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The frequency of the intact Cyp6a17 + Cyp6a23 allele shifted rapidly under strong selection. (A) The frequencies of the intact allele in each of the six sampling years and an estimate of the frequency in modern populations are shown. (B) Results of an ABC analysis to infer the selection strength and starting frequency of the intact allele that best recapitulate our empirical sampling results between 1975 and 1983.
