Basically i just saw a post about a massive black widow spider living in an electrical box and it got me thinking. Why is growth limited to a “general size” in most cases? Is it just natural genetic code that says ” You will only grow this much and no more”, or does it all depend on stuff like environment, nutrition, risk factors, etc?
In: Biology
Any given body plan only works in a fairly narrow range of sizes. The larger you get, the bigger your weight, which increases as your volume increases. However, your leg strength for example would only increase as its cross-sectional area increases. Volume is a cube, area is a square, so volume/weight increase much faster than the supportive strength of your legs and your musculo-skeletal system. In real life, Godzilla should be mostly legs.
Creatures grow in response to signals called growth hormones. When the body is producing those hormones, it signals all the cells that they should be reproducing faster and spending more energy on growth.
When (and how long) creature produces these signals depends on genetics and environment. For example, if a creature lives in near starvation, the body will likely stop growing, or at least slow the rate of growing.
That’s because growing takes a lot of resources away from other functions in the body.
What if you give an animal access to infinite food, would it grow infinitely? Sort of. If you keep feeding an animal beyond its capacity to grow, it will store excess energy as fat to save for later.
However, the actual *frame* of a creature has a maximum size set by genetics.
“Creatures” is a pretty broad term. That fusebox black widow was only about as big as a small wire nut. Insects and arachnids have a directly limited size due to real mechanical cube:square limitations of their exoskeletons and ability to metabolize oxygen that’s why undersea arthropods like crabs can become much much bigger – but we’re generally less afraid of them I guess because we see them as delicious and we don’t encounter them as much.
Creatures like some fish eg carp can grow much larger than you would expect given adequate nutrition and space but they still have an upper limit to their size – while mammals are much more governed by their genetics and, although having a normal range of sizes, will still have a potential to be much larger or smaller according to genetics.
Take dogs for an extreme example. They’ve been selectively bred since prehistory and according to their genetics can grow to be as tiny as a chihuahua or as large as a mastiff.
The Square cube law. The Square of the animal x^2 must support the volume of the animal x^3. (Somewhat negated/altered by water)
https://en.wikipedia.org/wiki/Square%E2%80%93cube_law
Another factor is oxygen which may be unique to insects I don’t know all the details but insects grow larger in oxygen rich environments.
this video touches on dogs specifically. but in general larger size requires more caloric intake. so creatures found an equilibrium with what their environment provides. https://youtu.be/tlp8pa1Ry9A?si=D0oRAhOOpJ9yVihn
I’m subscribed to Hogwarts Legacy subreddits, and came in here thinking it was that!
Anyway, the answer is they have babies and adults and it’s enormously more simple to keep those two varieties around, so you can be specific about the way they interact etc, than to develop many different sizes for growth over time.
Every now and then a massive cow, lion, dog etc is born but usually stands at a massive disadvantage in the wild and never lives long enough to pass on its dna. Natural selection kinda creates a cap on the max size of every animal. If it’s advantageous for them to get bigger then that’ll happen over time but it requires a pretty specific situation. Theoretically any animal can be selectively bred to be giant, like we could have giant house cats or chihuahuas if we put enough time and money into it.
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