I find it oddly appropriate that this thread points to a symbolic proof of evolution.
A mutant form of Mudcatter, known as 'obstreperous prick', by its nature, poisons the environment. This results in other, less hardy forms of Mudcatter seeking refuge in other environments and so gradually becoming extinct here.

Or in other words, when enough people piss in the pool, the only people left will be those who like to swim in piss. Not a whole lot different than the theory that eventually cockroaches will be the only living thing on Earth, although roaches won't have caused the environmental toxicity... but the roaches aren't intellectually advanced enough to care, either.