Nature 2006:
One of the greatest challenges in the modern biological and social
sciences is to understand the evolution of cooperative behaviour.
General outlines of the answer to this puzzle are currently
emerging as a result of developments in the theories of kin
selection1–7, reciprocity8–10, multilevel selection11–15 and cultural
group selection16,17. The main conceptual tool used in probing the
logical coherence of proposed explanations has been game theory,
including both analytical models and agent-based simulations6,7,9,18–
24. The game-theoretic approach yields clear-cut results
but assumes, as a rule, a simple structure of payoffs and a small set
of possible strategies. Here we propose a more stringent test of the
theory by developing a computer model with a considerably
extended spectrum of possible strategies. In our model, agents
are endowed with a limited set of receptors, a set of elementary
actions and a neural net in between. Behavioural strategies are not
predetermined; instead, the process of evolution constructs and
reconstructs them from elementary actions. Two new strategies of
cooperative attack and defence emerge in simulations, as well as
the well-known dove, hawk and bourgeois strategies. Our results
indicate that cooperative strategies can evolve even under such
minimalist assumptions, provided that agents are capable of
perceiving heritable external markers of other agents.