There has with respect to understanding human evolution, thus far, hardly been any greater an academic marriage than that which has occurred between physical anthropology and genetics. For anthropologists the union has been particularly beneficial as DNA has been incorporated into the quest to understand human evolution. Some scholars have referred to this as the culmination of the evolution of the once distinct fields represented symbolically by Darwin’s theories on evolution and Mendel’s speculation regarding genes; one scholar has opined that Darwin and Mendel are the core, the essentials of understanding.
These basics work together. The gene pool — the hereditary property of a population of animals — maintains the variation of the population or species, and mutation tends to increase that variation. Darwin’s selection cuts back the less favorable variation, in that way sculpting the inheritance of the species. (Howells 8) Fossils and genes, taken together, illuminate in ways that one without the other simply cannot. This refers to the discovery of positive knowledge as well as the discovery of long-established fallacies in the field of physical anthropology (Marks 131). This essay will focus on a few types of positive knowledge regarding the evolution of human DNA.
More specifically, this essay will discuss how DNA variation can be used to explain some of the evolutionary physical features for sexual differences in humans as they pertain to language, sexuality, and visual spatial skills. As a preliminary matter, it is important to acknowledge that human sex differences were not always as pronounced as they are today. There were genetic variations that occurred over a long period of time and these genetic differences are evident in the fossils used by physical anthropologists to piece together how and why DNA has evolved as it has over the course of time.
Scholars seem to agree that the evolution of human DNA is unique in certain respects; for purposes of this essay, it is significant to note that, regarding sexual differences in species, “It is apparent that these same cross-species sex differences have become more pronounced in humans” (Joseph 35). The evolution of human DNA with respect to sexual differences is greater than has been found in studies of other species. It has been demonstrated that DNA evolution led to Homo erectus females experiencing a vaginal reorientation at the same time that males experienced a change in pelvic structure (Joseph 35).
The consequences were tremendous as this likely resulted in the development of long-term relationships between males and females; this is because, rather than being dependent on estrus in order to get pregnant, females were now physically and genetically configured to be sexually receptive continuously rather than sporadically. These long-term relationships also seem to have coincided with males and females establishing more permanent or semi-permanent homes. It can be argued, to some degree at least, that this genetic variation led to an embryonic notion of marriage and home.
These human sex differences were further accelerated with the genetic evolution of the brain; indeed, as the brain became larger, “this required a larger birth canal and an increase in the sexual physical differentiation in the size and width of the H. erectus” (Joseph 35). DNA varied to accommodate these changes and they are manifest even today in the way that women walk as well as in the more fragile nature of their pelvic bones when compared to their male counterparts.
As the female was evolving there were practical consequences; for instance, “The transformation of the human female hips and pelvis, however, also limited her ability to run and maneuver in space, at least, compared to most males” (Joseph 35). These DNA variations thus functioned to separate males and females and to lay the physical groundwork for other changes. This evolution in human DNA, in turn, led to a division of labor predicated on these newly exaggerated differences between the sexes. Generally speaking, women became gatherers and men became hunters.
Each of these roles demanded different types of skills and the human animal adapted through the mechanism of its DNA. The female role demanded careful language skills rather than violence whereas the male role demanded aggression and physical strength. In explaining how the male DNA evolved to adapt to the male’s developing function, one scholar has noted that “successful hunting requires prolonged silence, excellent visual-spatial and gross motor skills, and the capacity to endure long treks in the pursuit of prey. These are abilities at which males excel, including modern H. apiens” (Joseph 35). In short, many of the human sexual differences noted today can be traced to the ways in which human DNA has evolved over time in order to adapt to changed environments and to changed sex roles. In the final analysis, even a cursory examination of the history of the evolution of human DNA suggests rather persuasively that there are watershed events which can aid in understanding the uniqueness of sexual differentiation in humans and how sex roles evolved in response to that sexual differentiation.