What is Hamilton's rule and its significance?

What is Hamilton's rule and its significance?

• A. rb < c; altruism can never evolve.
• B. rb = c; altruism evolves only if costs equal benefits.
• C. rb > c; altruistic behavior can evolve if the cost to the actor is greater than the product of relatedness and recipient's benefit.
• D. rb > c; altruistic behavior can evolve if the relatedness times benefit to the recipient exceeds the cost to the actor.

Answer: (D)

Hamilton's rule concerns when altruism can evolve through kin selection. It says an altruistic act that costs the actor C will spread if the relatedness to the recipient, r, times the benefit to the recipient, B, exceeds the cost: rB > C. This reframing makes ancestral genes worth more when helping relatives because they share genetic copies. For example, helping a sibling (r ≈ 0.5) that increases the recipient’s reproduction by B is favored if 0.5 × B > C. The other statements misstate the condition: they either invert the inequality or treat equality as the rule, which doesn’t capture that a net inclusive fitness gain requires a strict greater-than, not just equality.

Hamilton's rule concerns when altruism can evolve through kin selection. It says an altruistic act that costs the actor C will spread if the relatedness to the recipient, r, times the benefit to the recipient, B, exceeds the cost: rB > C. This reframing makes ancestral genes worth more when helping relatives because they share genetic copies. For example, helping a sibling (r ≈ 0.5) that increases the recipient’s reproduction by B is favored if 0.5 × B > C. The other statements misstate the condition: they either invert the inequality or treat equality as the rule, which doesn’t capture that a net inclusive fitness gain requires a strict greater-than, not just equality.