32

4

Evolution

Fig. 4.1 Sketch of

speciation according to the

punctuated equilibrium

concept

4.1.1

Group and Kin Selection

This topic arose through attempts to encompass altruism ⁹ in evolutionary theory:

an apparent paradox arises because the individual cost of altruism suggests that it

should always be selected against (selection being considered to operate at the level

of the individual). ¹⁰ The concepts of group selection and kin selection arose through

attempts to incorporate the emergence of social behaviour into evolutionary theory.

One posits a social structure in which individuals form clusters (cf. Sect. 13.2) or

groups; a group exists if its members interact much more frequently with each other

than with members of other groups. It is then asserted that natural selection operates at

the level of the group. To avoid any implicit restriction to a single level of clustering,

group selection is better referred to as multilevel selection. On the other hand, the

concept of inclusive fitness (often referred to as kin selection) appears to deliver a

similar result.

Let the donor be the executor of some altruistic act of kindness, and the acceptor

the beneficiary. IfGerman upper RR is the genetic relatedness (given, for example, by Sewall Wright’s

coefficient of relationship) between donor and acceptor, German upper BB the benefit (in terms of

fitness) to the acceptor, and German upper CC the fitness cost to the donor, then Hamilton’s rule ¹¹

(drawing on the Price equation ¹²) states that altruism will be favoured if

German upper R upper B greater than German upper C periodRB > C .

(4.1)

9 West et al. (2006).

10 McAndrew (2002); albeit that pleiotropy stabilizes (Foster et al. 2004).

11 Hamilton (1964).

12 Price (1970), Gardner (2020).