In ages past, planet Earth was dominated by the reptiles, but a worldwide catastrophe wiped out a few species (the ancient dinosaurs).
Humans now rule the planet, and we've been able to populate almost all parts of the planet because of these reasons:
1) We use technology to help us adapt to new environments.
2) Our way of reproduction means that eggs would not be stolen by predators, unlike the reptiles whose eggs were either stolen or eaten by other creatures and usually only a minority of even none of the eggs are able to hatch, making it difficult for a species to continue to grow...
In the future, after the human race has been wiped out by either:
1) A terrorist threat
2) Lost of environment due to natural/artificial disasters
3) Chemical/Nuclear warfare
4) Extraterrestrial Influence (Asteroid Impacts)
I believe that the next group of creatures that would reign over the planet would be the Insectoids because:
1) Exoskeleton (Great adaptability to extreme environs)
2) Small Size (Able to hide in many places, better the chance of survival)
3) Colonies (Like termites, ants, great team effort and work will allow the insectoids to thrive in this new world)
i mean, cockroaches existed since the dinosaur ages.
Six Sentinels, do you believe in creationism?