Dissertations in biological anthropology need to look both backward into history and forward into the future of research possibilities. Your first challenge when choosing a topic will be to find one on which no Ph.D. candidate has previously written. But as The British Association for Biological Anthropology (BABAO) points out, this is a field that studies a range of fascinating topics in areas like human evolution, primatology, human genetics, evolutionary medicine and human behavioral ecology.
One area of study that will offer a wealth of topics is evolutionary biology. Research that applies evolutionary perspectives to a phenomenon like socioendocrinology (the study of the relationship between social behavior and behavior as dictated or influenced by hormones) will prove insightful and important in the field. Other studies could include surveys of specific cultures that are faced with indigenous diseases. You could also pursue a topic that has a popular culture bent, such as a study of the evolutionary perspectives of morning sickness or vegetarianism. Other cutting-edge research currently being pursued includes ascertaining ancestry from studying the femur or looking at dogs as models for human evolution; topics that continue these studies would be valuable.
Cultural or Geographical
Topics that border more on the soft sciences would include dissertations that take a cultural or geographical angle. For example, you could look at specific geographic areas of the world to see how certain phenomena affect them. One good example would be examining chimpanzee conservation in areas where mining is important. Other topics would include research into the ecological knowledge of geographically and culturally isolated fishermen, or studies of food as a cultural institution in indigenous cultures, or the influence of ethnic cultures in urban areas (like Miami or San Antonio) where they are known to have a huge impact.
Some anthropological dissertation will be attractive to Ph.D. students who want to study animal life. This type of research would look at a culture as a gestalt principle or a whole, taking into account the symbiotic relationships of plants, animals and humans. Topics in this area would include very straightforward studies of the biomechanical or communicative utterance similarities of primates and humans, or environmental impact studies that look at the effects of ranching (a human activity) on a specific animal community in a specific geographic area. Other topics could include a conservationist perspective in studies of animal populations like Atlantic or Pacific sharks or Amazonian wild squirrel monkeys.
Finally, dissertations that examine the relationship between human and plant life add great value to the field of anthropology, as well as tangential fields like biology and environmental studies. For example, dissertations can research the efficacy of genetically modified rice as a method to end hunger, particularly if these studies take an evolutionary perspective. Other topics along these lines would include social movements and scientific forestry, or effects of forest fragmentation (when forests get carved up either by natural or man-made means), the role of the local food movement in farming in certain parts of the United States, or even the efficacy of introducing ethnobotany into third world cultures.