>At the same time, everybody seems to accept that the chance of getting cancer in your lifetime has risen to about one in three for men and one in five for women. And nobody knows why.

There is a clear and well known pair of reasons for this. First people are living longer and the longer you live the more prone to cancer you are. People who died of small pox did not die of cancer.

Second, more controversially, atmospheric bomb testing in the 50's and 60's.