Giant Animal Bones Vs. Metals

I had a thought the other day: giant animals in general seem like they'd make non-metalworking cultures more competitive with metalworking ones, what with the much greater physical and mechanical strength of their bones from which tools, weapons, and armour could be made.

This post is me doing some basic math to get a quick idea of just how comparable giant animal bones and metal might be as materials.

First, the square-cube law: When an object undergoes a proportional increase in size, its new surface area is proportional to the square of the multiplier and its new volume is proportional to the cube of the multiplier. Stated simply: if you take a guy and make him twice as tall, his mass will increase eight times over. Unless you change up his proportions some, this is going to be hell on his knees - in fact, the average human thighbone can bear up to about ten times the average human weight before breaking, so our 2x giant is cutting it very close indeed.

A number of factors can affect bone strength - its macro- and micro-structure, chemical composition, etc. One of the most important of these factors is bone thickness - compare the bones of a person and an elephant, for example - but I don't think this would affect the bones' strength so much when they've been worked into most sorts of tools. Therefore, giant animals which retain similar proportions to their base-size animals will likely have the most useful bones when it comes to competing with metal or stone.

Let's work through an example: At 26 feet, a storm giant is 4.33 times taller than a 6-foot tall man, and thus 81.18 times heavier (~14,207 pounds, assuming man's weight is 175 pounds), without much change in proportions based on most pictures of storm giants.

Artstation - Ruben Smith

Assuming the giant's bone structure is largely the same, with his thighbone 4.33 times stronger than the man's based on cross-section density, it'll be able to handle about 26,000 pounds of compressive force - maybe enough for the giant to walk without breaking its own legs, but this is only based on the strength of the thighbone, and not the feet/tendons/spine/etc. Also, storm giants are often depicted wearing metal armour, which would also be much heavier than a person's armour, so they'd have to be able to carry that around too without buckling under the stress - so their bones and other tissues must be much stronger than proportions would suggest.

To get an idea of how much stronger, let's put that giant under a bit more stress by making him jump up and down. If my back-of-the-napkin math is accurate, this will apply 139,229 Newtons of force to his thighbone - well above the bone's ability to withstand 113,299 Newtons. Should have stuck to walking, Shaq.

Our average man, by comparison, would have his thighbone withstand 774 Newtons, well within his max tolerance of 26,166 Newtons. The ratio of the giant's thigh strength vs. force is 1.23 - the man's 0.03. Therefore to be able to move about as well as the man, the giant's bones must be about 41 times stronger, rather than 4.33 times. Let's see how that compares to metals.

Ultimate Tensile Strength:
Human bone - 130 MPa
Steel - 2,693 MPa (upper end)
Giant bone - 5,330 MPa

Compressive Strength:
Human bone - 131 MPa
Steel - 1,500 MPa (upper end)
Giant bone - 5,371 MPa

I didn't expect the difference to be this extreme! What could make bones this strong? Reinforcement with strontium instead of calcium? Carbon nanotubes? Perhaps a bigger nerd would know. I don't even know how you'd begin to work bones this strong.

This is of course on the extreme end - most dire animals in D&D I could find the measurements of were only 4-8x larger than their base-size animal, and there's smaller giants like hill giants, etc. There are properties like ductility and conductivity where metals would be preferable to giant bones, but in general metalworkers are going to be mogged by bonemongers.

If my math's off, feel free to pop off in the comments.