Fig 1.
a: Demes begin a generation with given technology and number of SI types. b: Interaction during a generation gives individual fitnesses and causes advances in deme technology (here, demes A and C increase their tech level). c: Some demes (here, deme B) face invasion by other demes (deme A). If the invading deme has higher technology, the invaded deme is eliminated and replaced by a replica of the invading deme (here, deme B is eliminated and replaced by deme D, a replica of deme A). d: Demes reproduce and populate the next generation via a finite population replicator dynamic (here, we see within-deme selection and genetic drift in demes A and D changing the number of SI types). e: Technology levels and number of SI types are carried forward into the next generation.
Table 1.
Payoffs to within-deme interactions, when the deme has current technology level τ.
ατ > 1. Entries are interaction-payoffs of an individual whose strategy is given by the row when interacting with an individual whose strategy is given by the column.
Fig 2.
The effect of shared intentionality on technology dynamics.
Blue-colored vertices represent individuals playing ‘new’, white vertices represent individuals playing ‘old’. Individuals not shown are assumed to be playing ‘old’. a: In the absence of SI, the only better response for any individual is to retain his current strategy. b: For low α, coalitions of SI type individuals can coordinate payoff improving switches back to ‘old’. c: For high α, coalitions of SI type individuals can coordinate payoff improving switches to ‘new’ [14]. Note that threshold values of α depend on graph structure and that different interaction structures can yield different thresholds [14, 46]. For an example with explicitly calculated thresholds, see Section S2.2.
Fig 3.
Demes with given fraction of SI type individuals and technology level per generation under benchmark conditions.
a: α = 1.2, starting from a state in which each individual is SI or N type with equal probability, b: α = 2.2, starting from a state in which no individuals are SI type. Arrows indicate where demes rich in N and SI types respectively gain a technological advantage.
Fig 4.
The dramatic switch to a high SI, high technological change, phase for sufficiently high α.
Starting with each individual equiprobably SI or N type under benchmark conditions, a: Mean and standard deviation of fraction of SI type individuals across all 64 demes and 10 replicates during generations 451 to 500, b: Average rates of technological change (steps per generation) across all 64 demes and 10 replicates over generations 451 to 500.
Table 2.
Benchmark values are in bold.