Can you be more specific? I've heard the argument, for example, that cell death is a defense against tumor growth, but we do not observe that across all living

Can you be more specific? I've heard the argument, for example, that cell death is a defense against tumor growth, but we do not observe that across all living things - we have Peto's paradox where large animals have almost no incidence of cancer. I'd be really hesitant to try to attribute any one specific reason as to why we age, or why that has benefited some life.