The units of selection problem has two general themes :
- what is the "unit" on which selection operates?
- how do you identify it?
- how do you explain altruism?
- the individual creature
- the individual gene
- "groups" of creatures
- the "trait"
What explains apparent altruism in animal behaviour? (Altruism is a problem for a naive Darwinian theory because altruistic decrease one's relative fitness, so why should they have evolved?)
- mutualism - ie. acts which increase the relative fitness of others but also increase your own. Symbiosis between members of different species. Herding and huddling together for warmth, etc.