Fig. 3.

Simulated cultural evolution with lucky leap, toolkit, and combination processes as well as environmentally mediated loss of tools. The environment switches between two possible states. In A the rate of environmental change is 0.0001 per generation, and in B it is 0.01 per generation; other parameters are the same. (A) When the environment changes infrequently, each change can initiate a large crash in the number of tools. (B) When the environment changes frequently, tools that are useful in both environments accumulate over time. Note that the y axes differ in A and B. Additional parameters are N = 100, P_lucky = 0.002, P_SpontLoss = 0, P_toolkit = 0.05, P_combine = 0.05, P_envUseful = 0.1, P_EnvLoss = 0.1.