Natural selection is usually defined as the process by which forms of life having traits that better enable them to adapt to specific environmental pressures, as predators, changes in climate, or competition for food of mates, will tend to survive and reproduce in greater number than others of their kind, thus ensuring the perpetuation of those favorable traits in succeeding generations. Charles Darwin and Alfred Wallace developed the theory of evolution by natural selection and jointly presented papers on the subject in 1858. It is based on the finding that some distinctions between people in a group can be passed down across generations. Darwinism, or Darwin's theory, is a theory of evolution created by Charles Darwin stating that all life forms arise, change and develop from a process of natural selection. Natural selection is the process of changes in evolution due to the survival of certain individuals in a species. It is one of the most important parts of the theory of evolution. Darwin's idea provided a straightforward yet persuasive Step-by-step explanation for the diversity of species on Earth. Because various locations have distinct circumstances and survival possibilities, natural selection selects the organisms that are best adapted to that particular environment.