Endemic African mammals shake the phylogenetic tree

The order Insectivora, including living taxa (lipotyphlans) and archaic fossil forms, is central to the question of higher-level relationships among placental mammals(1). Beginning with Huxley(2), it has been argued that insectivores retain many primitive features and are closer to the ancestral stock of mammals than are other living groups(3). Nevertheless, cladistic analysis suggests that living insectivores, at least, are united by derived anatomical features(4). Here we analyse DNA sequences from three mitochondrial genes and two nuclear genes to examine relationships of insectivores to other mammals. The representative insectivores are not monophyletic in any of our analyses. Rather, golden moles are included in a clade that contains hyraxes, manatees, elephants, elephant shrews and aardvarks. Members of this group are of presumed African origin(5,6). This implies that there was an extensive African radiation from a single common ancestor that gave rise to ecologically divergent adaptive types. 12S ribosomal RNA transversions suggest that the base of this radiation occurred during Africa's window of isolation in the Cretaceous period before land connections were developed with Europe in the early Cenozoic era.