Summary
Altruism evolves when relatedness times benefit exceeds the cost, rb greater than c.
In depth
rB > C. Relatedness r is 0.5 for siblings and 0.125 for cousins. It explains worker sterility and cooperative breeding, but debates continue about inclusive fitness versus other models.
Costs and benefits are measured in lifetime reproductive success. Relatedness r is the probability that an allele is shared by common descent. The rule also underlies parent-offspring conflict and nepotism.
Remember: inclusive fitness sums direct and indirect effects on genes.
Frequently asked questions
What is Hamilton's Rule?
Altruism evolves when relatedness times benefit exceeds the cost, rb greater than c.
Which area of biology covers Hamilton's Rule, and how advanced is it?
Hamilton's Rule is one of the 53 topics in Animal Behaviour. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Cooperative Breeding, Game Theory in Behaviour, Parental Investment.
Can you give an example of Hamilton's Rule?
Helpers at the nest in Florida scrub jays are mostly relatives.
What should I learn before Hamilton's Rule?
Work through the Beginner topics in Animal Behaviour first, such as Animal Behaviour, Innate Behaviour, Learned Behaviour, then return to Hamilton's Rule. Advanced topics assume the Intermediate vocabulary.
What topics are related to Hamilton's Rule?
The closest topics to Hamilton's Rule are Cooperative Breeding, Game Theory in Behaviour, Parental Investment, Reciprocal Altruism. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Hamilton's Rule?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Hamilton's Rule. To practise the whole of Animal Behaviour, use the Animal Behaviour quiz.
How is Hamilton's Rule different from Cooperative Breeding?
Hamilton's Rule: Altruism evolves when relatedness times benefit exceeds the cost, rb greater than c. Cooperative Breeding: Helpers other than parents assist in raising young, as in meerkats and some birds. Read both side by side and note what each one explains.
How should I study Hamilton's Rule step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Cooperative Breeding and explain the difference aloud. Finally, take the Animal Behaviour quiz and come back to this page for any question you miss.