Take male strategies for success in the world. If you've got all the advantages, if you're attractive and clever and all of that, you will generally go for very high quality females.

Just as the design of our bodies can be understood only in terms of natural selection, so the design of our minds can be understood only in terms of memetic selection.

Imagine a world full of brains, and far more memes than can possibly find homes. Which memes are more likely to find a safe home and get passed on again?

If everyone understood evolution, then the tyranny of religious memes would be weakened, and we little humans might find a better way to live in this pointless universe.

The sale of sex in modern societies is not about spreading genes. Sex has been taken over by the memes.

In proportion to our body mass, our brain is three times as large as that of our nearest relatives. This huge organ is dangerous and painful to give birth to, expensive to build and, in a resting human, uses about 20 per cent of the body's energy even though it is just 2 per cent of the body's weight. There must be some reason for all this evolutionary expense.

Finally, we might decide that civilisation itself is worth preserving. In that case we have to work out what to save and which people would be needed in a drastically reduced population - weighing the value of scientists and musicians against that of politicians, for example...