From an interview with David Attenborough in the current edition of 'New Humanist':
Yet he had never openly declared himself to be an atheist. “That’s right. I’m an agnostic. In the strict sense that I don’t know. And I don’t know a lot. And I certainly don’t know about the existence of a supreme being or about the existence of an afterlife. The absence of evidence does not mean that there is a god. The absence of evidence means two things. It means that we don’t know but it also means scientifically that it would be interesting to find out.” There are those who accuse agnostics of hedging their bets. But this would quite unfair to Attenborough. His agnosticism is not a way of saying that there might be a god; it is rather a statement about the necessary humility and open-mindedness of the scientific attitude. It is a prescription for action rather than a refusal to enter the argument.