part of a divine plan (theistic evolution). This left unanswered the question of why each step should occur, and Cope switched his theory to accommodate functional adaptation for each change. Still rejecting natural selection as the cause of adaptation, Cope turned to Lamarckism to provide the force guiding evolution. Finally, Cope supposed that Lamarckian use and disuse operated by causing a vitalist growth-force substance, "bathmism", to be concentrated in the areas of the body being most intensively used; in turn, it made these areas develop at the expense of the rest. Cope's complex set of beliefs thus assembled five evolutionary philosophies: recapitulationism, orthogenesis, theistic evolution, Lamarckism, and vitalism. Other palaeontologists and field naturalists continued to hold beliefs combining orthogenesis and Lamarckism until the modern synthesis in the 1930s. Status In science The stronger versions of the orthogenetic hypothesis began to lose popularity when it became clear that they were inconsistent with the patterns found by paleontologists in the fossil record, which were non-rectilinear (richly branching) with many complications. The hypothesis was abandoned by the mainstream of evolutionists when no mechanism could be found that would account for the process, and the theory of evolution by natural selection came to prevail. The historian of biology Edward J. Larson commented that The modern synthesis of the 1930s and 1940s, in which the genetic mechanisms of evolution were incorporated, appeared to refute the hypothesis for good. As more was understood about these mechanisms it came to be held that there was no naturalistic way in which the newly discovered mechanism of heredity could be far-sighted or have a memory of past trends. Orthogenesis was seen to lie outside the methodological naturalism of the sciences. By 1948, the evolutionary biologist Ernst Mayr, as editor of the journal Evolution, made the use of the term orthogenesis taboo: "It might be well to abstain from use of the word 'orthogenesis' .. since so many of the geneticists seem to be of the opinion that the use of the term implies some supernatural force." With the rise of evolutionary developmental biology in the late 20th-early 21st centuries, however, which is open to an expanded concept of heredity that incorporates the physics of self-organization, ideas of constraint and preferred directions of morphological change have made a reappearance in evolutionary theory. For these and other reasons, belief in evolutionary progress has remained "a persistent heresy", among evolutionary biologists including