Carl Zimmer raises a fascinating question:
Blue whales can weigh over a thousand times more than a human being. That’s a lot of extra cells, and as those cells grow and divide, there’s a small chance that each one will mutate. A mutation can be harmless, or it can be the first step towards cancer. As the descendants of a precancerous cell continue to divide, they run a risk of taking a further step towards a full-blown tumor. To some extent, cancer is a lottery, and a 100-foot blue whale has a lot more tickets than we do...
Yet there seems to be no correlation between body size and cancer rates among animal species. We run a thirty percent risk of getting cancer over our life time. So do mice, despite the fact that they’re 1000 times smaller than we are. All animals studied so far have cancer rates in that ballpark. (And yes, sharks do get cancer.)
Caulin and Maley argue that when animals evolve to larger sizes, they must evolve a better way to fight against cancer.