Rats

[James Dick]

Okay, this question may seem a little simplistic for biologists, but
remember I am just an economist:

How do rats survive the enormous selection pressure placed on them by humans
(and rat poison). Surely Darwinian evolution does not explain this (ie
random variations is individuals allowing survival of the species). Would
Lamarkian evolution be a better explanation (ie Rats deliberately trying to
'beat' the poison)?

I find it curious that these species we deliberatly try to remove, yet
survive, while others that we don't deliberately try to kill become
extinct!!!

James

(I'm more interested in the first part of this question than the second part
by the way)