Evolutionär stabile Strategien

Aus Dawkins, Das egoistische Gen, S. 69

The essential concept Maynard Smith introduces is that of the evolutionarily stable strategy, an idea that he traces back to W. D. Hamilton and R. H. MacArthur. A ’strategy‘ is a pre-programmed behavioural policy. An example of a strategy is: ‚Attack opponent; if he flees pursue him; if he retaliates run away.‘ It is important to realize that we are not thinking of the strategy as being consciously worked out by the individual. Remember that we are picturing the animal as a robot survival machine with a pre-programmed computer controlling the muscles. To write the strategy out as a set of simple instructions in English is just a convenient way for us to think about it. By some unspecified mechanism, the animal behaves as if he were following these instructions.

An evolutionarily stable strategy or ESS is defined as a strategy which, if most members of a population adopt it, cannot be bettered by an alternative strategy.* It is a subtle and important idea. Another way of putting it is to say that the best strategy for an individual depends on what the majority of the population are doing. Since the rest of the population consists of individuals, each one trying to maximize his own success, the only strategy that persists will be one which, once evolved, cannot be bettered by any deviant individual. Following a major environmental change there may be a brief period of evolutionary instability, perhaps even oscillation in the population. But once an ESS is achieved it will stay: selection will penalize deviation from it.

Ich denke, dass Überlegungen zu einer stabilen Strategie viel dazu beitragen können, evolutionäre Lösungen zu entwickeln und andere auszuschließen. Es zeigt auch noch einmal, dass Gruppenselektion häufig genau hieran scheitert: Es ist keine stabile Strategie, weil diejenige, die für die Gemeinschaft arbeiten leicht ausgenutzt werden können.