Time scale

IF everything was created from just a single organism and then multiplied and mutated to make all living things,how long did it take for the dinosaurs to be created from the start?seems to me theyre huge and too big for the purpose,but the purpose of what though. as the title says how long did it take for these organisms to multiply and mutate to make these monsters?also if Trex was primarily a scavanger,why so big,smaller creatures have more food compared to bigger ones

if the big comet (supposedly) the one that wiped out the dinosaurs didnt hit,would we have dinosaurs here today?

sorry if this has been started or talked about in previous threads,but i cant seem to subscribe to any so if i posted somewhere i would get lost to where i posted it

Well the Earth goes through natural temperature and CO2 cycles which modern science has deduced from ice core sampling.

Conditions for dinosaur life would have been tropical ... it is the ice age that killed them off. The question is what causes ice ages?

If we imagine that the comet was responsible for kicking off the glacier formations, then, if the comet had never hit, and everything else was held constant, then yes we'd probably be Tyranosaurus Rex bait, although we might have killed certain species off out of defensive survival needs, sort of like we don't see bears wandering out onto main street like in the old days.

If actually the comet was only part of the picture, and there are longer term cycles due to modifications in the Earth's orbit and solar cycles, then it was inevitable, and it is only the hardiness of the human species that enables their ability to acclimitize or else invent technologies that provides us the ability to endure a wider range of climate fluctuations.