Ant 333: lecture #1 patterns in primate evolution. Adaptation is at core of modern evolutionary biology. Natural selection is 1st and foremost an explanation of adaptation. Hard to detect, test, and define adaptation. Dangerous concept, a lot of stories made up. Process whereby any heritable features, anatomical or behavioral, that enhance the fitness of an organism relative to its peers, increase in frequency in the population in succeeding generations. Units of selection in natural selection only pertain to one individual. Doesn"t have to result in biological evolution, and not all biological evolution is due to natural selction. An adaptation is a characteristic that allows an organism to live and reproduce in an environment where it probably could not otherwise exist (vermeij, 1978). Also refers to process whereby organisms obtain their adaptive characteristics. Evolutionary biologists refer to an adaptation as a trait that evolved as the result of natural selection.