Theory 59/Population/Sex allocation
Sex Ratio Follows Investment
The claim
Population sex ratio is set by the ratio of investment in sons to investment in daughters, so species with dimorphic costs produce the rarer sex more cheaply.
01Mechanism
Frequency-dependent selection equalises return per unit investment, not numbers; the ratio sets the equilibrium.
02Prediction
Sex ratio should track investment ratios.
03Refutation
Sex ratio tracking chromosome mechanism would remove investment.