You can try darwinism in a nutshell by exposing bacteria to poisons. Some will survive for genetical reasons. You will have the results on the same day you are doing that experiment.

And that's how we make nature develop bacteria super-resistant to anti-biotics - by applying anti-biotics on a broad scale. Luckily our bodies kills bacteria without using anti-biotics (it is basically eating them) so those that survive the treatment with that medicine are killed by our immune system. But sometimes some escape.

So since discovery of anti-biotics in the early 20th centuries super-resistant bacteria strains no longer treateable by anti-biotics have appeared. It is likely that we won't be able to apply anti-biotics sucessfully for a couple of diseases in the next century.

That is evolution at work.

We human beings ourselves have evolved since we are here, at least some of us. Many europeans developed the ability to drink the milk of cows as adults - an ability scarcley found in people of african or asian origin. The property is called lactase persistence. And it wasn't there at the origin of mankind.