In Chapter 5 we sketched the basic way in which cells process information from the outside world and the fundamental controls of the cell cycle. In principle, a mutation in any part that accentuates a positive or eliminates a negative could make a contribution to cancer. As a result of the amazing advances in DNA sequencing that we described in Chapter 4, we now know that most tumour cells accumulate tens of thousands of mutations, and so heterogeneous are tumours that every cell has a unique genome sequence. This implies that the longer you live, the more likely it is that a cancer will appear somewhere in your body – but the up-side is that two in every three only do so after the age of 60. Seventy-odd years ago the Finnish-born architect and amateur historian Carl Nordling drew a graph plotting the number of cancer deaths against the age at which they occurred. Result: a straight line. Remarkably, this holds true for pretty well every major cancer, regardless of country, sex or race.