Sudden replacement of cave bear mitochondrial DNA in the late Pleistocene.

In the absence of interaction with genetically distinct populations, changes in frequencies of distinct mitochondrial DNA (mtDNA) sequences (haplotypes) within a population are caused by mutations and genetic drift, both of which are comparatively slow processes. By contrast, interactions between populations may lead to rapid changes in haplotype frequencies [1–3], for instance through extinction and recolonialisation. So far, the only case of a direct replacement of mtDNA sequences within a continuous population has been described in historical mouse populations [2].