Charles Darwin’s 1859 book, On the Origin of Species, is often cited but hardly ever read. My book presents the observations and the concepts that he actually proposed because they continue to guide research in the twenty-first century; and suggest how we should deal with issues of general concern.Darwin’s explanation of Natural Selection, the key mechanism of his theory, cannot be improved on. Darwin wrote:“[A]ny variation, however slight, and from whatever cause proceeding, if it be in any degree profitable to an individual of any species, in its infinitely complex relations to other organic beings and to its physical conditions of life, will tend to the preservation of that individual, and will generally by inherited by its offspring. The offspring, also, will thus have a better chance of surviving […]. I have called this principle, by which each small variation, if useful, is preserved, by the term Natural Selection. (On the Origin of Species, p. 61)Darwin thought that Natural Selection acted slowly. The facts that demonstrate that it can act rapidly were not then known. However, he knew that abrupt transitions had occurred. His solution was “recycling”: an organ that had evolved for one purpose could be modified to serve a new end. Swim-bladders that allowed fish to hover had turned into lungs. Current studies show that brain mechanisms that evolved for motor control now enhance human cognition and language. Neural structures involved in the early stages of vision play a part in recalling memories.Darwin borrowed from his grandfather Erasmus the premise that the development of an organism could provide insights on its evolution—the basis for current “Evo-Devo” studies. Although the role of genes was then buried in an obscure journal and DNA was discovered a century later, Darwin proposed that the environment could directly produce heritable effects. “Epigenetic” DNA that does not specify genes, govern the processes that yield brains and bodies. These processes explain why we don’t look like or generally act like chimpanzees though we share almost 99% of our genes. Some epigenetic processes are directly affected by environmental factors; your grandmother’s diet can lower your lifespan by 30 years.The opening scenes of documentaries showing lions tearing apart their prey have little to do with Darwin’s “struggle for existence.” He devoted chapters to describe how different species profitably interact to enhance survival. Darwin stressed the interplay between ecosystems and biological evolution as well as the unintended consequences of human intervention. And he was one of the first practitioners of the modern “scientific method”—running experiments to confirm, modify, or reject a theory. His pigeon breeding experiment showed that “fancy” pigeons, thought to be distinct species, had descended from the common rock pigeons you see on city streets.Darwin’s theory will become clear in examples drawn from his work, On the Origin of Species, what’s on the shelves of your supermarket, and current research including my own. And there will no need to google to decipher jargon.