The African antelopes promise the most comprehensive evolutionary studies in large mammals. Antelopes include more living and extinct species than does any other large mammal group known over the past 20 million years. Their fossil record is exceptional not only in terms of species-richness, but also in the wealth of dating estimates and paleoenvironmental data associated with it. Vrba and DeSalle are analyzing the phylogenetic relationship trees of three major antelope groups with abundant living and fossil representatives, by studying DNA molecules of living species, and skull characters of living and extinct species. DNA changes between pairs of species will be compared with absolute dates for the same lineages in the fossil record. This will allow 1) estimates of rates of molecular change in lineages and 2) estimates of absolute dates of the origins of new species by lineage-branching; and 3) comparison of nature of these evolutionary events with the nature of coincident paleoenvironmental changes. The powerful compound data set will test various, hypotheses of how evolution occurs. One such hypothesis whether there is synchronization across phylogenies of speciations (predicted if wide-spread climatic changes provide the common driving force that initiates evolutionary changes in many lineages) versus random distribution against time. The Family of humans, Hominidae, evolved over the same time period and African areas. In fact, by far the most abundant large mammal fossils found together with early hominid remains are the very antelope groups under study. Thus, the nature and timing of evolutionary responses in hominids will be compared with those of the co-evolving large mammal lineages. A comprehension of the rich physical and biological context of human evolution is necessary for understanding human origins.
