A while ago I pointed out a discussion in R. A. Fisher’s Genetical Theory of Natural Selection which showed a pretty clear understanding of the concept of inclusive fitness, and shortly after that I mentioned a passage in his published correspondence that seemed equally clear.
While consulting GTNS for another purpose I have noticed another small example. In his section on ‘reproductive value’ Fisher considers how the ‘direct’ reproductive value of a woman, measured by the ‘present value of their future offspring’ will vary with age, increasing as the child passes through the dangers of high infant and child mortality, reaching a peak in early adulthood, then declining as the years of childbearing go by, and reaching zero around age 50 with the end of reproduction. But Fisher adds in passing that ‘the reproductive value of an older woman… is undervalued [in Fisher’s calculations] in so far as her relations profit by her earnings or domestic assistance’ [p.29]. The use of the term ‘relations’ rather than ‘children’ implies recognition of one of the essential points of inclusive fitness, that the evolutionary ‘value’ of an individual includes their contributions to the reproduction of close genetic relatives (not necessarily offspring).
Altogether in GTNS Fisher gives at least seven examples of inclusive fitness:
1. Suckling of children [27]
2. The help a post-reproductive mother gives to her children [27]
3. The inhibiting effect of a foetus or baby on further conception [27]
4. The services of neuter insects to their queen [27]
5. The services of post-reproductive women to their ‘relations’ [29]
6. The protective effect of distastefulness on the siblings of gregarious insect larvae [159]
7. The evolution of reproductive specialisation in social insects [186].
While of course the main credit for developing the theory of inclusive fitness should still go to W. D. Hamilton, Fisher’s various comments show that he had more than an inkling of the theory.
All page references are to R. A. Fisher: Genetical Theory of Natural Selection: a complete variorum edition, ed. Henry Bennett, 1999.
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