Organic evolution refers to the gradual and continuous process through which living organisms have changed over time, resulting in the diversity of life seen today. Biological anthropology relies heavily on the principles of organic evolution to explain the origin, variation, adaptation, and development of humans and other primates. Several theories have been proposed by scientists to explain the mechanism of evolution. Among the most important are Lamarck's Theory of Inheritance of Acquired Characters, Darwin's Theory of Natural Selection, De Vries' Mutation Theory, and the Modern Synthetic Theory of Evolution. Jean Baptiste Lamarck was one of the earliest scientists to present a systematic theory of evolution. According to Lamarck, environmental changes create new needs in organisms. To satisfy these needs, organisms develop new habits. The organs that are frequently used become stronger and more developed, while those that are not used gradually degenerate. Lamarck further proposed that these acquired characteristics are inherited by the offspring. His classic example was the giraffe, which supposedly developed a long neck through repeated stretching to reach higher leaves, and this acquired trait was passed on to future generations. Charles Darwin proposed the Theory of Natural Selection after extensive observations made during his voyage on HMS Beagle. Darwin observed that organisms produce more offspring than can survive, leading to competition for limited resources. Individuals within a population show variations, and those possessing favourable variations are more likely to survive and reproduce. These advantageous traits are inherited by future generations, while less adapted individuals are gradually eliminated. Over long periods, natural selection results in the formation of new species. Darwin's theory was supported by observations from nature, artificial selection, comparative anatomy, fossils, and biogeography. Hugo De Vries introduced the Mutation