De-evolution or devolution is a theory that a species is actually evolving backward. This is often favored by Biblical literalists who like to view Adam and Eve as perfect beings who were created, and that the human race has "devolved" from them. De-evolution is sometimes formalized by the assertion that all mutations destroy information, rather than create information.
The term is also used by cynics and misanthropes to refer to the perceived increasing dominance of the stupid.
 Applicability to evolution
The term "devolution" is sort of a misnomer as evolution and natural selection do not have a definitive path forward so there can't really be backward evolution - evolutionary theory states that evolution is an unguided process. As a result, the concept is usually a plea to emotional attachment that humans may have for their own perceived superiority. In the cold, reasoned light of science, however, such a notion doesn't hold, and unguided evolution - neither forward nor backward - is the dominant theory.
If changes to a species were specifically controlled in a way that each change was reversed in order, it might be accurate to call the act "devolution", but this would require a perfect history of the organisms genetic makeup by each generation and a flawless mean to control the changes. This would make for excellent research into genetics... were that knowledge not already necessary for such exotic manipulations. Even so, this is no more "un-evolving" something than flattening Play Doh into a pancake and rolling it back into a ball is "un-pancaking".
The concept of devolution is similar to that of "dysgenics," in which eugenicists bemoaned the decline of humanity as the rabble were supposedly outbreeding the better stock.
Consider a cave-living fish which loses its power of sight because it is not needed in dark conditions where sight is useless anyway. Believers in de-evolution would cite this as a prime example of an ability is lost, possibly forever, and devolution from the perfection of creation in action. However, considering the reality of evolution guided only by external, environmental pressures, this interpretation makes little sense and the adaptation of sight being lost can be thought of more generally; looking at what survival advantages such an adaptation may allow. Sight is no longer necessary to this example fish, so the evolutionary process has no reason to preserve it - fish born without sight would be at no-specific disadvantage compared to their sighted counterparts. In fact, the blind fish now has a better chance of survival and reproduction compared to its sighted colleagues, which waste energy on a very unnecessary function that exposes them to infection and injury. The blind fish has become better adapted to its present surroundings - it has not "devolved".
Similarly, those citing humanity's loss of agility, sight, or overall fitness when compared to ancestors don't take into account the increased mental capabilities (shown by inflation of IQ over time, for instance) as time goes on, which allows for increases in technology and medicine that prolong life and survivability better than standard physical capabilities would. In fact, there is a bias held by many people that humanity will continue to "evolve" into a more intelligent being - but there is no biological reason for this to be so. If less intelligent people were favoured by natural selection, or if they were more liable to reproduce for some reason, then humanity would would move in the direction of having less intelligence.
The term was popularized by the band Devo (the name itself is a reference to de-evolution) in their song "Jocko Homo." The singer repeatedly asks "Are we not men?" to which the others reply "We are Devo!"
 Cretinism (sic)
 De-evolution in science fiction
The concept of de-evolution occasionally shows up in science fiction. It usually happens when the heroes (usually humans) land on a distant planet. The planet is filled with sophisticated technology (often in the form of ruins), but the species who built this technology no longer has the intelligence to replicate it. The conclusion that the heroes reach is that the species which built the technology has "devolved" into a more stupid form. 
This shows a strong anthropocentrically biased view of evolution. While it is possible that an intelligent species could, over the course of evolutionary time, become less intelligent, it would presumably be because (like the sightless cave fish) the energy they spent on building brains could be better spent on, say, improving their jaw strength, or resisting nuclear radiation, or what have you. This is not "de-evolution" -- it is "evolution in a direction away from human ideals".
De-evolution is rock 'n' roll:
 Vedic creationism
 See also
- ↑ This is then used as a springboard to talk about the human race through the miracle of analogies.
- ↑ Science & Religion: A New Introduction, Alister E. McGrath, 2009, p. 140
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