January 11, 2008 | David F. Coppedge

Monarch Butterflies as a Test of Evolution

The Discovery Institute and the National Academy of Sciences have recently published books with butterflies prominently displayed on the cover.  The two books give opposite viewpoints on whether life was designed or a product of evolution.  Maybe a look at a real-world butterfly research project can shed light on the debate.
    A paper in PLoS Biology studied the clock mechanism behind the migrating Monarch butterfly.1  A team from the University of Massachusetts Medical School, with an entomologist from the Czech Academy of Sciences, investigated the proteins that compose the butterfly’s circadian clock.  These proteins, called cryptochromes, are part of a feedback mechanism that takes input from the sun and acts as a time-compensated sun compass.  Remarkably, two of the proteins seem to come from different families: CRY1 is invertebrate-like, and CRY2 is vertebrate-like.  They summarized their findings as follows:

Collectively, our results provide several lines of evidence suggesting that monarch CRY1 functions in vivo as a circadian photoreceptor, whereas CRY2 functions as a transcriptional repressor for the butterfly clockwork.  This novel clock mechanism has aspects of both the Drosophila and mouse circadian clocks rolled into one, as well as unique aspects of its own.

The paper used the word novel quite a few times to describe this mechanism: i.e., “The results define a novel, CRY-centric clock mechanism in the monarch in which CRY1 likely functions as a blue-light photoreceptor for entrainment, whereas CRY2 functions within the clockwork as the transcriptional repressor of a negative transcriptional feedback loop.”
    Did evolutionary theory provide any of the motivation behind this paper?  Did it offer explanatory power?  Only one instance of the word could be found:

Further molecular evolutionary studies have shown that gene duplication and loss have led to three modes of cry gene expression in insects, giving rise to three types of circadian clocks: two derived clocks, in which only cry1 (e.g., Drosophila) or cry2 (e.g., the honey bee Apis mellifera and red flour beetle Tribolium castaneum) is expressed, and an ancestral clock in which both cry1 and cry2 are expressed (e.g., the monarch butterfly).  The expression of two functionally distinct crys in monarchs suggests that the butterfly clock may use a novel clockwork mechanism that is not yet fully described in any organism.

Yet this refers to other papers, not this one.  It merely assumes that another research team got it right when they used circumstantial evidence to associate genes and transcription patterns with presumed gene-duplication events.  The authors did not find an evolutionary pattern themselves; instead, it is clear that what they found was a novel mechanism dissimilar to that in any other organism.  Functionally speaking, bees and beetles have different lifestyles.  They do not migrate thousands of miles to a particular spot in Mexico.
    In short, the single reference to evolution seemed tacked-on.  It provided neither motivation nor an explanation of the question: how the monarch butterfly arrived at a novel solution to the problem of managing a time-compensated sun compass that allows it to migrate successfully over long distances.  Furthermore, an evolutionary conundrum was evident in the data: “The role of monarch CRY2 as a transcriptional repressor is similar to the role of the CRYs in the mouse clockwork.”  The authors did not begin to explain why the butterfly protein resembles that of a vertebrate with which it has no obvious evolutionary connection, except through some remote, imaginary common ancestor that neither migrated to Mexico nor explored kitchens at night looking for cheese.  Evolution did not explain how clockwork mechanisms arose in the first place, nor why two species with very different evolutionary trajectories would converge on similar designs.
    Did intelligent design provide any input to this research?  The authors did not use that phrase, of course, but engineering language pervaded the paper.  “Clock mechanism” was one of the most common phrases in the paper – a term that raises the ghost of William Paley.  Consider also terms like autoregulatory transcription feedback loop, circadian photoreceptor, and transcriptional repressor.  These all related to engineering functions within a complex system.  Indeed function was another of the most common words in the paper.
    As to motivation for this research, a desire to reverse-engineer a complex system seemed to be the driving force – not a desire to figure out how it evolved.  The “spectacular fall migration” of these insects is a present-day observational fact that drove these scientists to investigate, in detail, how it is accomplished.  “The monarch clock may be the prototype of a clock mechanism shared by other invertebrates that express both CRY proteins,” the Author’s Summary states, “and its elucidation will help crack the code of sun compass orientation.”
    This paper was summarized on National Geographic News.  Here, too, evolution was only in the shadows.  The focus was on understanding a remarkable system.  The motivation is clear in a quote by Stephen M. Reppert, one of the team members: “A butterfly’s brain is no bigger than the head of a pin, and yet it has this incredible capability.  So we really want to understand that.”

1.  Zhu, Sauman et al, “Cryptochromes Define a Novel Circadian Clock Mechanism in Monarch Butterflies That May Underlie Sun Compass Navigation,” Public Library of Science: Biology, Vol. 6, No. 1, e4 doi:10.1371/journal.pbio.0060004.

Discoveries like this are usually made by knocking out genes and watching what happens, or making proteins fluoresce green so they can be followed.  Imagine trying to study a car by knocking out parts to see what breaks.  Take out the oxygen sensor, or the PCV valve, or whatever; is this the best way to understand a system?  What is coming is systems biology in which each part is studied in relation to the whole.  Only by seeing the system in its functional entirety can you understand the contribution of the parts.
    Even so, there is a gap in understanding still.  How can a protein molecule help a butterfly migrate thousands of miles, some of it over trackless ocean, and arrive at a precise mountain in Mexico it has never seen?  Something is missing even if we were to thoroughly understand how each part works.  If you were to step inside a human brain and see all the neurons firing and chemoreceptors operating, you would still be ignorant of what the person was thinking.  Can the spectacular flight of Monarch butterflies be reduced to the action of proteins and genes?  The question underscores the mind-body problem, a philosophical puzzle unsolveable by reductionist science.
    In theory, nothing in biology makes sense except in the light of evolution.  In practice, biology is the study of complex systems that give the appearance of intelligent design.  It gives you butterflies just thinking about all the wonders in nature that showcase design.  Evolutionary theory provides nothing but fluff after the work is done, fluttering about to satisfy the religion of certain people that everything in the world must have a materialist explanation.  Get real: science is an intelligently designed activity by intelligently designed humans studying intelligently designed phenomena.  What’s evol got to do with it?

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