Facilitated Variation: How Evolution Learns from Past Environments To Generalize to New Environments
Figure 6
Adaptation towards novel modular goals is more rapid in MVG organisms.
(A) An example of new-comb goal in the RNA model, where the new goal structure is composed of previously seen sub-structures but in new combinations. (B) Maximal normalized fitness in RNA populations (mean±SE) as a function of generations for new-comb structures. The x-axis is generations, where zero is the point where the goal changes to a new-comb structure. Initial populations are FG-populations evolved toward G1 and MVG populations taken from the end of the last G1-epoch. Data are from 15 simulations for the four new-comb goals of (A). Inset: competition of FG and MVG populations under a new-comb goal (following the method of [44]). Initial populations were composed of equal fractions of FG-populations and MVG populations. Data are from 30 competition runs for each of the four new-comb goals. (C) Novel-module goal in the logic circuit model. In the novel-module goal, one of the 2 XORs or the OR operation was changed into a different 2-inputs Boolean function such as AND, NOR or XOR, not seen in the history of the evolution. (D) Maximal normalized fitness (mean±SE) as a function of generations for novel-module goals in the logic circuit model. At time zero the goal changes to a novel-module goal. Initial populations are as in (B). Data are from 30 simulations in each scenario, for 20 different novel-module goals (listed in Text S1 section 6.4.2). Inset: Competition of FG and MVG organisms in a novel-module environment. Starting populations were composed of equal fractions of FG and MVG populations. Data are from 30 simulations for 20 novel-module goals. (E) Same as in (D) but for non-MVG language goals. Here, the goal is a randomly chosen Boolean function, generated by randomly generating a 4-input 1-output truth table. Goals with a difficulty level similar to that of (D) were chosen, as evaluated (Text S1 section 6.2). Data are for 35 non-MVG language goals. Inset: Competition results as in the inset of (D).