[stonedape]

Originally Posted by Mac Hiavellian

Wasn't there a lot more toxic gases in the air all those years ago thus why dinosaurs were so big and that would mean they wouldn't survive nowadays?

There was a lot more oxygen in the air which allowed larger species (Oxygen's also what also what allowed larger species in general after plants oxygenated the environment enough). But that doesn't mean dinos necessarily couldn't live in our environment, they just wouldn't be selected for in nature as a population.

We know humans and dinosaurs never co-existed because of the distinct fossil record, we don't even have to get into the old chestnut of radiometric dating. No one would know what you were talking about if you described a dinosaur until the 19th century.