Biological anthropology is the study of human biological variation and its genetic and environmental causes within the framework of evolution. The roots of physical anthropology, the name usually given to this subfield of anthropology until recently, lie in the 19th century. However, there was no university-based training in the subfield until well into the 20th century. Using observation and measurement, physical anthropologists in the early days studied human evolution, classified human races, and collected data on human variation, taking anthropometric measurements and observing skeletal traits. In understanding human evolution, physical anthropologists used the fossil record to draw many of their conclusions. As a result, the field of physical anthropology was greatly influenced by anatomy and paleontology. The term biological anthropology slowly came into use, in part through the influence of the modern synthetic theory of evolution, also known as neo-Darwinism, or simply the evolutionary synthesis. Subsequently, physical anthropology was transformed from a science based in typological thinking, the idea that there was an essence or type based on morphological characters that marked each human race, to one grounded in evolutionary biology and population concepts.
With the emergence of the evolutionary synthesis during the middle part of the 20th century, physical anthropologists slowly began working with data other than anthropometric measurements in the form of Mendelian traits, like the blood group antigens to incorporate genetics into their analyses. The modern evolutionary synthesis can be understood as a unification of the macroevolutionary theories of natural selection and the microevolutionary theories of changes in the genetics of populations over time. However, to fully understand the synthesis and its impact on biological anthropology, the underlying history behind evolution and its effects on the human species must be examined briefly.
In 1858, Alfred Russel Wallace published a paper supporting descent with modification. The following year, Charles Darwin published On the Origin of Species, in which he formally presented his theory of natural selection supporting the concept of evolution. Darwin defined natural selection as the adaptation of an organism to its environment through selective reproduction. Many years later, after the development of genetics, it came to be understood that organisms were selected for the genes that benefit survival and procreation in response to environmental pressures. Both Wallace and Darwin are considered fundamental contributors to the development of the theory of evolution.
Somewhat later, Francis Galton, cousin of Darwin, suggested that evolution occurred discontinuously. During the same time, Gregor Mendel presented his data on the inheritance of traits in peas, which went largely unnoticed until their rediscovery in 1900. Three scientists in that year independently studied and clarified Mendel’s ideas, which explained the transmission of traits and discrete units that eventually came to be known as genes.
Scientists who took Mendel’s approaches and conceptualized them in populations recognized the processes of mutation, random genetic drift, and migration as mechanisms capable of altering gene frequencies. Under circumstances devoid of disturbances like these, gene frequencies would remain relatively constant from one generation to the next. However, if mutation, random genetic drift, or migration were operating in a population, gene frequencies could change regardless of whether the change conferred a survival advantage to the organism. Many of the scientists studying Mendel’s principles gradually began to support the idea that mutations were the most important evolutionary mechanism for change in populations, not natural selection, as Darwin had suggested.
Biometry, statistical analysis applied to biology, developed during the decades just before the rediscovery of Mendel’s work and ideas. Biometricians believed that natural selection occurred continuously, incorporating small changes over long periods of time. As a result of these scientific advances in the first decade of the 1900s, there developed a clear division between supporters of Mendel’s laws and the biometricians. The division between these two groups served as a platform for debate over the mechanism of evolution leading into the following decades.
Determining a mechanism for evolution, whether it occurred continually, over a long period of time, or in leaps and bounds, was pushed to the forefront in the biological sciences. Many geneticists of the time tried to resolve the different theories of how evolution occurred. Likewise, geneticists and others tried to understand how traits like those of interest to the biometrists, what we now label metric traits, could be understood in Mendelian terms. The answer came in 1918, when Ronald Fisher published a paper explaining the correlations between relatives and Mendelian inheritance. This important paper represented the first comprehensive attempt to reconcile the differences between the Mendelians and biometricians relative to metric traits like height, intellectual functioning, and the like.
However, developments in genetics and developments in selection theory, brought about by mathematical and experimental modeling studies on evolution, remained divided concerning the theories of how evolution occurred. Fisher’s subsequent work, as well as that of J. B. S. Haldane and Sewall Wright, led to the development of classical population genetics and the theoretical underpinnings of the evolutionary mechanisms that change populations over time.
The first successful attempt to unify the evolutionary theories and demonstrate how they applied in natural populations occurred in 1937, when Theodosius Dobzhansky, a Russian biologist, published Genetics and the Origin of Species. His book synthesized the theoretical mathematical models of evolution developed by population geneticists such as Fisher, Haldane, and Wright, with natural population studies by field biologists like Dobzhansky himself.
Following Dobzhansky’s book, biologists such as Julian Huxley, Ernst Mayr, and George Gaylord Simpson published books of their own throughout the 1940s, each of which supported Dobzhansky’s synthesis. The support from Huxley, Mayr, Simpson, and their colleague led to the unification of researchers from a wide variety of biological sciences. Scientists from the fields of genetics, embryology, anthropology, ecology, physiology, microbiology, and medicine were all involved in the synthesis and its aftermath. Working together, they found a way to integrate genetics into the framework of natural selection that satisfied all requirements for a unified theory, and thus neo-Darwinism was born.
There is general consensus among historians of biological anthropology that the influence of the evolutionary synthesis on research in the subfield began in earnest after the Second World War. Biological anthropologists slowly realized the value of including population concepts, based on the theories and applications of evolutionary genetics, in their research. It provided a new tool that would enable them to conceptualize changes in human biological characteristics through time. Anthropologist Sherwood Washburn was among the pioneers during the 1950s and 1960s in the application of neo-Darwinism to the evolution of primates, specifically as it relates to the origin of humans. Many point to the publication of Washburn’s paper on “The New Physical Anthropology” in 1951 as the watershed moment for the influence of population thinking in the field.
This shift in thinking came about because many biological anthropologists were in essence retooling. Grounded in anatomy, paleontology, and taxonomy, they were now being exposed to the works of Dobzhansky, Mayr, and others, as well as developments in genetics, and the immediate impact was on the training being offered to the next generation of students in the subfield. Teaching was more apt to include exposures to population genetics, demography, ecology, and other population-based fields with an evolutionary perspective. Historians of biological anthropology have stressed the impact of the modern synthetic theory across diverse areas of research in the subfield, including primate field studies, human paleontology, hominid paleoecology, skeletal biology, human adaptation, and, of course, studies of biological variation in living human populations. The movement toward population thinking clearly had its greatest outcome in the broadening of biological anthropology from a science based in anatomy and paleontology to one that attempts to understand biological variation in the human species and the primates, and its causes, past and present.
- Mayr, E., & Provine, W. B. (Eds.). (1980). The evolutionary synthesis: Perspectives on the unification of biology. Cambridge, MA: Harvard University Press.
- Smocovitis, V. B. (1996). Unifying biology, the evolutionary synthesis, and evolutionary biology. Princeton, NJ: Princeton University Press.
- Spencer, F. (Ed.). (1982). A history of American physical anthropology 1930-1980. New York: Academic Press.