Kin Selection and Inclusive Fitness
W.D. Hamilton · 1964
"Evolution doesn't just favor genes that help the individual survive — it favors genes that help copies of themselves survive, wherever they happen to sit, including in relatives."
Hamilton solved a problem Darwin admitted he couldn't: why do animals sacrifice themselves for relatives? In 1964 he showed evolution favors genes, not individuals — and genes exist in relatives too.
Hamilton's inclusive fitness reframes selection around the gene, not the organism. A gene that lowers an individual's own survival can still spread if it sufficiently boosts survival in relatives carrying copies of that gene — Hamilton's rule: favored when cost to the actor is less than benefit to the relative, discounted by relatedness. This explained altruism in ants, bees, and humans without group selection.
What problem did Hamilton's theory of inclusive fitness solve that pure individual-survival selection couldn't explain?
Read more about the topic
The explanation above is written with AI assistance. These are the originals — go to them to check it.
- The Genetical Evolution of Social BehaviourWikipedia
- Kin selectionarticle
On the Origin of Species: Natural Selection
"Complex life needs no designer — small heritable advantages, repeated over enormous time, are enough to build every organism on Earth."