Opponents say natural selection is not a theory supported by observation or experiment; that it is not based on fact; and that it cannot be proved. Well, no, you cannot prove the theory to people who won't believe in it any more than you can prove that the Battle of Hastings took place in 1066. However, we know the battle happened then, just as we know the course of evolution on earth unambiguously shows that Darwin was right.

[W]hen we look at the graphs of rising ocean temperatures, rising carbon dioxide in the atmosphere and so on, we know that they are climbing far more steeply than can be accounted for by the natural oscillation of the weather ... What people (must) do is to change their behavior and their attitudes ... If we do care about our grandchildren then we have to do something, and we have to demand that our governments do something.

The question is, are we happy to suppose that our grandchildren may never be able to see an elephant except in a picture book?

We really need to kick the carbon habit and stop making our energy from burning things. Climate change is also really important. You can wreck one rainforest then move, drain one area of resources and move onto another, but climate change is global.

We keep putting on programmes about famine in Ethiopia; that’s what’s happening. Too many people there. They can’t support themselves — and it’s not an inhuman thing to say. It’s the case. Until humanity manages to sort itself out and get a coordinated view about the planet it’s going to get worse and worse.

I have no doubt that the fundamental problem the planet faces is the enormous increase in the human population

Crying wolf is a real danger.