Persistence of cancer over evolutionary timesis a challenging question for scientists. We explored herethe idea that cancer might result from negative trade-offs of adaptations that improve early survival and/orreproductive fitness. We focused on birth weight since thislife history trait has a genetic basis and is also associatedwith fitness benefits early in life, especially survival. Ouranalysis includes 107 to 109 countries, 46 types of cancerand various potentially confounding variables. High birthweight was associated with an elevated incidence of tencancers: kidney cancer, melanoma, multiple myeloma andpancreatic cancer, all four in both men and women, plusprostate and bladder cancers in men. These results, thoughcorrelational, suggest that antagonistic pleiotropy should beinvestigated further as a possible mechanism involved in thecausation of cancer in humans.