  This paper proposes a model to explain the potential role of inter-group
conflicts in determining the rise and fall of signaling norms. Individuals in a
population are characterized by high and low productivity types and they are
matched in pairs to form social relationships such as mating or foraging
relationships. In each relationship, an individual's payoff is increasing in
its own type and its partner's type. Hence, the payoff structure of a
relationship does not resemble a dilemma situation. Assume that types are not
observable. In one population, assortative matching according to types is
sustained by signaling. In the other population, individuals do not signal and
they are randomly matched. Types evolve within each population. At the same
time, the two populations may engage in conflicts. Due to assortative matching,
high types grow faster in the population with signaling, yet they bear the cost
of signaling, which lowers their population's fitness in the long run. Through
simulations, we show that the survival of the signaling population depends
crucially on the timing and the efficiency of weapon used in inter-group
conflicts.
