Orthogenesis is an obsolete biological hypothesis that organisms have an innate tendency to evolve in a definite direction towards some goal (teleology), due to some internal mechanism or "driving force". According to the theory, the largest-scale trends in evolution have an absolute goal such as increasing biological complexity. Prominent historical figures who have championed some form of evolutionary progress include Jean-Baptiste Lamarck, Pierre Teilhard de Chardin, and Henri Bergson.
The term orthogenesis was introduced by Wilhelm Haacke in 1893 and popularized by Theodor Eimer five years later. Proponents of orthogenesis had rejected the theory of natural selection as the organizing mechanism in evolution for a rectilinear (straight-line) model of directed evolution. With the emergence of the modern synthesis, in which genetics was integrated with evolution, orthogenesis and other alternatives to Darwinism were largely abandoned by biologists, but the notion that evolution represents progress is still widely shared; modern supporters include E. O. Wilson and Simon Conway Morris. The evolutionary biologist Ernst Mayr made the term effectively taboo in the journal Nature in 1948, by stating that it implied "some supernatural force".Letter from Ernst Mayr to R. H. Flower, Evolution papers, 23 January 1948 The American paleontologist George Gaylord Simpson (1953) attacked orthogenesis, linking it with vitalism by describing it as "the mysterious inner force". Despite this, many museum displays and textbook illustrations continue to give the impression that evolution is directed.
The philosopher of biology Michael Ruse notes that in popular culture, evolution and progress are synonyms, while the unintentionally misleading image of the March of Progress, from apes to modern humans, has been widely imitated.
Definition
The term orthogenesis (from Ancient orthós, "straight", and Ancient , "origin") was first used by the biologist Wilhelm Haacke in 1893. Theodor Eimer was the first to give the word a definition; he defined orthogenesis as "the general law according to which evolutionary development takes place in a noticeable direction, above all in specialized groups".
In 1922, the zoologist Michael F. Guyer wrote:
According to Susan R. Schrepfer in 1983:
In 1988, Francisco J. Ayala defined progress as "systematic change in a feature belonging to all the members of a sequence in such a way that posterior members of the sequence exhibit an improvement of that feature". He argued that there are two elements in this definition, directional change and improvement according to some standard. Whether a directional change constitutes an improvement is not a scientific question; therefore Ayala suggested that science should focus on the question of whether there is directional change, without regard to whether the change is "improvement". This may be compared to Stephen Jay Gould's suggestion of "replacing the idea of progress with an operational notion of directionality".
In 1989, Peter J. Bowler defined orthogenesis as:
In 1996, Michael Ruse defined orthogenesis as "the view that evolution has a kind of momentum of its own that carries organisms along certain tracks".
History
Medieval The possibility of progress is embedded in the mediaeval great chain of being, with a linear sequence of forms from lowest to highest. The concept, indeed, had its roots in Aristotle's biology, from insects that produced only a grub, to fish that laid eggs, and on up to animals with blood and live birth. The medieval chain, as in Ramon Lull's Ladder of Ascent and Descent of the Mind, 1305, added steps or levels above humans, with orders of angels reaching up to God at the top.
Pre-Darwinian The orthogenesis hypothesis had a significant following in the 19th century when evolutionary mechanisms such as Lamarckism were being proposed. The French zoologist Jean-Baptiste Lamarck (1744–1829) himself accepted the idea, and it had a central role in his theory of inheritance of acquired characteristics, the hypothesized mechanism of which resembled the "mysterious inner force" of orthogenesis. Orthogenesis was particularly accepted by paleontologists who saw in their fossils a directional change, and in invertebrate paleontology thought there was a gradual and constant directional change. Those who accepted orthogenesis in this way, however, did not necessarily accept that the mechanism that drove orthogenesis was teleological (had a definite goal). Charles Darwin himself rarely used the term "evolution" now so commonly used to describe his theory, because the term was strongly associated with orthogenesis, as had been common usage since at least 1647. His grandfather, the physician and polymath Erasmus Darwin, was both progressionist and vitalist, seeing "the whole cosmos [as] a living thing propelled by an internal vital force" towards "greater perfection". Robert Chambers, in his popular anonymously published 1844 book Vestiges of the Natural History of Creation presented a sweeping narrative account of cosmic transmutation, culminating in the evolution of humanity. Chambers included detailed analysis of the fossil record.
With Darwin
Ruse observed that "Progress (sic, his capitalisation) became essentially a nineteenth-century belief. It gave meaning to life—it offered inspiration—after the collapse [with Malthus's pessimism and the shock of the French Revolution] of the foundations of the past." The Baltic German biologist Karl Ernst von Baer (1792–1876) argued for an orthogenetic force in nature, reasoning in a review of Darwin's 1859 On the Origin of Species that "Forces which are not directed—so-called blind forces—can never produce order." In 1864, the Swiss anatomist Albert von Kölliker (1817–1905) presented his orthogenetic theory, heterogenesis, arguing for wholly separate lines of descent with no common ancestor. In 1884, the Swiss botanist Carl Nägeli (1817–1891) proposed a version of orthogenesis involving an "inner perfecting principle". Gregor Mendel died that same year; Nägeli, who proposed that an "idioplasm" transmitted inherited characteristics, dissuaded Mendel from continuing to work on plant genetics. According to Nägeli many evolutionary developments were nonadaptive and variation was internally programmed. Charles Darwin saw this as a serious challenge, replying that "There must be some efficient cause for each slight individual difference", but was unable to provide a specific answer without knowledge of genetics. Further, Darwin was himself somewhat progressionist, believing for example that "Man" was "higher" than the barnacles he studied. Darwin indeed wrote in his 1859 Origin of Species:
In 1898, after studying butterfly coloration, Theodor Eimer (1843–1898) introduced the term orthogenesis with a widely read book, On Orthogenesis: And the Impotence of Natural Selection in Species Formation. Eimer claimed there were trends in evolution with no adaptive significance that would be difficult to explain by natural selection. To supporters of orthogenesis, in some cases species could be led by such trends to extinction. Eimer linked orthogenesis to neo-Lamarckism in his 1890 book Organic Evolution as the Result of the Inheritance of Acquired Characteristics According to the Laws of Organic Growth. He used examples such as the evolution of the horse to argue that evolution had proceeded in a regular single direction that was difficult to explain by random variation. Gould described Eimer as a materialist who rejected any vitalist or teleological approach to orthogenesis, arguing that Eimer's criticism of natural selection was common amongst many evolutionists of his generation; they were searching for alternative mechanisms, as they had come to believe that natural selection could not create new species.
Nineteenth and twentieth centuries
Numerous versions of orthogenesis (see table) have been proposed. Debate centred on whether such theories were scientific, or whether orthogenesis was inherently vitalistic or essentially theological. For example, biologists such as Maynard M. Metcalf (1914), John Merle Coulter (1915), David Starr Jordan (1920) and Charles B. Lipman (1922) claimed evidence for orthogenesis in bacteria, fish populations and plants.John Merle Coulter. (1915). A Suggested Explanation of 'Orthogenesis' in Plants Science, Vol. 42, No. 1094. pp. 859–863. In 1950, the German paleontologist Otto Schindewolf argued that variation tends to move in a predetermined direction. He believed this was purely mechanistic, denying any kind of vitalism, but that evolution occurs due to a periodic cycle of evolutionary processes dictated by factors internal to the organism. In 1964 George Gaylord Simpson argued that orthogenetic theories such as those promulgated by Du Noüy and Sinnott were essentially theology rather than biology.
Though evolution is not progressive, it does sometimes proceed in a linear way, reinforcing characteristics in certain lineages, but such examples are entirely consistent with the modern neo-Darwinian theory of evolution. These examples have sometimes been referred to as orthoselection but are not strictly orthogenetic, and simply appear as linear and constant changes because of environmental and molecular constraints on the direction of change. The term orthoselection was first used by Ludwig Hermann Plate, and was incorporated into the modern synthesis by Julian Huxley and Bernard Rensch.
Recent work has supported the mechanism and existence of mutation biased adaptation, meaning that limited local orthogenesis is now seen as possible.
Theories
For the columns for other philosophies of evolution (i.e., combined theories including any of Lamarckism, Mutationism, Natural selection, and Vitalism), "yes" means that person definitely supports the theory; "no" means explicit opposition to the theory; a blank means the matter is apparently not discussed, not part of the theory.