Why were animals and insects so much bigger during the time before humans?

Question

Why were animals and insects so much bigger during the time before humans?

In: Biology

Answer 1

I suspect a lot of it is due to survival of the fittest with primitive animals. Survival mostly came down to physical strength and so size often wins. Certain animals evolved to larger sizes, until they developed venom, at which point they evolved to smaller sizes since they no longer needed to crush their prey. You might notice that shorter people can be kind of nasty. OK, that last sentence was a joke.