"The idea that species gradually change over many generations is the cornerstone of biology. This is how we know it's true."

This is for the know-nothing science deniers, a copy and paste job from BBC News:

Evolution is one of the greatest theories in all of science. It sets out to explain life: specifically, how the first simple life gave rise to all the huge diversity we see today, from bacteria to oak trees to blue whales.

For scientists, evolution is a fact. We know that life evolved with the same certainty that we know the Earth is roughly spherical, that gravity keeps us on it, and that wasps at a picnic are annoying.

Not that you would know that from the media in some countries, where evolution is ferociously argued about – put down as "just a theory" or dismissed as a flat-out lie.

Why are biologists so certain about this? What is the evidence? The short answer is that there is so much it's hard to know where to start. But here is a very cursory summary of the evidence that life has, indeed, evolved.

The rest of it is here: http://www.bbc.com/earth/story/20150803-how-do-we-know-evolution-is-real

"Not that you would know that from the media in some countries, where evolution is ferociously argued about – put down as 'just a theory' or dismissed as a flat-out lie."

Those backwords countries include Idiot America where I live. This country is infested with dense people who are afraid of science. Reality makes them cry.