Dollo's law of irreversibility

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Once an organism has evolved in a certain way, it will not return exactly to a previous form. This is illustrated here in two dimensions; in reality, both biomolecules and organisms evolve in many different dimensions.

Dollo's law of irreversibility (also known as Dollo's law and Dollo's principle), proposed in 1893[1] by Belgian paleontologist Louis Dollo states that, "an organism never returns exactly to a former state, even if it finds itself placed in conditions of existence identical to those in which it has previously lived ... it always keeps some trace of the intermediate stages through which it has passed."[2]

The statement is often misinterpreted as claiming that evolution is not reversible,

irreversibility forecloses certain evolutionary pathways once broad forms have emerged: "[For example], once you adopt the ordinary body plan of a reptile, hundreds of options are forever closed, and future possibilities must unfold within the limits of inherited design."[7]

This principle is classically applied to

mutations
or gene losses.

Use in phylogenetics

In

seahorses, among others.[9]

This also applies to molecular characters, such as losses or

gulonolactone oxidase, the final enzyme in the biosynthetic pathway of vitamin C, is responsible for the dietary requirement of vitamin C in humans, as well as many other animals.[11]

A molecular example

A 2009 study on the evolution of protein structure proposed a new mechanism for Dollo's law. It examined a hormone receptor that had evolved from an ancestral protein that was able to bind two hormones to a new protein that was specific for a single hormone. This change was produced by two amino acid substitutions, which prevent binding of the second hormone. However, several other changes subsequently occurred, which were selectively neutral as they did not affect hormone binding. When the authors tried to revert the protein back to its ancestral state by mutating the two "binding residues", they found the other changes had destabilised the ancestral state of the protein. They concluded that in order for this protein to evolve in reverse and regain its ability to bind two hormones, several independent neutral mutations would have to occur purely by chance with no selection pressure. As this is extremely unlikely, it may explain why evolution tends to run in one direction.[12]

Proposed exceptions

Although the exact threshold for violations of Dollo's law is unclear, there are several case studies whose results dispute the validity of some interpretations. For example, many taxa of

gastropods have reduced shells, and some have lost coiling of their shell altogether.[13] In Stephen Jay Gould's interpretation of Dollo's law, it would not be possible to regain a coiled shell after the coiling has been lost. Nevertheless, a few genera in the slipper snail family (Calyptraeidae) may have changed their developmental timing (heterochrony) and regained a coiled shell from a limpet-like shell.[13][14] Frietson Galis observed that many of these studies are based on either molecular phylogenies or morphological cladistic analyses that are tenuous and subject to change.[15]

Other proposed 'exceptions' include the

theropod dinosaurs,[23] and neck, pectoral region, and upper limb musculature in primates, including the lineage leading to humans.[24]

See also

References

  1. ^ Dollo, Louis (1893). "Les lois de l'évolution" (PDF). Bull. Soc. Belge Geol. Pal. Hydr. VII: 164–166.
  2. S2CID 45642853
    .
  3. PMID 24310356
    .
  4. S2CID 30703407
    .
  5. PMID 18814933
    .
  6. ISBN 978-0-393-31570-7
    .
  7. ISBN 978-0-09-950744-4
    .
  8. doi:10.1093/sysbio/26.1.77
    .
  9. PMID 27974754
    .
  10. ISBN 9780199297306. {{cite book}}: |journal= ignored (help
    )
  11. S2CID 14393449
    .
  12. PMID 19779450
    .
  13. ^
    PMID 14728776
    .
  14. PMID 16701270
    .
  15. ^ Alan Feduccia: Riddle of the Feathered Dragons: Hidden Birds of China, Yale University Press, 2012.
  16. S2CID 962571
    .
  17. PMID 35549660
    .
  18. ^ Chippindale, P. T.; Wiens, J. J. (2005). "Re-evolution of the larval stage in the Plethodontid salamander genus Desmognathus" (PDF). Herpetological Review. 36 (2): 113–117.
  19. PMID 7991619
    .
  20. S2CID 24520027
    .
  21. S2CID 3553000
    .
  22. ^ Davies, E. Frogs re-evolved lost lower teeth. BBC News. January 31, 2011. Retrieved February 9, 2011.
  23. ISBN 978-0-8018-6763-7
    .
  24. S2CID 21754061
    .

External links
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