according to science.if an animal such as a lizard monkey etc were huge

they would not be able to sustain there own size and weight and would fall apart under its own weight, also the lizards hide would not have been significantly thicker to withstand a strike from a human. the human body is remarkably strong. a Thai boxer can strike with enough force to lift a car off the ground. and a lizard as large as that would literally have joint and bone issues. so a punch from the rock( a few hundred lbs of force maybe over a thousand psi) would actually do a good deal amount of damage