E14: mating systems — monogamy vs promiscuity (mate-pool breadth)

A new analytic experiment on an orthogonal evolution-of-sex axis: not the
recombination RATE (E9) but the population's mating STRUCTURE. Agents on a
ring recombine with a second parent drawn from a window of breadth b
(b->0 monogamous/isolation-by-distance, b=1 promiscuous/panmictic), under
local selection, swept against NK ruggedness K.

Finding: the optimal mate-pool breadth SHRINKS as skills get more
entangled. Wide/promiscuous merging wins the champion on additive
landscapes (K<=3, b=0.6), but on rugged ones (K>=6) it prematurely
converges to a worse champion and an intermediate breadth (b~0.35) wins;
pure monogamy over-fragments. Throughout, promiscuity monotonically lifts
the population MEAN but destroys diversity and parallel exploration. The
design rule extends E9: merge widely for additive skills, keep
island-structured sub-populations for entangled ones — a merging-native
axis the panmixia-assuming literature lacks.

- src/knowledge/mating_system.py + experiment.py dispatch (kind: mating_system)
- configs/layer1/E14.yaml (breadth x K sweep, 20 reps, bitwise-reproducible)
- figures/plot_E14.py; results/E14/ (figure, README, manifest, resolved config)
- tests/test_mating_system.py (+5, 147 green); make layer1 wired
- folded into both papers (full + accessible) as the third §5 result

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

configs/layer1/E14.yaml

@@ -0,0 +1,34 @@
+experiment: E14
+kind: mating_system
+seed: 20260709
+n_replicates: 20
+
+# (Mating systems — monogamy vs promiscuity): a finite population of genotypes evolves on a Kauffman
+# NK landscape, recombining sexually, but the MATE-POOL BREADTH is swept. Agents sit on a ring; an
+# offspring's second parent is drawn from a window of half-width ~ breadth*N/2 around the focal parent,
+# and selection is LOCAL (offspring competes only against the incumbent at its ring position). breadth
+# -> 0 is monogamous / structured (local mating, isolation by distance); breadth = 1 is promiscuous /
+# panmictic (mate with anyone). Crossed with ruggedness K, this is the mating-system image of the E9
+# design rule. Expect: on smooth landscapes (K low) promiscuity maximises the best fitness (spread the
+# single good direction fastest); as ruggedness rises the OPTIMAL breadth SHRINKS toward an intermediate
+# value (full promiscuity prematurely converges below it); and diversity + occupied local optima are
+# monotonically destroyed by breadth at every K, most severely on rugged landscapes. Falsifier: the best
+# breadth is independent of K (no crossover), or promiscuity is best at every ruggedness.
+
+mating:
+  L: 12              # loci (genotype space 2^L)
+  N: 48              # population size (ring positions)
+  breadth: 1.0       # mate-pool breadth in [0,1] (overwritten by the sweep)
+  K: 0               # landscape ruggedness / epistasis (overwritten by the sweep)
+  recomb_rate: 0.5   # per-gap crossover rate (near-free reassortment within a mating)
+  mu: 0.003          # per-locus mutation rate
+
+generations: 60
+
+sweep:
+  - param: mating.K
+    values: [0, 3, 6, 10]
+  - param: mating.breadth
+    values: [0.03, 0.08, 0.17, 0.35, 0.6, 1.0]
+
+output: {dir: results/E14}