Animals that live in social colonies are known to age much slower than non-social animals. For example, naked mole rats are small rodents that hardly suffer from ageing and live in social colonies. Are these social species more likely to become long-lived, or are long-lived species more likely to become social? Analogously to how individuals cooperate to form breeding colonies in social species, at some point individual cells started cooperating to form multicellular organisms (like humans!). Did the evolution of cellular cooperation change the ageing rates of our cells when multicellularity evolved?