VERTEBRATE STUDIES | Speciation and Evolutionary Trends in Quaternary Vertebrates
The Quaternary is an ideal interval in which to study the origin of vertebrate species and their adaptations in the fossil record. The time intervals available (10 2 –10 6 years) are of the order of magnitude at which such processes occur; there is a rich fossil record over a wide geographical area; and paleoenvironmental and dating studies allow us to put the evolving vertebrates into a chronological and ecological context. This article focuses on case histories of phenotypic evolution that can be traced through stratified sequences of fossils. Speciation can be seen in bears (origin of cave bear and polar bear), while adaptive transitions within and across species are seen in various lineages of rodents and in mammoths. A multiplicity of evolutionary modes is evident. Whether evolution accelerated in the Quaternary is still an open question. The integration of morphological and molecular studies offers particular potential for the future.