Why are we the size we are?

What an odd question. Also, what does it have to do with fiction? For me, at least, it’s important for world building. Right now, I’m creating a huge and detailed world, probably to set stories in later (I posted a map of one tiny section of it before). When making up completely new creatures, it is possible to change things that we think of as fundamental, like having limbs, or a central brain, or only existing in the physical world. Anything we can conceive of, we can create in a fictional world.

For instance, in my world there are intelligent creatures several inches high and other 350 feet high. I don’t have to explain how that’s possible, since it’s just fiction, but that got me thinking: why are we the size we are? Could we be just like we are now, except the size of ants, or the size of mountains? Here are my thoughts on the subject.

Why it would be harder to be bigger

Being a little bigger is not that hard. Elephants are pretty big, although compared to the tallest living thing on earth, a 380-foot redwood, they’re tiny. Trees have it easier though, since they have a rigid cell structure, they go straight up, and they don’t move. But could we ever be that tall? One problem is the weight. We would need to have incredibly strong bones to hold ourselves up if we weighed 100 tons or so. A couple ways around this would be to be mostly gaseous, like balloon people, to live on a smaller planet with less gravity or have bodies built of some insanely strong material, like titanium-alloy lattice or something.

Another problem with being very large is the time it would takes nerve signals to travel to the extremities. From what I have found (correct me if I’m wrong), nerve impulses travel about 100 meters, or 330 feet per second. So, if we were 350 feet tall and stepped on a nail, it would take a whole second for us to realize it. That’s kind of hard thing to live with, always being one step behind the rest of your body. This could be overcome possibly by having some other way of sending nerve impulses or to have a diffused brain, or even several brains that could handle various parts of the body. In any case, we would have to be radically different in design if we were going to be super huge.

Why it would be harder to be smaller

If only we could ride ants and sleep in a Lego block

Well, how about being smaller? Could we be the size of ants and still be just as intelligent as we are now? The problem with being smaller is that we would have smaller brains. Perhaps if our brains worked differently, they could be much smaller, but as things are now, there is a reason why we are so much smarter than insects.

Another issues about getting very small is the loss of resolution. It’s like if you zoom in on a picture; at some point it will start to pixelate, because as the size of the whole picture gets closer to the size of the pixels, it is harder to show detail.

One of my favorite mugs.

In the picture above, the number of pixels is huge, so even after zooming in three times, you can only just begin to see them. For living things, the things we are made of–atoms–are insanely small, so we would have to be pretty small before we started to lose complexity, but the point is, that we could not be just any size and still be intelligent human beings. Look at what a car looks like when it’s made of individual atoms, compared to a real car.

The molecular car image courtesy of Wired.

Yeah, there’s no comparison, in terms of complexity. In the same way, we could not be very tiny and still be us. At what size that loss of complexity would start, I’m not sure. If you have any idea, let me know.

So…that’s what I think about all day. I’m not an expert on this sort of thing; I just like to think about it. If you have any thoughts, please share them in the comments.