During the eighteenth, nineteenth, and early twentieth centuries, scientific inventories of biodiversity flourished as naturalists participated in expeditions throughout different geographic regions of the world (Köhler et al. 2005). These expeditions and the various journals produced by many prominent naturalists provided materials for extensive scientific collections as well as accounts of the habits and habitats of both plant and animal species. Charles Darwin and Alfred Russel Wallace were part of this tradition, and both were students of biodiversity. They chronicled their adventures in South America, the Malay Archipelago, the Galapagos Islands, New Zealand, and Australia as they discovered new species, described geology, and encountered various cultures (Darwin 1845; Wallace 1869). These adventures honed their observational skills, and their experiences culminated in their parallel proposals of the theory of biological evolution by means of natural selection. The biodiversity and natural environments encountered by Darwin and Wallace have been altered, and both habitats and species described in their journals have and are being impacted at a drastic rate. The yellow-bridled finch (Melanodera xanthogramma), noted by Darwin as “common” in the Falkland Islands, is now gone, and, as predicted by Darwin, the Falkland Islands fox or warrah (Dusicyon australis) went extinct in 1876 (Armstrong 1994). The Borneo forest harbors fewer Mias or orangutans, and it is unlikely that one would be allowed to collect specimens like Wallace describes (Wallace 1869). Even “pristine” regions, such as those seen by Darwin in Patagonia and the southwest Atlantic coast of Argentina, are still poorly understood, yet they are threatened by numerous human activities (Bortolus & Schwindt 2007).

It is clear that scientific studies that investigate the influence of environmental pollutants on evolutionary processes are applicable to all species. The discussion here, however, deals with organisms other than humans, and it recognizes, of course, that distinctions, at the molecular level, between toxic effects to humans and to other species often are not discretely distinguishable. The important distinction to be made here is that studies of the effects of environmental contaminants on human health are ultimately concerned with the health of individuals, whereas studies that deal with natural populations of wildlife or other organisms focus on the well-being of populations.

Evolutionary toxicology is the study of the effects of pollutants on the genetics of natural populations (Bickham & Smolen 1994; Bickham et al. 2000; Matson et al. 2006). The emergence of evolutionary toxicology as a new field of scientific investigation was noted in the early 1990s at the Napa Conference on Genetic and Molecular Ecotoxicology held at Yountville, California, in October 1993 (Bickham & Smolen 1994). The stated goal of this new endeavor was to identify environmental pollutants that influence evolutionary processes and to quantify the extent of their effects. The procedures and techniques of modern molecular biology to population genetics were invoked to accomplish this goal.

Evolution includes the change in inherited traits of a population from one generation to the next. Natural factors that drive genetic diversity are gene flow, mutation, natural selection, bottlenecks, and genetic drift (Belfiore & Anderson 2001; Staton et al. 2001). Mutations to genes are changes in the nucleotide sequence of an organism’s genetic material that can produce new or altered traits in individuals. These changes, in turn, can produce disease, illness, or susceptibility in numerous ways. Gene flow as a result of interactions with immigrating individuals into a population can cause a variety of effects, including increased genetic diversity, homogenization of genetic patterns across populations, and even hybridization among species. Mutations may be spontaneous or induced by exposure to genotoxins (i.e., ultraviolet and high-energy radiation or certain chemicals).

The world would be a wonderful place if our natural resources (e.g., forests, fish, and wildlife) needed no management and conservation was not a concern. In a world with a global human population approaching 7 billion and where most developed nations overconsume these resources, however, conservation is a concern and management is necessary for sustainable use. Historically, natural resource management strategies were determined by the collection and interpretation of basic field data. Today, as challenges to the sustainability and conservation of our natural resources arise, managers often need data that cannot be acquired using conventional methods. For example, a natural resource manager might want to know the number of successful breeders in a population or if genetic variation was being depleted because of a management practice. Traditional field craft alone cannot directly address such questions, but the answers can be determined with some precision if the field work is coupled with modern molecular genetic techniques.

Molecules can enlighten us about biological attributes that are virtually impossible to observe in the field (Avise 2004). Parentage analysis is one such arena in which genetic data can inform management practices (DeWoody 2005), but there are a host of others. For example, molecular data have revealed deep evolutionary splits in stocks at one time thought to be homogeneous. This finding has concomitant management implications (Hoffman et al. 2006). Similarly, molecules can enlighten us about biologies that are virtually impossible to observe in the field, such as pollen flow (Hamrick, this volume) or the physiology of migration (Nichols et al. 2008).