Human Evolution

Introduction

Human evolution (or humanization) explains the process of biological evolution of the human species from their ancestors to the current state. The study of this process requires an interdisciplinary analysis which unites knowledge from sciences such as genetics, the physical anthropology, the paleontology, the stratigraphy, the geochronology, the archeology and linguistics (Lewin, 33-42).

The term human, in the context of its evolution, refers to individuals of the genus Homo. However, studies of human evolution include other hominins, such as Ardipithecus, Australopithecus, and so on. Scientists have estimated that the evolutionary lines of humans and chimps split it between 5 and 7 million years. From this separation the human race continued branching giving rise to new species, all now extinct except for Homo sapiens (Lewin, 91-103).

Discussion

For a long time, scientists believed that human evolution has been more or less linear: one form after another, and each was a new progressive, closer to modern man than the previous one. It is now clear that it was much harder. The evolutionary tree of hominids has been very branched. Time intervals of the existence of many species overlap strongly. Sometimes several different species of hominids, at different “levels” close to the man coexisted in the same biotope (eg, Homo ergaster, and Paranthropus boisei). Situation where a family of hominids represented by a single species (as now) - in principle is not typical. For example, even in the relatively recent past - only 50,000 years ago - on Earth as much as there were at least four species of hominids: Homo sapiens, H.neandertalensis, H.erectus and H.floresiensis (Degler, 24-29).

Evolution: Theory and Evidence

The theory of Darwinian evolution is considered, with justice, as the major unifying principle of biology. Darwin was not the first to propose a theory of evolution, but it was the first to describe a valid mechanism by which it could happen. His theory differed from theories in which he imagined prior to evolution as a dual process, which depended on: 1) the existence of heritable variation among organisms, and 2) the process of natural selection by which some organisms, under heritable variations, left more offspring than others (Stringer, 116-123).

There are many evidences that show the existence of the evolutionary process. Distinguishing the field they came from, scientists can recognize five sources of evidence: the observation directly, biogeography, the fossil record, the study of the homologies and the imperfection of adaptation (McHenry, 77-85).

Since Darwin's time, has accumulated a wealth of new evidence in all these categories, particularly at the cellular, subcellular and molecular level, highlighting the historical unity of all living organisms. A central weakness of Darwin's theory, which remained unresolved for many years was the absence of a valid mechanism to explain the inheritance (Noonan, 547-553).

In the 1930s, the work of many scientists resulted in the synthetic theory of evolution, which combines the principles of genetics Mendelian to Darwinian Theory. The Synthetic Theory has provided-and continues to provide-the basis for the work of biologists in their attempts to unravel the details of the history of ...