 The term “heritable” applies to traits that vary in the population and are more similar in parents and offspring than they are in randomly selected individuals in the population. We inherit numerous attributes from our parents including their religious beliefs and, if we are lucky, their vast fortunes. The kinds of hereditary traits that biologists are interested in are those that are reliably transmitted from one generation to the next as a matter of biology. Darwin (1859 [1968]), working without the advantages that genetics would later bring, discussed hereditary traits at the level of phenotypes. Darwin demonstrated that natural selection sorts among hereditary variations, for example, the height of an organism, its weight, the color of its coat and so on. Most contemporary discussions of heredity constrain hereditary traits to those that can be demonstrated to be passed on genetically. The concept of “heritability” was introduced “to quantify the level of predictability of passage of a biologically interesting phenotype from parent to offspring” (Feldman, 151). Heritability is usually assessed by complex statistical analysis, careful experimentation or both.