The theory of natural selection was postulated by Charles Darwin. He proposed that organisms with advantageous traits are more likely to survive and reproduce, passing on those traits to their offspring. Over time, this process leads to the evolution of new species. This concept is known as natural selection because the environment "selects" which individuals are better adapted to survive and reproduce. Darwin developed this theory after observing the diversity of life during his travels on the HMS Beagle, and conducting experiments on plant and animal breeding. His book "On the Origin of Species" was published in 1859 and became one of the most influential scientific works in history, revolutionizing our understanding of life and the natural world.