William Siler

Bio: William Siler is an academic researcher. The author has contributed to research in topics: Gompertz function & Animal mortality. The author has an hindex of 1, co-authored 1 publications receiving 287 citations.

A Competing‐Risk Model for Animal Mortality

Abstract: A three—component competing—rick model for animal mortality is presented, in which the additive hazards include a new model, dominant during the prematurity period; a constant hazard, dominant during the period of maturity; and the conventional Gompertz hazard, dominant during senescence. A good fit of the model is obtained to survival data for a variety of species, with both laboratory and field data being represented. Interpretation of the model parameters in terms of animal adjustment to hazards is offered. See full-text article at JSTOR

The Decomposition of Time-Varying Hazard into Phases, Each Incorporating a Separate Stream of Concomitant Information

Abstract: The hazard function of time-related events, such as death or reoperation following heart valve replacement, often is time-varying in a structured fashion, as is the influence of risk factors associated with the events. A completely parametric system is presented for the decomposition of time-varying patterns of risk into additive, overlapping phases, descriptively labeled as early, constant-hazard, and late. Each phase is shaped by a different generic function of time constituting a family of nested equations and is scaled by a separate logit-linear or log-linear function of concomitant information. Model building uses maximum likelihood estimation. The resulting parametric equations permit hazard function, survivorship function, and probability estimates and their confidence limits to be portrayed and adjusted for concomitant information. These provide a comprehensive analysis of time-related events from which inferences may be drawn to improve, for example, the management of patients with valva...

Longevity Among Hunter‐ Gatherers: A Cross‐Cultural Examination

Abstract: Post-reproductive longevity is a robust feature of human life and not only a recent phenomenon caused by improvements in sanitation, public health, and medical advances. We argue for an adaptive life span of 68-78 years for modern Homo sapiens based on our analysis of mortality profiles obtained from small-scale hunter-gatherer and horticultural populations from around the world. We compare patterns of survivorship across the life span, rates of senescence, modal ages at adult death, and causes of death. We attempt to reconcile our results with those derived from paleodemographic studies that characterize prehistoric human lives as “nasty, brutish, and short,” and with observations of recent acculturation among contemporary subsistence populations. We integrate information on age-specific dependency and resource production to help explain the adaptive utility of longevity in humans from an evolutionary perspective.

Roe deer survival patterns: a comparative analysis of contrasting populations

Abstract: From two enclosed populations monitored for 13 and 11 years, time- and age-specific survival rates of roe deer were estimated in relation to age and study site by recent capture-mark-recapture methods. The two populations were very different. Roe deer in Trois Fontaines, a 1360 ha reserve in east France, faced severe winters. The size of this highly productive population was roughly constant during the study period. Conversely, in Chize, a 2660 ha reserve in west France with mild winters, roe deer showed density dependence in reproduction and body weight. As a general rule, females survived better than males, the survival rates of prime-age adults were the highest, and survival decreased after 7 years of age. Only the severe winters affected markedly the survivorship of roe deer

Demography in Archaeology

Abstract: Demography in Archaeology, first published in 2006, is a review of current theory and method in the reconstruction of populations from archaeological data. Starting with a summary of demographic concepts and methods, the book examines historical and ethnographic sources of demographic evidence before addressing the methods by which reliable demographic estimates can be made from skeletal remains, settlement evidence and modern and ancient biomolecules. Recent debates in palaeodemography are evaluated, new statistical methods for palaeodemographic reconstruction are explained, and the notion that past demographic structures and processes were substantially different from those pertaining today is critiqued. The book covers a wide span of evidence, from the evolutionary background of human demography to the influence of natural and human-induced catastrophes on population growth and survival. This is essential reading for any archaeologist or anthropologist with an interest in relating the results of field and laboratory studies to broader questions of population structure and dynamics.

Assessing the dynamics of wild populations

Abstract: Lotka's equations summarizing population dynamics can be approximated by functional models of the survivorship and reproductive curves, incorporating three stages of survival and reproduction, respectively. An abbreviated form uses a single reproductive parameter and two survival values. Survivorship and reproductive curves were fitted to data on northern fur seals (Callorhinus ursinus), domestic and feral sheep, white-tailed deer (Odocoileus virginianus), grizzly bears (Ursus arctos), African buffalo (Syncerus caffer), free-ranging horses, and fin whales (Balaenoptera physalus). Data for 10 species suggest a useful relationship between senescence parameters. A bias due to senescence may lead to serious underestimation of survival rates. Observed annual rates of increase of 18-20% for feral horses, 16% for southern fur seals (Arctocephalus gazella), and 60% for white-tailed deer are compatible with observed population parameters. 43 references, 11 figures, 3 tables.