Chapter Chapter-by-Chapter Anaylsis of The Selfish Gene (1989 edition) - Study Guide by Richard Dawkins

injure and kill their opponent, continuing until the opponent retreats or one of the combatants is seriously injured, though in the process they will risk injury themselves. Doves simply threaten and never engage in serious fights and will retreat when attacked. In this evolutionary game, let the winner of a contest score +50 and the loser 0. The cost of a serious injury is –100 and the cost of wasting time in threatening is –10. Now consider the possible types of encounters in this game. Hawks always beat Doves (because the dove runs away) but if they fight another hawk, they stand equal chance of winning or being injured. If two Doves fight, each has an equal probability of winning; neither is injured but they both spend a lot of time threatening.

For the purpose of this book, we are not interested in whether hawks will tend to beat doves when they fight – we already know that hawks will always win. What is important is whether either of these strategies are evolutionary stable strategies. As we can see, neither of these two strategies would be an ESS. If all individuals in a population are doves, every contest is between a dove and another dove and the payoff is on average +15 (winner = +40, loser = -10. Probability of winning = ½. Average payoff = ½(40-10) = +15). In this population, any mutant hawk would do very well (+50) and the Hawk strategy would soon spread. Likewise, in a population of all hawks, the average payoff is –25 (½(50-100) = -25) so any mutant dove would do better because when a Dove meets a hawk, it gets 0. Therefore, the Dove strategy would spread if the population consisted mainly of hawks.

Thus, it can be seen that both strategies, if present in their pure form, are vulnerable to invasion by the other strategy. The stable equilibrium occurs when the average pay-offs for a hawk are equal to the average pay-offs for a dove. For the particular arbitrary points system that we are using in this example, the stable ratio in a population turns out to be 5/12 doves and 7/12 hawks. However, in practice, individuals do not play either one strategy or the other. Instead every individual is capable of behaving either like a hawk or like a dove in each particular contest and the ESS is achieved when the probability of an individual behaving like a hawk is 7/12 and the probability of them behaving like a dove is 5/12.

However, hawk and doves are not the only possible strategies to adopt, there are alternative strategies called Retaliator, Bully, and Prober-retaliator. Likewise, the Hawk-Dove scenario described above is an example of a symmetric contest, where we have assumed that the contestants are identical in all respects except their fighting strategy. There are in fact several asymmetries, such as individuals differing in size and fighting ability, which will all "be taken into account" when an individual "chooses" what strategy to adopt.

Therefore, depending on the relative costs and benefits of aggressive behaviour, an individual will choose from the broad range of different fighting strategies, or indeed play a complex mixture of several, that will maximise his net benefit for his genes.

Genemanship

A selfish gene is not just one single physical bit of DNA. It is all replicas of a particular bit of DNA whose aim is to get more numerous in the gene pool. Not only could it do this by reproducing itself so that it’s offspring carried it’s genes into the next generation, it could also do this by assisting replicas that are sitting in other bodies. Therefore, Dawkins suggests that individual altruism is in fact brought about by gene selfishness.

However, to be able to do this, the gene must be able to "recognise" their copies in other individuals. Theoretically, it is possible that a gene could arise which produced an external, visible label and, at the same time, a tendency to be nice to other bearers of that label. Dawkins called this idea the Green Beard Altruism effect which, although unlikely, proposes that one and the same gene produces a green beard and a fondness for other green beards.

Another, more plausible, way of recognising their copies is in close relatives, who have a greater than average chance of sharing the same genes. It is widely accepted that this must be why altruism by parents towards their young is so common, but the same applies for other close relatives such as brothers,