One of the four fields of anthropology is physical, also known as biological. Within this division of anthropology is the study of the evolution of humans and biosocial variation. A possible research topic within this subdivision would be to study a specific species of hominid, such as the Neanderthal. To focus this topic, you could analyze the tools and communication within this species and how that affected their development as a species. Another would be to explore the specific physical traits of hominids and the possible reasons for their development.
An interesting focus for an anthropological paper could be a comparative analysis between two seemingly like subjects. For example, you could analyze two cultures from nearby regions, two schools of anthropological theory, two popular religions and its followers or even two species of hominids. To include the archaeological field into your research paper, compare two tools that an indigenous culture used. During your comparative analysis, note how the two subjects of discussion are similar and dissimilar. Provide evidence of these divisions and provide reasoning for their origins and development.
Because anthropology is the study of people and cultures, your paper could focus on the different social constructs within a particular culture. Not only can you analyze the definition of these constructs, how they are used, ceremonies performed within these cultures and so on, you can explore the origins of these institutions and how they are viewed inside and outside of the culture. For example, the social construction of marriage is popular in many different societies around the globe. You could discuss the concept of marriage in one particular culture, or analyze how marriage is constructed in societies around the world.
There are many possible research topics within the field of linguistics. One approach would be to analyze the work of one or more specific linguists and their body of work. Explore their theories in an effort to support, compare or disprove their discussions. Yet another approach would be to focus on a specific community. For example, you could explore the language of a particular culture and its origin. You could break down the roots of words used and how the spoken language is used to communicate within the society.