A young woman in her teens has about 300,000 eggs in her ovaries. By the time she is menopausal, none are left.

Religion has endured since the dawn of human consciousness precisely because it encompasses so much of being human. No idea has endured so long, gathered up so many disparate needs and wants and feelings, and inspired so many different paths towards understanding it.

Women of child-bearing age steadily run out of eggs by the continuous process of cell death. While reading a copy of the Guardian carefully from cover to cover, a normal woman will have lost on average two eggs - while, typically, a normal man will have made 70,000 new sperm.

I do not know of any credible evidence that suggests Dr Zavos can clone a human being. This seems to be yet another one of his claims to get repeated publicity.

To build and strengthen new connections, the brain needs the challenge of fresh and unusual stimuli. .... There's a lot of evidence to suggest that repetition is bad for brain health, and novelty is good.

Over the past 20 years, I have presented many science programmes on BBC1. But none is, I think, more socially important, or of more human interest, than this ongoing series of 'Child of Our Time.'

We are more dependent on science and engineering than at any other time in history. However, there is plenty of evidence that far too many people are scientifically illiterate, often having been put off science at school.