Unit of Selection
Reading 1 –
The Units and Levels of Selection by Samir Okasha (Ch 8, A Companion to Philosophy of Biology)
Traditional Darwinian View – * Though Darwin treats individual organisms as basic unit of selection, other possibilities can be seen * Lewontin (1970) – Natural Selection will operate on any level that exhibits ‘heritable variation in fitness’. * Hence the question of level seems purely empirical – but is not.
Historically – * The debate of Levels of Selection can be traced back to Darwin himself – Descent of Man (1871) – tries to explain ‘altruist behaviour’ based on selection at group level. * Weismann has also shown a similar thinking of hierarchical levels of selection. * G. C. Williams in Adaptation and Natural selection (1966) attacked the idea of group selection regarding it to be a weak evolutionary force as compared to individual selection – Pointed out that only a concept of between-group selection can be an evolutionary force * Hamilton – Kin Selection * Hamilton and Williams – ‘Gene’s eye view’ – Popularised by Dawkins (1976)
The Gene’s Eye View – * Hamilton – Altruistic behaviour towards related organisms. Relatives share same genes, hence the beneficiary of the act will be carrying same gene as the actor – Kin selection. * Hamilton’s rule – Altruism favoured by selection as long as cost incurred by the altruist is offset by sufficient amount of benefit to a related organism. bc>1r [ c – cost incurred, b – benefit enjoyed, r – relatedness] * Dawkins – Selfish gene (1976) – Organisms are mere epiphenomena of Evolution; real competition is at gene level - Gene’s Eye view. * Hence (for example) Altruism takes place based on the fact that the net effect of the trait (Altruism) leads to increase in frequency of underlying gene. * Since gene is the real unit of selection other levels of selection are incompatible with it, and hence a fallacy.
A Change of Mind – * Dawkins and
The Units and Levels of Selection by Samir Okasha (Ch 8, A Companion to Philosophy of Biology)
Traditional Darwinian View – * Though Darwin treats individual organisms as basic unit of selection, other possibilities can be seen * Lewontin (1970) – Natural Selection will operate on any level that exhibits ‘heritable variation in fitness’. * Hence the question of level seems purely empirical – but is not.
Historically – * The debate of Levels of Selection can be traced back to Darwin himself – Descent of Man (1871) – tries to explain ‘altruist behaviour’ based on selection at group level. * Weismann has also shown a similar thinking of hierarchical levels of selection. * G. C. Williams in Adaptation and Natural selection (1966) attacked the idea of group selection regarding it to be a weak evolutionary force as compared to individual selection – Pointed out that only a concept of between-group selection can be an evolutionary force * Hamilton – Kin Selection * Hamilton and Williams – ‘Gene’s eye view’ – Popularised by Dawkins (1976)
The Gene’s Eye View – * Hamilton – Altruistic behaviour towards related organisms. Relatives share same genes, hence the beneficiary of the act will be carrying same gene as the actor – Kin selection. * Hamilton’s rule – Altruism favoured by selection as long as cost incurred by the altruist is offset by sufficient amount of benefit to a related organism. bc>1r [ c – cost incurred, b – benefit enjoyed, r – relatedness] * Dawkins – Selfish gene (1976) – Organisms are mere epiphenomena of Evolution; real competition is at gene level - Gene’s Eye view. * Hence (for example) Altruism takes place based on the fact that the net effect of the trait (Altruism) leads to increase in frequency of underlying gene. * Since gene is the real unit of selection other levels of selection are incompatible with it, and hence a fallacy.
A Change of Mind – * Dawkins and