Evolution is a process that normally takes hundreds of millions of years, but there are a few exceptions. Within our lifetimes, microscopic organisms such as bacteria are constantly evolving. Quite often this is to our detriment, as disease-causing bacteria evolve to become resistant to anti-bacterial drugs created to destroy it.

A stunning new video by a team of researchers at Harvard Medical School visualises this exact phenomenon. The team divided a petri dish into nine layers with varying levels of anti-bacterial drugs in them.

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Bacteria was introduced into this environment and in the first few layer where the concentration of drugs was less, they began multiplying rapidly. They stopped at the layers where concentration was greater, and the bacteria found it difficult to survive.

Until, that is, the first mutant was created. And then another. And then the entire petri dish was filled with drug resistant bacteria.

Drug-resistant strains of diseases are being increasingly found all over the world. Here is a Ted-ed video explaining how that happens.

The problem is not with the antibiotics, but the bacteria they were made to fight and the reason lies in Darwin’s Theory of Natural Selection. As the non-resistant bacteria are killed off, which happens especially quickly in antibiotic rich environments, like hospitals. There is more room and resources for the resistant ones to thrive, passing along only the mutated genes that help them do so. Reproduction isn’t the only way to do this. Some can release their DNA upon death to be picked up by other bacteria, while others use a method called conjugation, connecting through pili to share their genes. Over time, the resistant genes proliferate, creating entire strains of resistant super-bacteria.

News of "nightmare" bacteria, which is resistant to most kinds of drugs, is also becoming increasingly common.

It was long seen as a problem affecting developed countries because of their over-use of antibiotics. But a 2015 study found that India is a hotbed of biotic resistance. In a Ted Talk, journalist and author Mary Mckenna, pointing out that mankind has lost the advantage of antibiotics, explains the things we can still do as we begin living in a post-antibiotic world.

We could forgo giving an antibiotic if we're not sure it's the right one. We could stop insisting on a prescription for our kid's ear infection before we're sure what caused it. We could ask every restaurant,every supermarket, where their meat comes from. We could promise each other never again to buy chicken or shrimp or fruit raised with routine antibiotic use, and if we did those things, we could slow down the arrival of the post-antibiotic world.

But we have to do it soon. Penicillin began the antibiotic era in 1943. In just 70 years, we walked ourselves up to the edge of disaster. We won't get 70 years to find our way back out again.