Summary
Behaviour that benefits others at a cost to the actor, explained by kin selection and reciprocity.
In depth
Biological altruism reduces the actor's fitness while raising the recipient's. Explanations: kin selection, reciprocity and group selection. Not about motives.
Altruistic acts spread when beneficiaries are relatives (kin selection), when roles are reciprocated or when actors gain indirectly. True altruism means fitness cost to the donor, regardless of intention.
Key idea: apparent self-sacrifice can be explained by gene-level selection.
Biological altruism is behaviour that raises another individual's fitness at a cost to the actor's own. It seems to conflict with natural selection but is explained by kin selection, where helping relatives spreads shared genes, and by reciprocity or group benefits.
Examples include alarm calls in ground squirrels, helpers at the nest and sterile worker bees. Hamilton's rule gives the condition under which such behaviour can evolve.
Example: a Belding's ground squirrel gives an alarm call that exposes it to predators but warns its kin.
Common mistake: assuming altruism evolves for the good of the species; selection acts on genes and individuals.
Frequently asked questions
What is Altruism?
Behaviour that benefits others at a cost to the actor, explained by kin selection and reciprocity.
Which area of biology covers Altruism, and how advanced is it?
Altruism is one of the 53 topics in Animal Behaviour. It is rated Intermediate, so it suits learners who already know the core vocabulary. Related topics in this area include Hamilton's Rule, Social Groups, Social Learning and Culture.
Can you give an example of Altruism?
Belding's ground squirrel females give alarm calls, especially near relatives.
What should I learn before Altruism?
Work through the Beginner topics in Animal Behaviour first, such as Animal Behaviour, Innate Behaviour, Learned Behaviour, then return to Altruism. Intermediate topics assume the Beginner vocabulary.
What topics are related to Altruism?
The closest topics to Altruism are Hamilton's Rule, Social Groups, Social Learning and Culture, Reciprocal Altruism. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Altruism?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Altruism. To practise the whole of Animal Behaviour, use the Animal Behaviour quiz.
How is Altruism different from Hamilton's Rule?
Altruism: Behaviour that benefits others at a cost to the actor, explained by kin selection and reciprocity. Hamilton's Rule: Altruism evolves when relatedness times benefit exceeds the cost, rb greater than c. Read both side by side and note what each one explains.
What is a common mistake about Altruism?
Assuming altruism evolves for the good of the species; selection acts on genes and individuals.
How should I study Altruism 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 Hamilton's Rule and explain the difference aloud. Finally, take the Animal Behaviour quiz and come back to this page for any question you miss.