ABSTRACT
In the study of evolution, including that of humans from ancestral primates, it has been traditional to begin with forms living in a remote period of the past and end with modem human beings (Valentine, 1978). This procedure has seemed logical, especially as the evolutionary sequences were arrangements determined by fossil evidence. In the early part of the 19th century it was the uncertainties about these orderings that formed major scientific barriers to the acceptance of theories of evolution (Ruse, 1979). It has also been customary to make comparisons among living and extinct forms according to a sequence suggested by the great chain of being, which, in the vertebrates, ran from fish to amphibians to reptiles to birds, and finally to mammals. Because the living representatives of these great groups do not constitute an evolutionary sequence, the problems that arise when one acts as though they did, are much greater than is usually realized (Hodos, 1970). Most students of evolution today enrich their understanding of fossils by studying living descendants, a method used by the late A. S. Romer and clearly illustrated in The Vertebrate Story (1959).
