How would the human body function at reduced sizes?

[Marr]

I'm a cartoonist and I'm currently working on a story that involves a 6-inch person and a long, outdoor trek. I'd like to introduce as many real-world issues to the equation as possible, and so here I am, intruding upon your forum to pick your mighty brains. :)

I'd really be interested in any insights you might have. Anything from metabolism to jumping distance and sturdiness of frame, etc., etc.

I do have a specific question to start your gears turning, though: would the sense of smell behave the same way? By that I mean, would pumpkin pie still smell like pumpkin pie, or would it smell different?

 

[EnumaElish]

Can you describe the exact (even approximate) mechanism, process, or transformation through which the reduction takes place? I am not asking for a "plausible" story, only a specific one among many possible. For example, does a reduced human (mini sapiens?) weigh as much as a normal one? The answer to this depends on how exactly the reduction occurs. Are there fewer atoms or molecules per unit volume in the mini sapiens body, or are their atoms and molecules themselves being reduced in size? A mini sapiens will weigh less than a homo sapiens in the the former case but not in the latter case.

 

[Marr]

Can you describe the exact (even approximate) mechanism, process, or transformation through which the reduction takes place? I am not asking for a "plausible" story, only a specific one among many possible. For example, does a reduced human (mini sapiens?) weigh as much as a normal one? The answer to this depends on how exactly the reduction occurs. Are there fewer atoms or molecules per unit volume in the mini sapiens body, or are their atoms and molecules themselves being reduced in size? A mini sapiens will weigh less than a homo sapiens in the the former case but not in the latter case.

Hmm- good point. Well, this would be a regular human being who has been reduced, much like the main character in the Incredible Shrinking Man. However, it's been established previously in the storyline that the person's weight has been reduced in proportion to his size. So this fellow weighs about what you would expect a normal 6-inch critter to weigh.

 

[EnumaElish]

One obvious question that I don't know the answer for is: with a brain much smaller than that of the human, would the miniman be any stupider than his bigger counterpart? Put another way, will his intelligence be closer to a man's than to a spider monkey's, assuming a discernible difference exists between the two in the first place? Let's hope that a browsing biologist will become bored and attempt to answer this question.

I'll venture to guess that the miniman's sense of smell might be somewhat weaker in the overall: with a reduced body surface area, he will have fewer nerve ends available to detect adrift molecules from a pumpkin pie or a pile of poop. If this reasoning is not altogether laughable, then the same has to be true for other senses as well.

His smaller brain might compound this effect because of his lower "CPU power" available to process all the sensory inputs.

 

[hypnagogue]

A lot depends on what you conceive of happening to his brain. If you imagine his brain has the same number of neurons and number of connections as an average human, the intelligence could plausibly be the same as well. But if he doesn't have mini-neurons to make this possible (I guess neurons reduced in size by a factor of about 12), then there's no way he'd have the same intelligence and overall range of cognitive capacities as a normal human. Of course, having such mini-neurons might change the way his brain functions anyway (neurons would be closer together so there might be more crosstalk or other strange or unpredictable effects, and also action potentials could propagate across neural networks faster), but I think you could overlook that.

 

[EnumaElish]

Thanks, hypnagogue. Your not having posted any icons has made me somewhat more hopeful that my theory about fewer nerve ends may not have been altogether on the same level with a Jon Stewart joke. However, if your professional ethics compels you to dash my hopes, will you at least be gentle?

 

[Moonbear]

Weeeeeelllll...we could think about the way small mammals function, which is different than humans. Their brains lack a lot of the cortical development that humans have, so while they have very well developed olfactory bulbs (relative to the size of the rest of the brain, they're huge) and have excellent senses of smell (better than humans), they don't have the structures that would suggest they are capable of higher thinking.

The blunt answer is that a 6 inch human couldn't function as a human. But, it's a cartoon human, not a real human.

Some things we could predict are that with the change in size, the surface area to volume ratio of his body would be increased, so he'd lose heat more rapidly and would need to eat more in proportion to his body size to maintain body temperature. Bones would be incredibly fragile if shrunken proportionally, so broken bones would likely result. Small mammals usually have much faster rates of heartbeats, so that's another thing your fictitious character might experience.

You might want to consider how he perceives the world around him. Does he still see that slice of pumpkin pie as a normal sized slice by comparison with its surroundings but then can only eat a few nibbles before his tiny stomach is full, or does it appear to him as monstrous because it is so much bigger than him?

 

[EnumaElish]

Bones would be incredibly fragile if shrunken proportionally, so broken bones would likely result.

If this is so why aren't small animals' bones shattering like glass?

 

[Moonbear]

If this is so why aren't small animals' bones shattering like glass?

They are pretty fragile too (meaning thin, so easy to snap or crush, not shattering type fractures). But, part of my reasoning, without doing any calculations on it, is that if you scaled a human down proportionally to only 6 inches tall, your bones would be even skinnier than in a small animal of that size. I could be wrong on that.

 

[TRCSF]

Getting wet would be a problem. As would be getting in and out of water.

I don't think smell would be as significantly changed as other.

 

[EnumaElish]

Getting wet would be a problem. As would be getting in and out of water.

Why and why?

I don't think smell would be as significantly changed as other.

Other what?

 

[scrappychic]

I wouldn't think that smell would be affected because, my understanding is that molecules of the food you smell attach to sensors which sends a signal to the brain. Since molecules are so small, you would still get a very large number of molecular scent signals being sent to the brain. Another reason I think smell would be the same is that there are other small animals that have an excellent ability to detect odors. If your imaginary person was the size of a molecule, then that would be different.

 

[Evo]

If this is so why aren't small animals' bones shattering like glass?

Think of a cat falling from three times it's height and think of a human falling from three times their height. We're made differently. A cat getting knocked off a kitchen table will cause no harm, while a tiny human getting knocked off from that height would probably be fatal.

Dogs have an incredibly keen sense of smell, but they (mostly) are much smaller than humans. But considering the height of the tiny person, they may be experiencing different smells. A normal size human might be savoring the smell of a roast turkey coming out of the oven, while the tiny human closer to the floor might be smelling less savory dirt and debris at his level.

A flee can jump what is equivalent to an entire football field, no tiny human could do that. Many insects can effortlessly pick up many times their weight. A tiny human would be at a great disadvantage.

 

[Marr]

Thanks for all the input, people. I do wonder- would the bones be more fragile at that size or more sturdy? Seems like a human skeleton would be almost over-engineered at that size. For a more extreme example, an elephant skeleton seems awfully robust compared to a mouse skeleton.

I mean- if you could shrink an elephant down to the size of a mouse, wouldn't it be much sturdier than a mouse? Wouldn't it be engineered to withstand (proportionally speaking) much greater amounts of weight? Or for a reverse example, if you could make an ant the size of an elephant, wouldn't it be unable to stand? Or if it did, wouldn't it's legs break?

 

[Intuitive]

I think the complexity of the brain is what makes intelligence, not the size, sperm whales have much bigger brains than we do and we are much more complex in our thought process than they are, otherwise they would be the dominate species and rule the world like we do, We have the brain power right now to cause (all life) to become extinct, Sperm whales do not.

 

[EnumaElish]

We have the brain power right now to cause (all life) to become extinct, Sperm whales do not.

Some brain power. And interesting example.

 

[hypnagogue]

I think the complexity of the brain is what makes intelligence, not the size, sperm whales have much bigger brains than we do and we are much more complex in our thought process than they are, otherwise they would be the dominate species and rule the world like we do, We have the brain power right now to cause (all life) to become extinct, Sperm whales do not.

Much of the sperm whale's larger brain is dedicated to taking more sensory information in from, and sending more motor signals out to, its much larger body. As regards brain size, what is important is not so much absolute measurements but measurements relative to body size.

In any case, you're right that larger brain size does not guarantee more high-level cognitive processing-- it depends on how those neurons are actually wired together and what they're actually doing. Nonetheless, it's also true that some appreciable brain size (number of neurons) is needed to implement more complicated neural algorithms over some reasonable time scale. The loss of processing power that a miniscule human-like organism would suffer would most likely prevent it from having cognitive capacities anywhere close to a human, no matter how cleverly (or complexly if you prefer) those limited number of neurons are arranged.