 [ Reviewed by Jessica Schrader
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Key points
- Mapping a fruit fly brain shows mind complexity scales with connections, not neuron count.
- Human brains have synaptic connections equivalent to 10 million flies.
- The drive to "know" reality reflects psychological needs more than objective evidence.
Like the lunar landing, the mapping of the familiar fruit fly in 2024—bane of humid groceries and kitchen cringe—represents a major accomplishment. Other creatures have been mapped, but Mr. Fly is so iconic, now living within a simplified computer simulation since March of 2026... unaware it is not real. After years of work and the kind of machine learning that can trace a single circuit through a fog of tissue, researchers completed the first full wiring diagram of a fruit fly brain—139,255 neurons, some 50 million connections between them.
The fly's 139,000 neurons stand against our 86 billion, yet the gap is one of scale, not of kind. If a fly can be mapped, so—by a sufficiently advanced system—can a human. It's a tall order, but conceivable, particularly with the kind of technological advances AI might soon catalyze.
Mapping Me? #
Tell someone their mind could be mapped and the next thought tends to arrive unbidden: that maybe none of this is real, that we are already inside someone else's simulation, the way Mr. Fly is inside ours.
The reach is understandable—I love the idea of reality glitching as much as anyone—but why suppose in the first place reality is a simulation when we can chalk up what we experience to the properties of the human brain? There is no way to prove, or disprove, the simulation hypothesis, any more than the familiar unfalsifiable flying spaghetti monster. Consider what the hypothesis assumes: if the simulation hypothesis is true, then there is something beyond the simulation which is "real." It does not abolish reality; it relocates it one floor up and leaves open infinite possibilities for iteration. That a mind can be mapped, even run, cannot be validly used to support the simulation hypothesis of reality. What remains is essentially a faith-based system, driven more, as I see it, by an individual's psychology and feelings about themselves and the world than anything objective. Wishful thinking, perhaps. But wishing for what? The mask of objectivity is just bluster, human beings unable to fully recognize our own limitations. We make up stories to get us through the day, but when reality comes knocking we are often at a loss for words.
Readers may be familiar with circumstances when they were surprised by something they were so sure about, often in positive—but sometimes in quite unfortunate—ways.
Humble Pie #
The significance for the human condition is a useful humility about just how complex we are. The fly's neurons cost a global effort and years of machine attention; we carry 86 billion, and what they do is harder to set down than the wiring that does it—the brain ingests reality and produces new reality, in a limited scope, to use the word reality loosely, given our dim grasp of the situation. A connectome is a snapshot of the machinery; the thing itself is an engine for making reality we have only begun to understand.
Neuronal number doesn't do the situation justice, however. By neuron count, you are roughly 620,000 fruit flies. Chill that many into stillness and they'd fill about a 2-litre bottle—a small bucket. That bucket holds every neuron your skull does. Pour it out, though, and it is just flies, and also they'd take up more space once they warm up buzzing again. The count doesn't count.
A mind is what the neurons are wired into, and by the measure that actually matters—connections, not cells—and you'd need a much bigger bucket. Counting synapses—the connections among neurons, which are roughly compared to the number of parameters of a frontier AI model—you are nearer 10 million flies than half a million. To fuse that swarm into a single mind rather than a heap of insects, every fly would have to sprout new connections to all the others—somewhere between 100 million and well over 1 billion apiece, more than a fly could lift. The neurons are in a way the easy part, the solid part. The connections—what might somehow transform a swarm into a someone—are as gossamer as the fruit flies' delicate wings.
Vertigo and Ground #
There is a second shift, harder to hold. We can make simulations and be outside of them—as with the fruit fly—and that is a significant perspective shift. For now, we are on the outside. It is a step closer to the brain-in-a-vat situation, where we do upload human minds and they may or may not know they are uploads. If I am an upload, I am not aware of it—but I'd want to know. Would you? What if I am just a swarm of flies, and not a simulation? Is that another flying spaghetti monster, more absurd perhaps, more disturbing undoubtedly.
Either way, wanting to know is a choice—and we make choices, and they have consequences. The one part of us the connectome cannot hold is the one that matters most here: that if we pay attention to what is going on inside of our own psyches, we get crucial information—both about ourselves and the outside world, and the better we are at this, the earlier we become aware of time-sensitive information, windows of opportunity, and long-term chains of events which lead us where we want to be—to who we want to be. That is how we live in "the best of all possible worlds." That's the little bit of influence some philosophers think we might have — exactly where paying attention does the most to transform raw experience into usable thinking.