All right. Thanks for all of the good answers about why we have never had really, really huge?

Question

animals on earth ---- 35 miles long and 18 miles wide ----. Most of you are right about most of your ideas, however, I think that most of your positions depend on "the size of the earth in relation to gravity. For example, it was pointed out that an animal that big could not move fast enough to avoid attacks. Why? Because of gravity which is related to the size of the earth. I think MAN is sized "just right" to take advantage of the size of the earth and the gravity it produces. What do you think?

Answer 1

There's also something called the "Square Cube Law" which effectively limits the size of land animals.

As size increases and proportions remain the same, the volume of an organism increases as the cube of the linear measure, while the area (cross section of muscle etc,) increases as the square.

The effect of this is that if we had an ant, say, increasing in size to being 50 feet long, it could neither move an inch or even breathe.

Answer 2

First of all, an animal with the dimensions you described would be so massive, it itself would have a significant amount of gravity. So, not only would the earth be holding that animal, the animal would also be holding the earth. This means a lot of force pulling the earth and the animal together. So, if an animal was that big and it was somehow still alive under all that force, than it would either be really flat (so it doesn't crush itself under it's own weight) or it would have incredibly thick, dense bones or other support structure, just to hold it up. If that were the case than I bout it would move much, which leads to another thing: food. An animal that size would require a huge amount of food, and since all multi-cellular animals don't photosynthesize, the animal would have to move around and eat, but with an animal that size, i doubt that it would eat enough food after moving a distance to equal how much energy it burned getting there. It would take a lot of energy just to keep it's own weight off of it's lungs so it could breath, and in breathing it would need an increadible amount of air.

So, those are a bunch of reasons why an animal like that wouldn't exist. Another answer is because an animal doesn't need to grow that big for protection from predators, and a smaller body size is much easier to maintain with food and water.

Answer 3

You won't get any arguments about that. Everyone agrees that the creatures which live on Earth are perfectly suited to their environments--it's just a question of whether they evolved to fit the Earth or the Earth was created to fit them.

Answer 4

We might be sized just right, but in reality we're one of the most vulnerable creatures on earth. Without weapons, just about anything can harm us. Save for squirrels, maybe.