The genetical theory of kin selection

Abstract

Natural selection operates both directly, via the impact of a trait upon the individual’s own fitness, and indirectly, via the impact of the trait upon the fitness of the individual’s genetically related social partners. These effects are often framed in terms of Hamilton’s rule, rb − c > 0, which provides the central result of social‐evolution theory. However, a number of studies have questioned the generality of Hamilton’s rule, suggesting that it requires restrictive assumptions. Here, we use Fisher’s genetical paradigm to demonstrate the generality of Hamilton’s rule and to clarify links between different studies. We show that confusion has arisen owing to researchers misidentifying model parameters with the b and c terms in Hamilton’s rule, and misidentifying measures of genotypic similarity or genealogical relationship with the coefficient of genetic relatedness, r. More generally, we emphasize the need to distinguish between general kin‐selection theory that forms the foundations of social evolution, and streamlined kin‐selection methodology that is used to solve specific problems.

Monogamy and haplodiploidy act in synergy to promote the evolution of eusociality

“…A role of synergy in kin selection has been recognized before 22,[26][27][28] , but its interaction with demographic and genetic processes that assort cooperators together has not been fully recognized. Synergy arises when joint efforts achieve more than the sum of their parts.…”

Hamiltonian inclusive fitness: a fitter fitness concept

“…To his delight, his results were derived via a very different approach by Price, who used the covariance between genetic traits and fitness [37,38] to generalize inclusive fitness theory, an advance that Hamilton found at once elegant and more informative. Price's approach showed the mathematical equivalence of Hamilton's kin-based formulation and group selection; indeed, the former proved to be simply a special case of the latter [39][40][41], differing only in the way in which the genetic variance is partitioned. This fact surprised Hamilton at first, but he soon saw the power of Price's approach, leading him to rethink the idea of group selection.…”

Queller’s Separation Condition Explained and Defended

“…Roughly speaking, an individual's breeding value with respect to a character P is a measure of its genetic predisposition to express P . More precisely, it is its value for that character as predicted by a linear combination of its allelic values, weighted by their average effects on the character (Falconer and Mackay 1996;Frank 1998;Gardner et al 2011).…”

“…From an inclusive fitness perspective, the genes for a social behaviour spread because they contribute to the inclusive fitness of their bearers: that is, they make a positive contribution to the actor's genetic representation in future generations (Hamilton 1964(Hamilton , 1970Gardner et al 2011). From a multi-level selection (or group selection) perspective, the evolution of social behaviour results from the interplay of selection within groups and selection between groups (Price 1972;Wilson 1975;Okasha 2006).…”

“…Both approaches typically begin with a partition of the Price equation (Price 1970(Price , 1972. In the inclusive fitness partition, we split the change attributable to selection into components separately attributable to the direct and indirect fitness effects of the social behaviour under consideration (Queller 1992a;Gardner et al 2011). In the multi-level partition, we split the change into components separately attributable to selection within groups and selection between groups (Price 1972;Wade 1985;Okasha 2006).…”