IntroductionBiological evolution is a descent with modifications. Theories of evolution have their roots in early Greek and Roman culture. Before the 7th century BC, people believed that supernatural forces were responsible for life. The philosophers Plato and Aristotle opposed this doctrine. They used logic to explain the origins of life. It was commonly accepted that the earth was only a few thousand years old, that species were immutable, and that life was organized linearly. In the 7th century, naturalist John Ray used the term “species” as a basic unit of classification. In the 18th century, Carolus Linnaeus created a hierarchical classification system to organize species based on similarity using phylogenetic trees. In 1809, the French theorist Jean-Baptiste Lamarck published his theory on the inheritance of acquired traits. In 1830, Charles Lyell introduced uniformitarianism as a mechanism of evolution; the theory that geological change is relatively constant. In the mid-nineteenth century, Alfred Wallace and Charles Darwin both individually conceived of natural selection as a mechanism of evolution. Darwin received credit for the theory of natural selection because he published his book, On the Origin of Species, before Wallace. In 1865, Gregor Mendel is the founder of modern genetics thanks to his work on crosses of pea plants. To this day, the work of Mendel and Darwin is widely accepted. Important actors in the history of evolutionary thought Aristotle In 300 BC, in Greece, Aristotle made his contribution to evolutionary thought. Aristotle organized living organisms hierarchically. This concept was known as scala naturae, or the Great Chain of Being. With the plants at the bottom, Aristotle's nat scale......in the center of the paper......They discovered that when the climate was dry, no major changes occurred in the brain, but when the climate changed, changes occurred in brain size. As the size of the brain increased, stone tools appeared. Homo erectus was the first to leave Africa, hunt, make fire and create societies. Homo erectus lived 1.3 million years ago in the Great Rift Valley. Homo erectus evolved to have thinner arms, longer legs and larger brains. This is considered a huge evolutionary step from ape bodies to more human ones. The skeleton of Turkana Boy was found in northern Kenya. At 5 feet 3 inches, Turkana Boy had a build closer to that of a human than that of an ape. Turkana Boy represents the first true human being. Although he was one of the first humans, he was still very primitive. Turkana Boy had a lower forehead and less brain capacity than a human.