[geysersam]

I've heard a hypothesis that cancer behavior is not primarily evolved in the patient, but instead it is an ancient mechanism from the time of transition from single cell to multi cell organism.

A human cell can never survive on its own. But there might have been a time when cells could have benefited from "pulling the escape hatch" and taking their chances instead of continuing cooperation within a damaged early multicellular organism.

[dredmorbius]

I'd love to see a source on that if you have one handy.