The Science of Giants...

[Vardukson]

Hi All,

I'm trying to create a fantasy setting with a realistic sort of giants. They're supposed to be about twice the height of a regular human, but I was hoping that I could make them biologically sound, so if they actually existed, they wouldn't be crushed by their own weight or whatever.

Has anybody tried to do this? Or know where I might find the information to do this myself? I just don't know that much about biology to know what a creature like that would need to survive as a species.

[laguna]

as you seem to be aware, if you double something's size, you quadruple it's weight without strengthening the materials it's made of. the result is eventual collapse.

the easiest solution i can think of for creatures of unlimited size is that every time you double it's size, you also double the density of whatever it's made of. hence, with double the density AND double the size, the framework of the organism will be able to handle quadruple the weight.

that's just my theory though, somebody who knows physics would have to confirm my thoughts.

[Vardukson]

Well, I'm kind of hoping I can work around using super-dense substances or anything like that. I'd still like them to be made out of normal animal meat and stuff. Just, I guess, like, eh, I don't even know which questions to ask.

Something like, how much thicker would it's bones need to be to hold up that weight? How much bigger would it's muscles need to be?

A friend of mine mentioned that they'd need to have a way to cool off, because they'd overheat easily. But I don't know how he knows that, or if it's true.

How did dinosaurs manage to be that tall without killing themselves?

[munin]

GURPS Bio-Tech has some good info about realistic larger humanoids (pp. BIO62-64). Larger size is justification for increased ST (+10 for scale x2) and Temperature Tolerance (higher volume to radiating surface ratio). Larger creatures eat larger meals but less frequently (a scale x2 giant would eat 1.5 meals per day, each 8x the weight of a human's meal).

Also see Gulliver Mini.

[lwcamp]

Originally Posted by Vardukson

Hi All,

I'm trying to create a fantasy setting with a realistic sort of giants. They're supposed to be about twice the height of a regular human, but I was hoping that I could make them biologically sound, so if they actually existed, they wouldn't be crushed by their own weight or whatever.

Has anybody tried to do this? Or know where I might find the information to do this myself? I just don't know that much about biology to know what a creature like that would need to survive as a species.

What nature does is increase the thickness of the limbs and torso faster than the height/length. This results in the thickness increasing as the height/length to the 1.5 power, cross sectional areas increasing as the height/length cubed, and weight increasing with height/length to the fourth power (approximately - the above scaling is called constant strain similarity, and seems to apply to a good approximation over a wide range of size scales for a great many body types). Thus, if you scale up a 1.7 meter, 80 kg human male to 3.4 meters (twice the height), the giant would be 70 kg * 2 * 2 * 2 * 2 = 1,120 kg, or a bit over a ton in weight. If the human had a torso 20 cm front to back and 30 cm side to side, the giant would be 20 cm * (2^1.5) = 57 cm front to back and 30 cm * (2^1.5) = 85 cm side to side.

At 3.4 meters tall, blood pressure will start to be an issue. The giant will need special elastic integument on its legs and feet to keep blood from pooling in its feet. Changing posture quickly could result in dizziness or unconsciousness as its blood pressure rapidly falls before its heart can respond by pumping harder to get blood to the brain.

So far I do not see any deal breakers. Giraffes get 4 to 5 meters in height, and there is some evidence that the largest sauropods were able to rear up to 15 meters in height. Meanwhile, the largest bipeds were in the vicinity of 8 to 10 tons. Your giant is not pushing any of these extremes. It should be quite viable.

Luke

[Verjigorm]

Would additional hearts help?

[laguna]

Originally Posted by Vardukson

Well, I'm kind of hoping I can work around using super-dense substances or anything like that. I'd still like them to be made out of normal animal meat and stuff. Just, I guess, like, eh, I don't even know which questions to ask.

Something like, how much thicker would it's bones need to be to hold up that weight? How much bigger would it's muscles need to be?

A friend of mine mentioned that they'd need to have a way to cool off, because they'd overheat easily. But I don't know how he knows that, or if it's true.

How did dinosaurs manage to be that tall without killing themselves?

well, as you say, you could mitigate the need for denser materials for a while, i'm still vague on the physics here but i'm thinking if every time you doubled his height, you quadrupled his width (most importantly bones). but if you look at the dimentions of a creature after doubling height and quadrupling width a couple of times, the width gets ridiculous looking.

also, (really do need confirmation on this part) isn't there a point that can be reached where bone is simply not hard enough to support X weight, no matter how thick the bone is?

lastly, a big help to the dinosaurs surviving was the fact that they were lizards. cold blooded animals don't have overheating problems and don't have to constantly burn calories maintaining body heat.

I would recommend the high-density material route though, giants are a much greater threat when they have a little extra DR.

[laguna]

yeah, i'll defer to lwcamp on this one.

[whswhs]

Originally Posted by Vardukson

Hi All,

I'm trying to create a fantasy setting with a realistic sort of giants. They're supposed to be about twice the height of a regular human, but I was hoping that I could make them biologically sound, so if they actually existed, they wouldn't be crushed by their own weight or whatever.

Has anybody tried to do this? Or know where I might find the information to do this myself? I just don't know that much about biology to know what a creature like that would need to survive as a species.

How realistic do you want to be?

GURPS Fantasy offers rules for a moderately realistic treatment: ST is proportional to longest body dimension (so a 2-yard man has ST 10 and a 12-yard giant has ST 60), BL goes up as the square of ST, and body weight goes up as the cube of ST (the man has BL 20 lbs. and weighs 150 lbs.; the giant has BL 720 lbs. and weighs 32,400 lbs.). This respects the square-cube law and has giants constrained to carry small loads in proportion to their body weight, whereas a tiny critter can carry a proportionately large load (an ST 1 spider weighs 2-3 ounces and has BL just over 3 ounces). There are more details in Chapter 3 of GURPS Fantasy.

If you want a hyperrealistic treatment, you are going to want to read biology textbooks; look up Vogel's Life's Devices and Peters's The Ecological Implications of Body Size, the first for the underlying science, the second for the statistical correlations. A fairly close approximation is based on the need for a pillar to get proportionately thicker as its length increases, to avoid buckling: cross-sectional limb thickness varies as the cube of length, body weight varies as the fourth power of length, and lifting strength varies as the cube of length. GURPS rules aren't really set up to do this elegantly.

The GURPS Low-Tech companions will contain a different scaling system, one designed to have a 60 foot giant wield a 30 foot sword with exactly the same ease as a 6 foot man wields a 3 foot sword. There is no way to do this realistically, and while I kibitzed with the discussion, I ended up washing my hands of it, because I couldn't stretch my imagination that far.

Bill Stoddard

[Verjigorm]

Originally Posted by laguna

lastly, a big help to the dinosaurs surviving was the fact that they were lizards. cold blooded animals don't have overheating problems and don't have to constantly burn calories maintaining body heat.

Dinosaurs were NOT lizards. They were Reptiles. Also, after a sufficient body mass is reached, being cold-blooded doesn't really matter: your body is just massive enough to generate heat and keep you moving. This does mean that large reptiles like the Dinosaurs(if they weren't actually warm-blooded, which alot of research also supports) were effectively warm-blooded.