2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/133122The distribution of age-ordered frequencies arising from an exchangeable Gibbs partition is studied in relation with the distribution of the positions at which new mutations appear in a sample.Resubmitted version, converse to main proposition proved, most proofs improved, misleading section in the introduction removedProbabilityStatistics Theorytext