Theory 27/Ancient selection/Paleogenomics
Selection Is Visible in Time
Whether an allele was under selection is set by the ratio of its frequency change to the change expected under drift, so a small consistent change can be stronger evidence than a large ambiguous one.
01Mechanism
Drift produces frequency changes whose magnitude depends on population size; selection produces consistent directional change beyond that envelope.
02Prediction
Selected alleles should change faster than drift allows.
03Refutation
Frequency changes within the drift envelope would remove the selection claim.
04What makes it checkable
Ancient DNA now samples the same population at multiple time points, allowing change to be measured rather than reconstructed from modern genomes.
05Why it was not testable before
Modern genomes alone cannot separate selection from the demographic history that produced them.