Today I’m going to talk about something that sounds almost impossible: scientists have mapped the brain of a fruit fly so precisely that people can now build computer simulations based on its neural connections. A fruit fly has roughly 140,000 neurons in its brain, which sounds tiny compared with a human brain, but when you actually try to map every neuron and millions of connections between them, it becomes unbelievably complicated. Researchers have now created something called a connectome, basically a wiring diagram showing how the neurons in a fruit fly brain connect to one another.
And recently, people started doing something even stranger with this information. They took these fruit fly brain models and connected them to computer environments. Some programmers have experimented with making simulated fruit fly neural networks interact with games such as Doom, Super Mario 64, and Beat Saber. Now, I want to be very clear: this does not mean someone uploaded a living fruit fly brain into a computer. It is still a mathematical simulation based on the wiring of a real brain. But even knowing that, I still think it is incredibly weird.
Because here is my question: if you simulate enough of a brain, when does it stop being just a simulation?
At first, the answer seems obvious. It is just software. There is no real fly sitting inside the computer thinking, “I really want to play Doom today.” The neurons are mathematical models, and scientists decide how information enters the system and how its outputs control something on a screen. But then you start thinking about it more deeply. The wiring itself came from a biological brain. The connections were not invented by an AI engineer. They were copied from an actual animal.
So what exactly are we looking at?
I think this is where the idea becomes much more interesting than simply saying, “Look, a fruit fly can play a video game.” The real question is what a brain actually needs in order to produce behavior. If you reproduce its connections and simulate electrical activity moving through those connections, can some behaviors appear naturally? And if they do, what does that tell us about intelligence?
One important thing is that this is not the same thing as normal artificial intelligence. Systems like ChatGPT are artificial neural networks designed by humans and trained using enormous amounts of data. A fruit fly brain simulation is trying to model the structure of an actual biological nervous system. That does not automatically make it alive, and it definitely does not mean it is conscious, but the starting point is very different.
And consciousness is where everything becomes confusing.
How would we even know if something inside a computer were conscious? We cannot directly measure consciousness even in another human being. We assume other people are conscious because they behave like us, communicate with us, and have brains similar to ours. But what happens when you have a simulated brain? If it reacts to something, learns something, or changes its behavior, does that mean it is thinking? Probably not necessarily. But where exactly is the line?
Right now, fruit fly brain simulations are still extremely limited. Mapping the connections is already incredibly difficult, but a wiring diagram is not the same thing as understanding everything happening inside a brain. Real neurons involve chemistry, electrical signals, hormones, molecules, changes in synapses, and probably many things we still do not fully understand. A computer model simplifies a lot of that. So even if you have every connection mapped perfectly, you still might not have the complete brain.
That is also why going from a fruit fly to a human brain is not just a matter of making the computer a little bigger. A human brain has around 86 billion neurons. The jump in complexity is enormous. We are nowhere close to creating a complete working simulation of a human brain.
But that does not make the fruit fly experiment unimportant. Actually, I think it makes it even more interesting. We are starting with one of the smallest complicated brains we can study, and even that is incredibly difficult. If we can eventually understand how behavior emerges from those tiny networks, maybe we can slowly understand bigger brains.
There are also risks. Whenever humans develop a technology that can imitate biological intelligence, we should probably ask what happens before we make it much more powerful. What if one day simulated nervous systems can learn far more complicated tasks? What if we eventually build models based on mammals? And someday, maybe humans? At what point would we have to start thinking about whether a simulation deserves some kind of ethical consideration?
I do not think anybody knows the answer yet.
And that might be the most interesting part of the entire story. We are learning how to simulate parts of biological brains before we completely understand what consciousness actually is. We are building models of something that we still cannot fully explain.
And then there is one final question that makes everything even stranger.
If someday we can simulate a brain so accurately that the simulated brain cannot tell the difference between its world and reality, how would we know that our own brains are not inside some kind of simulation too?
I definitely do not have an answer to that.
But maybe that is exactly why studying something as tiny as a fruit fly brain can lead to some very big questions.
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