The social science of anthropology is conventionally divided into four major sub-fields, each of which has different theoretical frameworks and methodologies from the others: social anthropology and cultural anthropology; archaeology; biological anthropology and physical anthropology; and linguistic anthropology. Overall, anthropology bills itself as the study of human culture and humanity; therefore, each of these sub-fields is a major way of approaching the broader research subject.
Cultural anthropologists study the differences among various human cultures, through methods such as interviews and field-work observations. It is this area of work which characterized most early anthropology (or "ethnology"), such as the work of Edward Tylor, James Frazer, and Franz Boas. Many of the biases which informed this earlier work, such as notions of primitiveness and "civilization," have since been discarded, at least in theory.
This field of research ultimately arose from the attempt to explain similarities and differences across human cultures: for example, did cultural practices spread gradually across all cultures (explaining similarities), or were they invented multiple times, independently? This originally led to the classical formulation of stages of social progress (from primitives to civilizations), but this has now been largely rejected, via the twin insights that so-called "primitive" societies actually have extreme social complexity, and that many societies both skip supposedly essential "stages" on their way forward, and sometimes seem to regress "backwards."
Today, the focus of cultural anthropology or ethnology is generally to understand how people in different societies perceive themselves and perceive the world around them, particularly through art and stories (including legends and myths), and social institutions such as families (kinship) and leadership structures.
Archaeoologists study the material remains of past cultures, attempting to reconstruct an understanding of these past societies through what they have left behind. (Note that archaeologists reconstruct past cultures through material remains, whereas historians reconstruct them through written records.) The classical fieldwork of archaeologists is the location, excavation, and removal of artifacts from dig sites.
Given this focus, the archaeology sub-field has its roots in the search for relics of the past during the 17th through the 19th centuries, such as the collection of Egyptian artifacts by European scholars under the banners of Oriental studies. Archaeologists can be found studying past and especially extinct human cultures all over the world: Ancient Egypt and other ancient Mediterranean cultures (including the Greek and Roman empires), ancient China, ancient Mesoamerican cultures (such as the Incas, Mayans, and Aztecs), and former community and burial sites of Native peoples in the United States and Canada.
Biological anthropology or physical anthropology studies specific components of the evolutionary process, human genetics and adaptation, and the human fossil record. Note that this is technically separate from archaeology, although both will often find themselves working with remains of the deceased and of extinct cultures. The practices of physical anthropology actually predate the rise of the theory of evolution in the work of Charles Darwin and Gregor Mendel, but the field happily incorporated evolution in order to broaden its research agenda.
Today biological anthropology is actually an extremely diverse field. Biological anthropologists can be found studying primates, close human relatives such as gorillas and chimpanzees (primatologists); the medical and physical consequences of current-day problems of pollution and nutrition (human biology and biomedical anthropology); the history of the evolution of the human species (both in terms of fossil evidence, or paleoanthropology, and the evolution of social behaviour, or behavioural ecology); and the specific evolution of the brain (neuroanthropology), generally regarded as the most unique and complex organ in the human body.
A second branch of specialization in biological anthropology involves the study of skeletal remains (osteology). This field is home to forensic anthropologists, specialists who examine human remains to assist police and medical examiners (or coroners) in identifying causes of death and analyzing evidence for criminal prosecutions.
Linguistic anthropologists study their subject through the theories and methods of linguistics and semiotics. This originally emerged, during the twentieth century, from the study, analysis, and classification of languages throughout the world, with a particular focus on those at greatest risk of dying out - typically, indigenous languages in places subject to rapid assimilation, like the aboriginal populations of North America and the South Pacific islands.
Whereas the first generation of linguistic anthropologists focussed on the objective classification of different languages, the next generation of critical social theorists, in the 1960s and 1970s, concentrated instead on the social construction of all language. Led by Dell Hymes, these anthropologists explored speech rather than language - that is, the social context of particular instances of communication, rather than the objective existence of language outside of these social situations. Since the 1980s, this turn toward social construction has continued through the development of new methods of analysis examining ways in which language constitutes, or creates, broader social identity and perceptions of reality.