Biological anthropologists have discovered a previously unknown fossil species. The species lived about 4.4 million years ago in Africa. The dating of this fossil species places it closer in time to the last common ancestor of humans and chimpanzees than most other known fossil species. This newly discovered species has an interesting mix of traits. For example, it has adaptations for climbing in trees as well as for walking on two legs on the ground. It does not directly resemble any of the living ape species, which suggests that the living ape species (including humans) have each become adapted for their own environmental contexts over time. What is the primary subfield of biological anthropology addressed in this research