Paleontology is the study of fossil animals and plants. Human paleontology focuses exclusively on fossils related to the human lineage. Human paleontology is highly interdisciplinary; to recover, describe, and interpret human fossil remains, its researchers need knowledge of cultural anthropology, archaeology, biology, paleontology, and geology.
Paleontology and Human Paleontology
Fossils, the remains or imprints of dead organisms, are the only physical evidence humans possess of ancient life. While fossils are generally formed from bone, shell, or wood, under very specific conditions, fossils may be formed from soft tissue, animal tracks, skin impressions, and feces. Sometimes, bones are disturbed by scavengers or water movement prior to fossilization; the study of what happens to a bone from the time of the organism’s death to its discovery is called taphonomy.
Research in paleontology focuses on reconstructing the history of life on Earth. Fossils provide important clues about past environments, ecosystems, and evolution. Paleontology incorporates knowledge from many fields to understand the processes of evolution and to reconstruct ancient life. Most fossils studied by paleontologists are anywhere from thousands to several millions of years old. Human paleontology focuses on fossils of the human lineage, thought to begin between 5 and 8 million years ago.
Like paleontology, human paleontology utilizes evolutionary theory and the scientific method to test hypotheses about past lifeways and relationships. Ecological niche theory and estimates of inter- and intraspecific competition levels also help reconstruct behaviors and evolutionary pressures. Morphometric and cladistic methodologies help researchers define fossil species and reconstruct relationships between fossil species and between fossil and living species.
However, human paleontology differs from paleontology in that it studies human origins. This self-reflexive process, humans studying humans, is subject to bias not seen in studying, say, the evolution of birds. Most animals transmit information from generation to generation primarily through genetics (the purview of biological evolution). However, humans have a well-developed ability to pass information along through culture: teaching and learning. While culture is by no means exclusive to humans, humans utilize it so very heavily that it has arguably interfered with evolutionary pressures normally experienced by other animals.
Because of the heavy influence of culture on human adaptation, the application of some paleontological methods can be problematic. While early fossil humans, like other animals, had to adapt biologically and behaviorally to specific environments or ecological niches via natural selection, this is less true for later fossil humans. When fossil humans began to rely on cultural adaptations, such as fire and toolmaking, to assist them in survival, these adaptations created a cultural buffer between them and their environment. If humans can warm themselves through the controlled use of fire, winters are no longer as dangerous as they once were. Communication/language skills and technological sophistication have played large roles in shaping human adaptation to the environment. It is difficult to know how to interpret to what extent the forces of natural selection affected the survival of a species that relies so heavily on technology.
The terms human paleontology and paleoanthropology are often used interchangeably, although the former is primarily focused on the study of human fossils and the latter is a broader multidisciplinary activity. Paleontology does not usually deal with artifacts made by humans, but due to the uniqueness of the human biocultural adaptation, human paleontologists do look at artifacts as well as modern human and primate behavior to better understand the fossil record and humans’ place in nature.
Areas of Research Within Human Paleontology
The human fossil record, like all fossil records, is incomplete. Fossil skeletons are rarely complete. Only a very small percentage of the original members of any species experienced the accident of preservation as fossils. The challenge for human paleontologists is to reconstruct anatomy, behavior, and ecology from these specimens.
Osteology is the study of the structure and function of bones. The structure of bones is genetically based, but bones also respond to developmental events, stresses, and injuries to the body. Human paleontologists have to become very familiar with variation (between sexes, within any population, and between populations) exhibited by the modern human species. Some of this variation is genetic, but variation is also caused by unique life events experienced by the individual. The definition of fossil species rests on understanding of how much variation existed in the past, a difficult question, indeed. Familiarity with the principles of biomechanics (the study of the forces exerted by muscles and gravity on the skeleton) and the skeletons of primates and other animals help human paleontologists reconstruct the movement and behavior of fossil humans.
Dental anthropology, or the study of the dental evolution, variation, and morphology of modern and ancient human populations, is also a vital area of inquiry. Since teeth are composed of enamel, the hardest substance in the body, they are more likely to survive in the fossil record. Teeth are an important source of data in the reconstruction of fossil human diet, behavior, and species variation. Through the study of anatomy, human paleontologists can describe a species’ size, diet, locomotor style, ecology, and even shed light on behavioral issues such as group size and social organization.
Human paleontologists use genetics to help answer questions about recent common ancestry and past population movements. They can measure how closely two species are related by comparing their DNA. Species that are similar genetically share an ancestor in the not-too-distant past. When geneticists compare human and chimpanzee DNA sequences, less than 2% of the sequences are different, meaning that these two species have a very recent common ancestor. Human paleontologists can estimate how long ago two species shared a common ancestor by using a “molecular clock,” which calibrates an estimated mutation rate against time of divergence of different lineages. Scientists also use the concept of a molecular clock, but use mitochondrial DNA (or mtDNA) to track past population movements and to determine when and where the earliest modern human ancestor lived.
Finally, human paleontologists must look to behavioral models seen in modern humans and living primates to interpret fossil human behavior. Primate and human ecological models inform research on dietary adaptations and food-getting strategies, activity patterns, ranging behavior, and male/female reproductive strategies and social hierarchies.
A holistic anatomical study, including paleobotanic, paleontological, and paleoenvironmental associations, combined with molecular genetics and studies of behavioral models help human paleontologists understand the broader picture of human evolution.
References:
- Aiello, L., & Dean, C. (1990). An introduction to human evolutionary anatomy. San Diego: Academic Press.
- Boyd, R., & Silk, J. B. (2003). How humans evolved (3rd ed.). New York: Norton.
- Johanson, D., & Edgar, B. (1996). From Lucy to language. New York: Simon & Schuster.
