According to the leading scientific theories, the history of Earth covers approximately 4.6 billion years (4,567,000,000 years), from Earth’s formation out of the solar nebula to the present. The history of the world is the memory of the past experience of Homo sapiens around the world, as that experience has been preserved, largely in written records. The origin of man is still very obscure.[20][21][22] After the dawn of man, ancient human history begins with the invention, independently at several sites on Earth, of writing,[23] which created the infrastructure for lasting, accurately transmitted memories and thus for the diffusion and growth of knowledge
