According to the brilliant conception of the immortal Charles Darwin (1809-1882): Evolution—the transformation of organisms—results from the fixation of useful individual variations provoked by the struggle for existence under the influence of natural selection. All species—animal or plant—which exist or have existed since the appearance of life on earth, must originate via this fundamental law.1
So began “The Laws of Evolution” published in 1893 by Louis Dollo, curator of Belgium’s Royal Museum of Natural History. Dollo was a renowned Belgian paleontologist who gained his reputation for his work on Iguanodon dinosaurs and for the rules he formulated for paleobiology, the study of the biology of fossil life forms.
Interestingly, Harvard University’s eminent paleontologist Stephen Gould contributed to the publishing of Louis Dollo’s Papers on Paleontology and Evolution in 1980, a date that coincides with the period of considerable debate about Gould’s punctuated equilibrium mechanism of evolution. Dollo’s first law of evolution was “that evolution occurred by abrupt leaps,”1 which was also one premise of Gould’s mechanism. Dollo actually proposed three laws based on his field observations that have been influential in framing evolutionary research and theory. He is remembered today for his second law, which bears his name.
Dollo’s Law of Irreversibility
Dollo stated “that an organism cannot return, even partially, to a previous state already realized in its ancestral series.”1 Today, this is known as Dollo’s law of irreversibility. Accordingly, most evolutionists believe that evolution simply proceeds forward. For organisms with a membrane-bound nucleus, they hold that the operation of natural processes is sufficient to account for the diversity of the organisms’ genes and traits. They believe there is no specific course that evolution is ordained to follow, but once it proceeds, there is essentially no “reverse evolution.”
Paleontological discoveries and theory have not remained static since Dollo formulated his law. The principle of irreversibility has nevertheless been preserved, though interpretations of findings underlying Dollo’s law have changed and the rationale for it has been modified. Those currently believing in irreversibility do not appeal to an abundance of observations. Rather, the belief is justified by the mathematical improbability of a single evolving lineage proceeding and reversing (and re-proceeding) along the same path. Richard Dawkins notes:
“Dollo’s Law” states that evolution is irreversible….Dollo’s Law is really just a statement about the statistical improbability of following exactly the same evolutionary trajectory twice (or, indeed, any particular trajectory), in either direction.2
Gould agrees with this understanding. He says:
Thus, for example, Dollo’s law of irreversibility…only restates the general principles of mathematical probability for the specific case of temporal changes based on large numbers of relatively independent components.3
Of course, if re-evolution is prohibited by the exceedingly low probability of a blind process acting on random mutations in this manner, one could ask why such claims wouldn’t also apply to evolution itself.
Does Dollo’s law deserve the status of scientific law, regardless of the rationale currently invoked to support it? Scientific “law” conveys a very high level of confidence that the principle(s) embodied in the law accurately conform to reality. The status of being called a scientific law is obtained after repeated observations and experiments consistently confirm its principles. True laws are so consistent that any violation of them would constitute a miracle. If Dollo’s law is actually repeatedly violated, then that would constitute a major mistake in evolutionary theory. And it would be a blunder that has been reiterated in evolutionary education for decades.
Dollo’s Blunder: Traits Do Reappear
If organisms break scientific laws, then it is the law that needs a trial, not the organism. Several researchers have conducted that trial. One evolutionary biologist stated, “Recent phylogenetic studies have revealed several potential examples in which Dollo’s law seems to be violated, where lost structures appear to have been regained over evolutionary time.” He found mandibular teeth in one lineage of frogs that re-appeared after being lost, he believes, for about 220 million years. He claims this “shows that there is no support for the model of irreversible evolution (Dollo’s law).”4
Several 2016 papers deal with evolutionary reversals contrary to Dollo. “Single evolutionary reversals occur when a character changes from an ancestral state to a derived state and then back to the ancestral state within a single lineage,” reports University of Hawaii researchers in a study on a native bird species’ beak length. “Multiple reversals extend the process by returning to the derived or ancestral state several times within a single lineage.” The team documents “three single and two multiple reversals of bill length on six main islands from oldest to youngest, consistent with the phylogeny of the lineage.”5
Two other evolutionists hope to treat drug-resistant malaria through various paths of “reverse evolution” back to a susceptible state. Their frustration with thought-limiting concepts surrounding Dollo’s law spilled over:
The lack of a coherent understanding of reverse evolution is partly due to conceptual ambiguity: the term ‘reverse evolution’ is misleading, as it implies directionality in a process (Darwinian evolution) that is near-sighted and agnostic with regard to goal. This has spawned similarly dubious concepts, such as Dollo’s Law, asserting that evolution is intrinsically irreversible.6
Recently, a study documented “loss and reversals” of a molar tooth crest in a lineage of extinct kangaroos after a time gap believed to be 15 million years.7 How can this happen? “We found that contrary to Dollo’s law in biology, features lost in evolution can re-evolve when evolution ‘tinkers’ with the way features are assembled in the embryo,” reported co-researcher Aidan Couzens of Flinders University.8 The report continues how “the researchers argue that ‘reanimating genetically mothballed features may be “allowed” by evolution when it aligns with pressures that determine an animal’s ecology.’” Other true instances of “reverse evolution” may have been missed previously since “biologists have often discounted the potential for evolution to shift into reverse, dismissing such occurrences as convergent evolution, ‘where similar features evolve independently in organisms that are not closely related.’”8
Scientifically “squishy” invocations of evolution “allowing” or “tinkering with” things, coupled with the mental construct of “convergent evolution” and unquantified “ecological pressures,” place Dollo’s law squarely in the mystical realm surrounding evolutionary explanations. Which explains why anyone doing an Internet survey discovers violations of Dollo’s law, including reversals for wings in stick insects, coiling in snail shells, color vision, eggshells in boid snakes, and many more.
Some scientists, however, criticize findings that question Dollo’s law. They defend Dollo by asserting that their phylogenetic trees are superior to “the moderate level of robustness of many phylogenies” in critical studies.9 One researcher allows some latitude for Dollo’s mistake but not for its continued perpetuation. He implies that Dollo made a valid law but not in the sense of criminal law. Rather, it is actually more akin to tax law in that it is has some “loopholes.” Yet, he asserts that the theoretical work of Dollo’s present defenders may have “devastating flaws” of its own.10
An evolutionary law that is violated constitutes a major evolutionary blunder. Possibly Dollo only made a minor blunder in mislabeling an inference as a law, but his overstated and under-supported conjecture misled research for decades. Also, once striking evidences of “re-evolution” were discovered, repeated salvage efforts like classifying them as merely loopholes hinder scientific progress. For example, since Dollo’s law was one element of evolutionary theory that actually was predictive (i.e., that “re-evolution” would not be observed), when observations showed that the prediction was faulty, pursuing non-evolutionary explanations would be sensible—but has frequently not been done.
Overlooking Design-Based Explanations
Perhaps reappearing traits may not be a violation of any law. Nor are they improbability-conquering miracles. This phenomenon is feasibly the outworking of an ingenious design for the purpose of enabling creatures to continually “fill the earth” (Genesis 1:28).
One study on owl monkeys correctly notes that if organisms become too specialized to a niche, then this could “lead to a genetic constraint on adaptation if the environment subsequently changes.”11 In other words, specialization could force organisms down an unrecoverable one-way street. How might human engineers address this issue? For some uses, they may design an entity to stay constrained. In contrast, they may also design mechanisms within self-adjusting entities to turn off in order to go one direction and turn back on to reverse direction. That entity could escape a one-way specialization trap—especially if a trap was assured to happen repeatedly. Do organisms display this turn-off/turn-on characteristic?
Researchers found that after the loss of a structure, in many cases “the genetic and developmental architecture to develop such structures continues to be fully present.”12 Couzens also reviewed how reversibility may be variably widespread among organisms:
It has been argued that trait reversibility may be promoted when there is reutilization of conserved developmental pathways…[and] the reutilization of regulatory pathways and constituent genes is widespread in development…and ancestral states are recoverable across a diverse spectrum of metazoan structures.13
So, many organisms do have mechanisms to allow recovery of ancestral states. These mechanisms remain in place, but they can be deactivated for generations and then reactivated and accessed during embryonic development in other generations. What can explain the persistence of this underlying “developmental architecture” that “reanimates genetically mothballed features”?
Evolutionists claim that the information is “conserved.” Conserved is the evolution-speak label tagged to the phenomenon of finding nearly identical traits across many wildly different organisms. Such organisms supposedly “emerged” from unrelated pathways and carried unchanged (i.e., “conserved”) information for the similar trait across evolutionary time—while many other traits were greatly changing. Finding information for similar traits is certainly a factual observation. But believing that they are “conserved” is a declaration based in imagination…and firm convictions that evolution happened. In contrast, if the common trait is found in only a few diverse creatures, evolutionists then imagine “convergent evolution” happened.
There is a less mystical, more straightforward explanation that is consistent with what engineers do. It may be that different creatures are designed to retain specific developmental architecture for the common purpose of reutilizing regulatory pathways to recover ancestral states when the situation for them is suitable. Stable mechanisms that can be reactivated when useful are more consistent with intelligent forethought since “Darwinian evolution…is near-sighted and agnostic with regard to goal.”14 This may be just one of many incredibly complex innate mechanisms that enable organisms to match their traits to dynamic environmental conditions so they can continually fulfill their God-given mandate to be fruitful, multiply, and fill seas, sky, and Earth (Genesis 1:22, 28).
- Dollo, L. 1893. The Laws of Evolution. Extract from the Bulletin de la Société Belge de Géologie de Paléontologie & D’Hydrologie. 7: 164-166. Emphasis in original.
- Dawkins, R. 1986. The Blind Watchmaker. New York: W. W. Norton & Company, 94. Emphasis in original.
- Gould, S. J. 2002. The Structure of Evolutionary Theory. Cambridge, MA: Harvard University Press, 901-902.
- Wiens, J. J. 2011. Re-evolution of lost mandibular teeth in frogs after more than 200 million years, and re-evaluating Dollo’s Law. Evolution. 65 (5): 1283-1296.
- Freed, L. A., M. C. I. Medeiros, and R. L. Cann. 2016. Multiple Reversals of Bill Length over 1.7 Million Years in a Hawaiian Bird Lineage. The American Naturalist. 187 (3): 363-371.
- Ogbunugafor, C. B. and D. Hartl. 2016. A pivot mutation impedes reverse evolution across an adaptive landscape for drug resistance in Plasmodium vivax. Malaria Journal. 15: 40.
- Couzens, A. M. C. et al. 2016. The role of inhibitory dynamics in the loss and reemergence of macropodoid tooth traits. Evolution. 70 (3): 568-585.
- Kangaroos chew over evolutionary theory. Flinders University news release. Posted on blogs.flinders.edu.au April 18, 2016, accessed April 26, 2016.
- Galis, F., J. W. Arntzen, and R. Lande. 2010. Dollo’s Law and the irreversibility of digit loss in Bachia. Evolution. 64 (8): 2466-2476.
- Wiens, Re-evolution of lost mandibular teeth in frogs, 1292.
- Mundy, N. I. et al. 2016. Can colour vision re-evolve? Variation in the X-linked opsin locus of cathemeral Azara’s owl monkeys (Aotus azarae azarae). Frontiers in Zoology. 13 (1): 9.
- Galis, Dollo’s Law, 2466.
- Couzens, The role of inhibitory dynamics, 568. Emphasis added.
- Ogbunugafor, A pivot mutation impedes reverse evolution.
* Dr. Guliuzza is ICR’s National Representative.