Peto's paradox is the observation that, at the species level, the incidence of cancer does not appear to correlate with the number of cells in an organism.[1] For example, the incidence of cancer in humans is much higher than the incidence of cancer in whales,[2] despite whales having more cells than humans. If the probability of carcinogenesis were constant across cells, one would expect whales to have a higher incidence of cancer than humans. Peto's paradox is named after English statistician and epidemiologist Richard Peto, who first observed the connection.