With National Science Foundation support Dr. Fisher will study tusk dentin laminations in a series of mammoths and mastodonts which lived between ca. 12,000 and 10,000 years ago in North America. Prior work by Dr. Fisher has shown that the tusks and cheek teeth of these species exhibit dentinal laminations that record details of individual life history. Successive orders of lamination represent annual, fortnightly and daily cycles in accreted dentin. Analyses of these patterns yield data on seasonal mortality, age, sex, growth rates, age at sexual maturity and calving. These factors are sensitive to the nature and degree of ecological stress to which the animal had been subjected and demonstrate predictable patterns of response to altered nutritional status and/or predation pressure. With such data Dr. Fisher will quantify these life history trails for the two species just before their time of extinction. He will compare the results with data from extant elephants from a range of environments. On this basis he will determine the factors which led to the extinction of mammoths and mastodonts at the end of the Pleistocene. It has long been known that the end of the last Ice Age saw the extinction of many species of animals in North America. While this fact is undisputed the cause has yet to be determined. While some scientists argue that environmental change alone is responsible, others note that these major extinctions seem to coincide with the appearance of human hunter gathers in North America and believe that overhunting led to their demise. The data Dr. Fisher will collect allows, he believes, for a distinction between these possible causes. This research is important for several reasons. It will provide paleoanthropologists with insight into prehistoric human behavior and subsistence patterns. It will also shed light on the relationships between human predation, environmental exchange and species extinction, a problem of major significance today.
