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Abstract

Adaptations are often spoken of as ‘for the good of’ some entity, but what is that entity? Groups and species are now rightly unfashionable, so what are we left with? The prevailing answer is Darwin's: ‘the individual’. Individuals clearly do not maximise their own survival so the concept of fitness had to be invented. If fitness is correctly defined in Hamilton's way as ‘inclusive fitness’ it ceases to matter whether we speak of individuals maximising their inclusive fitness or of genes maximising their survival. The two formulations are mutually inter-translatable. Yet some serious mistranslations are quoted from the literature, which have led their authors into actual biological error. The present paper blames the prevailing concentration on the individual for these errors, and advocates a reversion to the replicator as the proper focus of evolutionary attention. A gene is an obvious replicator, but there are others, and the general properties of replicators are discussed. Defenders of the individual as the unit of selection often point to the unity and integration of the genome as expressed phenotypically. This paper ends by attacking even this assumption, not by a reductionist fragmentation of the phenotype, but, on the contrary, by extending it to include more than one individual. Replicators survive by virtue of their effects on the world, and these effects are not restricted to one individual body but constitute a wider ‘extended phenotype’.