re: Another T.Rex question.
At this level, hundreds of thousands of years can look like a sharp, delineated line in the fossil record. Nobody knows when the last dinosaur died, but it seems logical that an herbivore would last longer than a large carnivore.
We may be at the top of the food chain (at least as far as macroscopic creatures go), but we're a bit more flexible than a Tyrannosaurus. For one thing, we're omnivorous. Also, we can live successfully without high tech in environments from the deep desert to the arctic.