Devolution (biology)

Devolution, de-evolution, or backward evolution (not to be confused with <a href="/facts/Dysgenics/lE7Q5326">dysgenics</a>) is the notion that <a href="/facts/Species/oDg6b96r">species</a> can revert to supposedly more <a href="/facts/Primitive_(phylogenetics)/PqDfhuWm">primitive</a> forms over time. The concept relates to the idea that <a href="/facts/Evolution/qE5amP6a">evolution</a> has a divine purpose (<a href="/facts/Teleology/8YR2sPUf">teleology</a>) and is thus progressive (<a href="/facts/Orthogenesis/TKjwUPmA">orthogenesis</a>), for example that <a href="/facts/Feet/gnX2RTz7">feet</a> might be better than <a href="/facts/Hoof/akrIlYRN">hooves</a>, or <a href="/facts/Lung/gTWXI6Fj">lungs</a> than <a href="/facts/Gill/FWgM3Jp8">gills</a>. However, <a href="/facts/Evolutionary_biology/8tBoG55U">evolutionary biology</a> makes no such assumptions, and <a href="/facts/Natural_selection/JXTte6en">natural selection</a> shapes <a href="/facts/Adaptation/5K2gNpDB">adaptations</a> with no foreknowledge or foresights of any kind regarding the outcome. It is possible for small changes (such as in the frequency of a single gene) to be reversed by chance or selection, but this is no different from the normal course of evolution and as such de-evolution is not compatible with a proper understanding of evolution due to natural selection.
In the 19th century, when belief in orthogenesis was widespread, zoologists such as <a href="/facts/Ray_Lankester/sffTH0xV">Ray Lankester</a> and <a href="/facts/Anton_Dohrn/VoEpClED">Anton Dohrn</a> and palaeontologists <a href="/facts/Alpheus_Hyatt/QALp0NHx">Alpheus Hyatt</a> and <a href="/facts/Carl_H._Eigenmann/vW2u8Gv1">Carl H. Eigenmann</a> advocated the idea of devolution. The concept appears in <a href="/facts/Kurt_Vonnegut/sPmWap62">Kurt Vonnegut</a>'s 1985 novel <a href="/facts/Gal%25C3%25A1pagos_(novel)/UjnRIc3H">Galápagos</a>, which portrays a society that has evolved backwards to have small <a href="/facts/Brain/Xo5ABfXl">brains</a>.
<a href="/facts/Dollo%2527s_law_of_irreversibility/yMQ1smNq">Dollo's law of irreversibility</a>, first stated in 1893 by the palaeontologist <a href="/facts/Louis_Dollo/nVF5SmcQ">Louis Dollo</a>, denies the possibility of devolution. The evolutionary biologist <a href="/facts/Richard_Dawkins/x8Q24PJG">Richard Dawkins</a> explains Dollo's law as being simply a statement about the <a href="/facts/Probability/fgYvMhwb">improbability</a> of evolution's following precisely the same path twice.

Devolution (biology) open-in-new

Devolution (biology)