Darwin's Theory Of Natural Selection

According to Levin (2003:102) the discovery of natural selection, by Darwin and Alfred Russel Wallace, must itself be counted as an extraordinary philosophical advance. The concept of natural selection had remarkable power for explaining directional and adaptive changes. Its nature is simplicity itself. It is not a force like the forces described in the laws of physics; its mechanism is simply the elimination of inferior individuals. “Furthermore, the objective of selection even may change from one generation to the next, as environmental circumstances vary. By adopting natural selection, Darwin settled the several-thousand year- old argument among philosophers over chance or necessity. Change on the earth is the result of both, the first

Yet the concept of species adaptation was not so radical at the time. Scientists had been debating whether animals evolved decades before Darwin put forth his theory.’’ While Darwin’s ideas initially challenged long-held scientific and religious belief systems, opposition to much of Darwin’s thinking among the scientific communities of the English-speaking world largely collapsed in the decades following the publication of On the Origin of Species. Yet evolution continued to be vigorously rejected by British and American churches because, religious leaders argued, the theory directly contradicted many of the core teachings of the Christian faith.’’ ( Ospovat, 1995:200). Marks suggest that genetic variation is the result of mutation, gene flow between populations and sexual reproduction. In asexually reproducing organisms, some genetic variation may still result from random mutation. Mutations, or changes to the coding patterns of DNA, lend to genetic variation when they are heritable, meaning they pass between generations from parents to offspring. Mutations can be either harmful or beneficial, and both types of mutations are heritable. Transfer of genetic material between populations is also an important contributor to genetic variation; populations in isolation are at risk

Whether or not the australopithecines were fully adapted bipeds is still hotly debated in the literature. There are several important adaptations to bipedal locomotion that can be observed on skeletal material. First, the foramen magnum is shifted forward, underneath the skull. This positioning is indicative of the angle at which the spinal chord enters the skull. The degree of sexual dimorphism present in the australopithecines has been hotly debated. For some skeletal samples, there is debate about whether a high degree of sexual dimorphism exists or whether there are two species of hominid present in the sample, one large and one small. While it is by no means conclusive due to the uncertainty inherent in estimating body size from fossil specimens, it now appears that the australopithecines exhibited a degree of sexual dimorphism considerably greater than that observed in modern humans and chimpanzees, but less than that observed in gorillas Interestingly though, most australopithecines are relatively rare among anthropoids in being highly dimorphic in terms of body size, but not in canine size. “The degree of sexual dimorphism is significant because this has implications for social organization and mating