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On the Biophysics of Hobbits

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kassyopeia from terrae nullius Since: Nov, 2010
#1: Dec 12th 2010 at 6:24:04 PM

Cool title, huh? cool

It occurred to me that, in an Earth-like fantasy setting, there are many advantages to shrinking humans (in the sense of the humanoid species to which the protagonists belong, whatever it may be called) to half our size. Keeping the proportions intact (if you think this is a bad assumption, feel free to argue), such people would weigh 5-10 kg.

What advantages, you ask? Well, for one thing, it makes it a lot more plausible (physically speaking, not evolutionarily) to have a winged sub-species capable of flight, since e.g. large eagles do indeed fall into this weight range. Along similar lines, these people's mounts could weigh as little as 50-100 kg (10% is commonly taken as an acceptable load for a large animal to carry on its back for extended periods without too much strain; horses, with up to 20%, are an exception), which means interesting species like wolves, lions and ostriches, to name just a few.

Before someone objects, yes, there were 75-kg birds and 750-kg predators once upon a time, so doing this with normal-sized humans is not impossible. But we know far less about their behaviour, and they were certainly a lot more ponderous than modern animals, so I find that approach less appealing.

Also, it makes the world a lot more hazardous (always welcome). A normal human with a spear (and the skill to use it) pretty much takes the apex spot in any terrestrial ecosystem. Shrink him, and the predators look a lot more intimidating. Now, all the man-against-nature stuff writers loved to tell tall tales of in the good old days becomes entirely realistic: Eagles CAN snatch children. Crocodiles and pythons CAN swallow adults whole. A cave bear is REALLY bad news. Yay!

So, I hope I've made my case. What I want to know about is in how far I need to take a diminished physiology into account when writing action sequences.

What seems obvious is that they would be better jumpers and climbers and less likely to sustain injuries from falls (all distances reckoned in terms of body size). This should be so because they are stronger, relative to their own weight - and if you've ever observed a beginners' class in rock climbing for children, you'll know exactly what I mean. Surely, there's more, though...

ETA: Oh, I just thought of an entirely different aspect: They'd only need 1/8th the amount of food we need, so a given area can support 8 times as many people. That, however, would be perceived as a doubling of population density, since this is an areal, not a spatial, measure. I wonder if this is too simplistic, or if it really works like that in the natural world? There are many examples that would seem to support this idea, but a few, like Wildebeest herds, that don't fit at all.

edited 12th Dec '10 7:12:33 PM by kassyopeia

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.
GiantSpaceChinchilla Since: Oct, 2009
#2: Dec 12th 2010 at 8:38:17 PM

I kind of doubt your hobbits would be all that athletic, the square cubed law only covers so much ground and thier reduced mass would be able to exert one twenty fifth of the energy of hobbit of human size if memory serves.

kassyopeia from terrae nullius Since: Nov, 2010
#3: Dec 12th 2010 at 8:52:42 PM

The way I understand it, the square-cube-law relates changes in strength (related to muscle cross-section, thus "square") to changes in weight (related to volume, thus "cube"). That would suggest the hobbits would be relatively twice as strong, and consequently indeed more athletic.

When it comes to energy, you're probably onto something. They wouldn't be able to exert their full strength as long as we can, because reserves have to scale down with volume. Good point!

edited 12th Dec '10 8:55:46 PM by kassyopeia

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.
GiantSpaceChinchilla Since: Oct, 2009
#4: Dec 12th 2010 at 9:01:27 PM

to elaborate by square-cube-law I was referring to the strength of the bones to withstand stress not the muscles, reasoning something that small would not have a significantly greater advantage in that area. Then again I am just going on memory here.

Edit: Emphasis added for T-rex vrs mouse debate.

edited 12th Dec '10 9:28:49 PM by GiantSpaceChinchilla

kassyopeia from terrae nullius Since: Nov, 2010
#5: Dec 12th 2010 at 9:14:30 PM

Well, all the advantages are relative advantages, or course. Absolutely speaking, a thinner bone is of course more fragile.

To illustrate, consider a mouse and a T-Rex. I can crush the mouse under my foot, but not the T-Rex, because it is absolutely more robust. Then again, if the T-Rex trips while running, it's likely to break its neck, which could never happen to a mouse, because it is relatively more robust.

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.
GiantSpaceChinchilla Since: Oct, 2009
#6: Dec 12th 2010 at 10:20:44 PM

T-rex vrs mouse debate, just realized it sounds like a fight to the death [lol]

doorhandle Since: Oct, 2010
#7: Dec 12th 2010 at 10:40:28 PM

I'd like to see the fight, but it's a little uneven. Maybe Three Hundred T-rexes vs a SEA of mice...

kassyopeia from terrae nullius Since: Nov, 2010
#8: Dec 13th 2010 at 1:46:40 AM

Well, let's just make it a fair fight. 10 metric tons of T-Rex versus 10 metric tons of mice.

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.
LoniJay from Australia Since: Dec, 2009 Relationship Status: Pining for the fjords
#9: Dec 13th 2010 at 2:12:19 AM

... wierd, this syncs up with some of the world building I've been doing.

Another thing to note, as you get smaller, is body heat. Your hobbits will have a larger surface area for their volume and so will lose heat fast. I'm not sure whether the difference will be big enough to be noticeable, though.

The thing about mounts - the trouble with riding things like wolves and big cats is that their back bends much more when they run than a horse's does. The spine of the horse is very rigid, and I think that's the reason they're a safe and practical mount. A big cat would be very uncomfortable to ride, and I'm not sure how you'd fit a saddle to them.

edited 13th Dec '10 2:13:14 AM by LoniJay

Be not afraid...
MattII Since: Sep, 2009
#10: Dec 13th 2010 at 2:16:40 AM

How smart are they, I mean their brain is only 1/8 the size of ours right?

edited 13th Dec '10 2:16:59 AM by MattII

kassyopeia from terrae nullius Since: Nov, 2010
#11: Dec 13th 2010 at 2:37:11 AM

this syncs up with some of the world building I've been doing.

It was mostly an afterthought for me, to be honest. I want predator-riders now and probably winged people later on, and it suddenly occurred to me that making the people smaller goes a long way towards removing some of the main practical objections to both.

Another thing to note, as you get smaller, is body heat. Your hobbits will have a larger surface area for their volume and so will lose heat fast. I'm not sure whether the difference will be big enough to be noticeable, though.

Good call, hadn't thought of that. As it happens, that, too, works well in my setting. Yay.

The thing about mounts - the trouble with riding things like wolves and big cats is that their back bends much more when they run than a horse's does. The spine of the horse is very rigid, and I think that's the reason they're a safe and practical mount. A big cat would be very uncomfortable to ride, and I'm not sure how you'd fit a saddle to them.

I agree. The predators I have in mind are semi-intelligent and would only consent to be ridden occasionally and briefly (communal, mutually beneficial hunting, mostly), so I think I can get away with it. But it does make them less suitable for something like long-distance travel, no doubt about it.

ETA: Oh, regarding saddles, I'm envisioning the predator wearing a harness consisting mainly of a sort of collar and a sort of belt, with something like gauntlets attached to the former and something between stirrups and leather stockings attached to the latter. The riding posture would then be similar to bareback horse riding while the beast is moving slowly, sitting upright and holding on mainly by leg pressure. Once the beast begins to run or climb, the rider inserts their hands and forearms into the gauntlets, their feet and crura into the stockings, and takes almost all their weight off the animal's back.

How brainy are they, I mean their brain is only 1/8 the size of ours right?

Okay, there seem to be plenty of aspects I haven't fully thought through. Let's take it as a given that they're as brainy as we are: I'm not interested in writing them as a bunch of dimwitted savages. The question becomes if I need to make their heads bigger in relation to their bodies to make that plausible, and how much that throws off their balance.

How about real-world pygmies, do they have relatively bigger heads than taller peoples?

edited 13th Dec '10 3:06:08 AM by kassyopeia

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.
MattII Since: Sep, 2009
#12: Dec 13th 2010 at 12:13:00 PM

Pygmies are a group of people who grow to less than 5 feet tall, what you're talking about is people maxing out at about 80-90cm, so yes, you are going to run into brain-size issues, especially if you want to keep human proportions at that size. You could ignore it of course (so many do),but if you're looking for something totally accurate...

kassyopeia from terrae nullius Since: Nov, 2010
#13: Dec 13th 2010 at 4:19:51 PM

I didn't mean to imply that my hobbits would be similar to real pygmies. But looking at whether there actually is a correlation between brain size and intelligence for humans (on the ethnicity level, not the individual one) might be instructive.

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.
MattII Since: Sep, 2009
#14: Dec 13th 2010 at 7:15:16 PM

Good luck on that, I doubt even a neurologist could tell you that because we know so little about the brain.

kassyopeia from terrae nullius Since: Nov, 2010
#15: Dec 13th 2010 at 7:55:34 PM

I was looking more toward statisticians. The IQ-scale has many flaws, but it's better than nothing.

Scratch that, I have a better approach: We can look at closely related animal species of significantly different sizes, and see if they do exhibit significantly different levels of intelligence.

For example, let's consider a wildcat and a tiger. Or a dolphin and a blue whale. Or a goat and a buffalo.

If there is a correlation, I certainly wouldn't call it significant. That's good enough for me, for the time being.

edited 13th Dec '10 8:27:12 PM by kassyopeia

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.
Icalasari Warble from Alberta, Canada Since: Jan, 2001
Warble
#16: Dec 13th 2010 at 11:13:45 PM

Humans are intelligent due to the surface area of our brains

Whales have huge brains, but they aren't flying into space, now are they? ;P

Provided the brain has a lot more folds, you shouldn't need a significant increase in head size

I wonder what a strip tease from a creature made of souls would be like?
kassyopeia from terrae nullius Since: Nov, 2010
#17: Dec 13th 2010 at 11:20:30 PM

[up] Well, there was that one Star Trek movie... oh, never mind.

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.
LoniJay from Australia Since: Dec, 2009 Relationship Status: Pining for the fjords
#18: Dec 14th 2010 at 1:22:02 AM

They say some grey parrots have the intelligence of a human toddler, and parrot brains are tiny.

Be not afraid...
MattII Since: Sep, 2009
#19: Dec 14th 2010 at 3:11:17 AM

Birds are also not a good comparison since their brains are apparently so different from ours.

LoniJay from Australia Since: Dec, 2009 Relationship Status: Pining for the fjords
#20: Dec 14th 2010 at 3:43:05 AM

Hey, if there are possibly going to be winged hobbits in the setting, maybe that sort of thing won't matter so much.

Be not afraid...
MattII Since: Sep, 2009
#21: Dec 14th 2010 at 4:05:03 PM

6 limbs is even further away from any known than the difference between humans and birds.

LoniJay from Australia Since: Dec, 2009 Relationship Status: Pining for the fjords
#22: Dec 15th 2010 at 1:20:42 AM

That's true; You'd have to take that up with the original poster though.

Be not afraid...
GiantSpaceChinchilla Since: Oct, 2009
#23: Dec 15th 2010 at 1:46:18 AM

Would flying squirrel hobbits work?

kassyopeia from terrae nullius Since: Nov, 2010
#24: Dec 16th 2010 at 11:58:14 PM

Re hexapods: No, I wasn't going to throw basic anatomical principles out of the window. Think bats (maybe feathery-winged, depending on whether aesthetics or plausibility triumphs), not angels.

I thought of something else in the meantime: How would their size affect their pace of life? Should their biological processes (pulse rate, to pick the most obvious) be faster and their life=span shorter? If yes, what's a reasonable factor here? 2, 8, or something else?

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.
LoniJay from Australia Since: Dec, 2009 Relationship Status: Pining for the fjords
#25: Dec 17th 2010 at 12:01:51 AM

More and more similarities to my world-building smile

Pulse rate maybe sounds plausible; but I don't think you'd have to change their lifespan. As far as I know that hasn't been correlated with size.

Be not afraid...

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