In the future, once we’ve totally wrecked the climate leading to resource wars and the massive die-off of human beings due to lack of water, starvation, and conflict, and earth is basically a big hellscape (so, like 2100-ish?), it’s not the cockroaches that will be taking over. It’s fungus.
Because let’s face it, fungus is much better at survival than us. Fungi survive in extreme temperatures all over the earth. Some have even survived vacuum. A fungal colony can become huge and live a very long time – consider this 90 acre fungus that is believed to weigh about 400 tons and be 2,500 years old in Michigan. It’s not even the biggest we know about.
And let’s not even think too hard about the ability of some fungi to change animal behavior in ways that are bad for the animal but help the fungus reproduce. (And given half a chance it will happily live all over and within your body.)
We’re fragile little gnats by comparison. We could nuke ourselves and there’d still be fungus around. Fungus is ultimate horror movie critter and no doubt the ultimate inheritor of the earth. Sorry, fellow mammals.