Population Parameters
×10⁻⁴
Evolution Mode
Molecular Clock
generations per frame
Kimura's Neutral Theory (1968):
Most molecular variation is selectively neutral. The substitution rate K equals the mutation rate u, independent of population size. This creates a "molecular clock" for dating evolutionary events.
Most molecular variation is selectively neutral. The substitution rate K equals the mutation rate u, independent of population size. This creates a "molecular clock" for dating evolutionary events.
Substitution Accumulation (Molecular Clock)
Observed Substitutions
Expected (K=u)
Selection Prediction
Heterozygosity Over Time
Observed H
Expected H = 4Nu/(1+4Nu)
Allele Frequency Spectrum
Generation
0
Total Substitutions
0
Observed Rate (K)
0.000
Expected Rate (u)
0.001
Heterozygosity
0.000
Variance/Mean Ratio
1.00
Neutral Theory Predictions
• Substitution rate K = u (mutation rate)
• Independent of population size N
• Variance/Mean ratio ≈ 1 (Poisson)
• Constant molecular clock
Selectionist Predictions
• Substitution rate depends on s and N
• K = 2Ns × u for beneficial mutations
• Variance/Mean > 1 (overdispersed)
• Variable molecular clock