Homunculus

Homunculus is something like a retro-Latin word. The base word homo means human, but the added suffix at the end makes it into a diminutive form.

Basically, you’re describing a little human being, like a micro-sized version of you.

The term was put together centuries after the fall of Rome, long after Latin was in common use in Europe. An alchemist named Paracelsus working in Switzerland used the term in print in De Natura Rerum, published after his death in 1572.

Here, he described how to make a little person by using alchemy. This process is interesting enough for me to carve out some space here. Reasoning that a human incubates inside of a mother for several months, Paracelsus had the idea to place human sperm in a sealed flask.

Then, things get kind of weird. Okay, they get kind of weirder.

Paracelsus suggested burying the flask in a big pile of horse poop. No, this isn’t just an excuse for me to write about poop (this time), but instead, Paracelsus was obsessed with the properties of dung. Maybe he noticed some insects crawling around in some horse poop and concluded that it was a fertile place for life, but the idea was certainly also to generate warmth to mimic human gestation.

After 40 days, you were supposed to open up the flask to find not a baby, but instead a miniaturized, fully formed human in there, which you were then to feed human blood.

Now, that’s pretty weird, but it’s not our last visit with semen for today. Sorry!

With the advent of microscopes, we started seeing fewer alchemical theories based on grasping at observational straws. Still, there was plenty of unknown wonder scientists could now see, and what they saw demanded answers.

When they looked at semen, they saw sperm swimming around in there. Now, you have probably seen video of sperm under a microscope, and they look a lot more like wiggly tadpoles than little humans.

Unfortunately for scientists working in the 1700s, the resolution was very, very limited. So was the magnification. Glass was pretty much always a little bit imperfect, so the lens would distort the image on the other side as well.

TL;DR: people took the homunculus and ran with it. They believed that they were seeing fully formed little humans here, and the idea that organisms developed from miniature versions of themselves was prominent at the time. Couple this with a little confirmation bias and you clearly have a miniature human here.

Of course, there’s also pareidolia, our tendency to see patterns—especially human-shaped patterns—in just about everything—even dancing tadpoles under very low resolution.

There’s one more homunculus I want to share with you today. Thankfully, this one has nothing to do with sperm or poop. This is all about the little person who lives inside all of us.

I’m talking about the motor cortex map. This is a real tiny person who lives inside each of us. A part of our brain called the primary motor cortex is responsible for moving your limbs around. It’s not just your limbs, either: pretty much anything you can wiggle or move on your body voluntarily is controlled here.

How does it work, you might ask? Well, there’s a kind of “map” inside that matches up with your body on the outside. This is a bit like having a puppeteer inside of us, where a distorted version of our bodies is moved around, causing the real body parts to move in sympathy.

It’s important to keep in mind that the map is not the territory. The sizes of each region in the map don’t match up with physical size in the outside world, so you don’t actually have a true miniaturized human-shaped form living inside of your brain. Instead, the regions are bigger wherever there’s a lot of precise skill and precision needed.

Hands, face, and mouth all have huge representations on our motor cortex maps. By contrast, your legs, arms, and torso take up little space. You end up with a wildly distorted homunculus—just a strange little model of you existing inside your physical brain space.

So, there’s the actual homunculus who lives inside of us, operating like a puppeteer for our voluntary movements. Then, there’s the fantastical theories from centuries past that made use of the same idea, of a miniaturized, fully-formed human being responsible for reproduction.

Which homunculus speaks to you today?