Mammoths, molecules and morphology: A case study in ancient speciation

Abstract

Recent research on ancient DNA back to a million years or more has contributed significantly to our understanding of mammalian evolution. We focus on mammoths, the most intensively studied lineage after humans. Recent genomic data confirm the model, originally based on morphology, that Early Pleistocene mammoths from northeast Siberia, of relatively advanced morphology, were the source of endemic North American mammoth species and the Holarctic woolly mammoth. The new data further reveal at least two introgression events in the origin of the Late Pleistocene North American mammoth, resulting from hybridisation between the endemic North American form and later immigrating woolly mammoth populations. This exemplar highlights broader implications for the reconciliation of molecular and morphological data in palaeontology. These include the detection of non-bifurcating phylogenetic processes such as hybrid speciation; the problem of morphologically cryptic species identified from DNA; and the issues these raise for species concepts, taxonomy and nomenclature of fossil taxa.