Naturally, human beings are ever considered as the source of norm of conduct or the creatures that define their ways of life and resenting constrains and obstacles of leading or living a virtuous life. Human nature has been evolving since time in memorial. Each historic era is usually defined by distinct characteristic of human nature as well as the psychological concepts. However, since the human generation moves from one era to another, they tend to shade off some defining human characteristic of a given era while moving to other era. Nonetheless, some of the characteristics are carried into the new era. Therefore, the nineteenth century and twentieth century are defined by some similarity and differences in the conceptions of human nature and psychology. Similarities and Differences The end of the nineteenth century was marked with numerous developments that led to rejection of Victorian principles. The Victorian age was marked by shift an agricultural society to an industrial society. The period was as well defined by the decline in traditional religious beliefs and adoption of moral aesthetic. However, they retained the literature values maintaining that the literature would enable them understand and perfectly adapt to the newly founded society (Jeeves, 2006). It means both the nineteenth and twentieth centuries had same literature but remarkable, different economic activities and religious beliefs (Gopal, 2008). Some novelists defined the subsequent change in a society that marked the end of the 19th century and the beginning of the 20th century as a breaking down social structure. They intensively talked about social mares and expressed their topic on realism. According to Darwin, human is an animal creature that is conditioned by influences that are beyond his or her control; thus, human being is devoid of free, moral choice or will. In other words, human is a creature that usually shaped by external factors such as environment, hereditary, and immediate circumstances pressure. Considering Darwin’s view, though there was a change in both industrial and social life of human nature they both shared some characteristics (Stevenson, 2007). Putting Lewontin work in perspective, as a population geneticist of the nineteenth century, he argued that human species are highly varied in their genes than within racial population. He further noted that racial identity features that include hair, color of the eye, and skin color are more aligned to adaptation that is clearly defined by geographical conditions among other factors (Gopal, 2008). This nineteenth century psychological reasoning overlaid the basic genetics of commonality among the human species. In relation to genetics and human commonality, the psychologists of the twentieth century did not argue much but rather used more sophisticated machine to examine and understand human genes. The contributions of Lewontin limited the applicability of Jensen’s IQ testing between different races. Jansen used conversational racial groups to compare the IQ scores to come to the proof of genetic difference between racial groups (Jeeves, 2006). However, Lewontin dismissed the claims that the consistent difference in genetics lies in the differences in the brain within races. He added that if Jensen could not provide any further evidence, then IQ also was also influenced different physical environment or social.