Biological devolution

In common parlance, "devolution" is the notion a species may evolve into more "primitive" forms. From a scientific perspective, devolution does not exist.^[1] Lay people may see evolution as "progress", reflecting the 19th century ideas of Lamarckism and orthogenesis, but modern genetically-based biological evolution theory asserts that evolution occurs by such mechanisms as natural selection , genetic drift, and mutation, and is therefore not directional, forward or backward in time; hence "devolution" is not a valid concept.

It should not be confused with "evo-devo" which is shorthand for evolutionary developmental biology.

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Misconceptions about evolution

• Species evolve because they need to in order to adapt to environmental changes.

Biologists refer to this misconception as teleology, the idea of intrinsic finality that things are "supposed" to be and behave a certain way, and naturally tend to act that way to pursue their own good. As the fossil record demonstrates that more than ninety nine percent of all species that ever lived are now extinct it is clear that most species do not evolve despite radical environmental changes. From a biological viewpoint, when species evolve it is not a reaction to necessity, but rather that the population contains variations with traits that favour their natural selection.

• Evolution means progress to more advanced organisms.

This presumes that there is somehow a preferred hierarchy of structure and function, for example that "feet are better than hooves" or "lungs are better than gills", and can lead to the idea that change to "less advanced" structure can be called "devolution". To biologists this is an aspect of teleology, the supposition that there is purpose or directive principle in the works and processes of nature. A biologist sees all such changes as evolution, since for the organisms possessing the changed structures, each is a useful adaptation to their circumstances. For example, hooves have advantages for running quickly on plains as horses do, and feet have advantages in climbing trees as the ancestors of humans did.

• Humans are the ultimate product or goal of evolution.

This belief is related to anthropocentrism, the idea that human existence is the point of all universal existence, and is a variation on the idea of "progress". To a biologist, describing the biological evolutionary process as goal-oriented would seem as ludicrous as a physicist claiming that the ultimate goal of gravity is to keep the Earth in its present orbit.

• Increasing complexity is the necessary outcome of evolution.

Biologists have evidence of many examples of decreasing complexity in the record of evolution. The lower jaw in fish, reptiles and mammals has seen a decrease in complexity, if measured by the number of bones. Ancestors of modern horses had several toes on each foot; modern horses have a single hoofed toe. Modern humans may be evolving towards never having wisdom teeth, and already have lost the tail found in many other mammals - not to mention other vestigial structures, such as the vermiform appendix or the nictitating membrane.

Use of the term by opponents of evolution

As with other modern sciences, biology is based on a methodological assumption of philosophical naturalism to study and explain the natural world, without assuming the existence or nonexistence of the supernatural. In contrast, creationism and intelligent design are based on teleology in seeking to prove the existence of an organizing principle behind natural laws and phenomena. Opponents of evolution use the teleological argument for the existence of God, and seek to displace evolution as the central organizing concept in biology. To do so, some redefine "evolution" in their terms, and introduce "devolution" to show that evolution theory is incorrect.

Examples include Mastropaulo^[2], who argues that "Change over time, 'definition one' of evolution, actually describes devolution to extinction, the exact opposite of evolution.... actual epidemiological data from human genetic disorders and fatal birth defects, identify 'natural selection,' the alleged 'primary mechanism' for evolution, as actually a mechanism for devolution to extinction, the exact opposite of evolution." and elsewhere^[3], "Evolution is the development of an organism from its chemicals or primitive state to its present state. Devolution is the sequence toward greater simplicity or disappearance or degeneration."

The term has been used in the play Inherit the Wind, the character of Matthew Brady (representative of William Jennings Bryan) using the term to argue that "ape devolved from man", mocking evolutionary theory by offering an alternative he considers just as plausible. In fact, the suggestion of ape degenerating from "man" was brought up by the early young-earth creationist George McReady Price in a work published before the Scopes Trial:

Accordingly, by every just rule of comparison and analogy, we may well declare that if there is any blood relationship between man and the anthropoid apes, it is the latter which have degenerated from the former, instead of the former having developed from the latter. I do not say that this is the true solution of this enigma; but I do say that there is far more scientific evidence in favour of this hypothesis than there ever has been in favour of the long popular theory than man is a developed animal.

—^[4]

The term was also popularized in the late 1970s by the musical group Devo (see Early Years), where it was used (initially) jokingly as a theme by members Gerald Casale and Bob Lewis.

Streamlining evolution

"Devolution", the verb "devolve" and the past participle "devolved" are all common terms in science fiction for changes over time in populations of living things that make them less complex and remove some of their former adaptations. The terminology used herein is nontechnical, but the phenomenon is a real but counter-intuitive one, more accurately known as streamlining evolution. Since the development and maintenance of a feature such as an organ or a metabolite has an energy cost, changes in the environment that reduce the utility of an adaptation may mean that a higher evolutionary fitness is achieved by no longer using the adaptation, thus saving on energy. This requires a mutation that inactivates one or more genes, perhaps by a change to DNA methylation or a methionine codon. Streamlining evolution allows evolution to remove features no longer of much/any use, like scaffolding on a completed bridge. However, "devolution" in practice typically refers to changes that occur from a problem no longer existing rather than superior solutions existing. For instance, of the several hundred known species of animal that live their entire lives in total darkness, most have non-functional eyes rather than no eyes. This is due, for instance, to deterioration of the optic nerve. It occurs because mutations that prevent eye formation have low probability. However several eyeless animal species, such as the Kauai cave wolf spider, living in total darkness whose ancestry mostly had eyes do exist. Together with gene duplication, streamlining evolution makes evolution surprisingly able to produce radical changes, despite being limited to successive, slight modifications.

See also

• Evolution (Korn song)
• Devo
• Dysgenics
• Evolution of complexity
• Great chain of being
• HeLa
• Ulas family

Notes and citations