The Evolution Of Human Behavior Essay Research

The Evolution Of Human Behavior Essay, Research Paper Charles Darwin’s theory of natural selection was widely rejected when it was first introduced in 1859 in On the Origin of Species. The Church was reluctant to accept it since it contradicted its teachings. Even the scientific community hesitated to embrace such a revolutionary, yet logical, new idea. Since then, much evidence has been uncovered that lends support to natural selection. The evidence has come primarily in the form of fossils, which lends support to the tenets of natural selection. These tenets put forth by Darwin are as follows: -Characters vary within populations. -Populations increase at an exponential rate. -Exponential increase is prevented by struggle for existence; not all individuals can survive and

reproduce. -During the struggle for existence, those individuals with the most favorable traits for their respective environment are more likely to survive and reproduce. This differential survival and reproduction constitutes natural selection. -These favorable characters are passed on to the next generation, and increase in frequency over time. -(Thompson 10) The fossil record shows a gradual change in morphology compatible with the theory of natural selection. In other words, the evidence supports the idea that the physical form of organisms gradually change over time in response to selection pressures from its environment. However, very little evidence has been found showing that the behaviors of organisms also evolve in the same Darwinian manner. Because behaviors do not

fossilize, most of the evidence supporting the evolution of animal behavior has come about through deductive reasoning based on fossils as well as current primate behaviors. For example, brain size, which can be deduced from skull size, is used to determine certain behaviors. Large brains correlate to large body sizes. This means that larger brained animals will have larger foraging areas, which entails a tendency to exploit new environments. Large brains also must do more to sustain themselves, meaning that they have functions which are more numerous and complex. Given these correlations between brain size and behavior, it might surprise one to learn that larger brain size has actually been linked to decreased species survival. Australopithecus afarensis, an early primate

closely related to man, had a slightly larger brain than chimpanzees (approximately 500 cc) and lived about a million years. Homo erectus, which had a brain of about 1000 cc lived 750,000 years; Neanderthal had a brain of about 1450 cc and lived 300,000 years. Homo sapiens have brain size of approximately 1350 (which is larger than the Neanderthal when put into proportion with body size), and have only existed for a relatively short period of time with an uncertain future (Thiessen 250). In addition to studying brain size, efforts to explain the behavior of humans by studying the behavior of man’s closest living relative also exist. These include the great apes, in particular, the chimpanzee. People studying the great apes work under the premise that “in related species, the

more widespread a trait is, the phyligenetically older it is likely to be” (Peters 192). Therefore, comparing behaviors of humans and chimpanzees give scientists a way of tracing the origin of a particular behavior. Once the origin has been found, they can then go forward in time to plot the evolution of the particular trait. Scientists also heavily rely on deductive reasoning to help explain why certain behaviors came about. This involves speculation as to why behaviors benefit certain organisms. These efforts to link behavior to evolutionary biology has spawned a new field of study called sociobiology. Prior to Darwinism and sociobiology, people explained human behavior according to two opposing views. The first view, supported by Marx and Rousseau, was referred to as the