“Input caterpillar — black box — output butterfly. What happened?” So quips biologist Ann Gauger in the documentary Metamorphosis from Illustra Media. Is the secret in the genes?
Viewers of the film will never forget the story of the Monarch butterfly’s migration. How these delicate flying machines, each weighing less than an ounce, can navigate unerringly 2,000 miles to Mexico without having ever been there, and land on the same trees their great-grandparents visited the year before, remains a profound mystery in biology and one of the most amazing spectacles in nature. Now, their genetic library is giving us a first look into the black box.
A draft genome of the Monarch butterfly was published this year. Scientists at the University of Massachusetts Medical School analyzed the genome for clues. Last week, they published their findings in the journal Cell1 and issued a press release on the UMMS website.
Interesting things did come to light. They found 16,866 protein-coding genes, including “several gene families likely involved in major aspects of the monarch’s seasonal migration.” Surprisingly, the DNA base pair count is 40% smaller than that of the only other lepidopteran genome sequenced so far, the silkworm moth; nevertheless, the Monarch genome “shares prominent similarity in orthology content, microsynteny, and protein family sizes.” The team listed several novel insights about the Monarch’s genes related to the sun compass, circadian clock, orientation, chemical defense, olfactory enhancement, and hormone regulation. Nature’s NewsBlog summarized the findings like this:
Within the new genome, the research team found several gene groupings that help to explain how these insects know where to go. Compared with other sequenced insects, the butterflies had different genetic patterns in visual areas, which might help them to gather cues from the sun to guide their route. The research also found genetic clues about how their circadian clocks differ from those of other animals, which might help these long-distance fliers to respond differently to light during their travels.
“Help… might… might.” It’s clear the findings so far are preliminary and tentative at best, leaving us with more questions than answers. The write-ups in the science media sites spoke primarily in future tense. Science Newsline Biology quoted the team as saying:
Overall, the attributes of the monarch genome and its proteome provide a treasure trove for furthering our understanding of monarch butterfly migration; a solid background for population genetic analyses between migratory and non-migratory populations; and a basis for future genetic comparison of the genes involved in navigation yet to be discovered in other long-distance migrating species, including vertebrates like migratory birds.
But can the whole story be teased out from strands of DNA? “There must be a genetic program underlying the butterflies’ migratory behavior,” Stephen M. Reppert, MD, senior author of the UMMS study, commented in the press release. “We want to know what that program is, and how it works.” Notice that Reppert omitted from his remark the possible role of epigenetic factors. While a genetic program may underlie the Monarch’s uncanny navigational ability, would it be sufficient to explain it?
Thumbnail image for Thumbnail image for Monarch-wildflower.jpgOne clue emerged from the analysis. The abstract states that the team found “microRNAs that are differentially expressed between summer and migratory butterflies,” the so-called “Methuselah generation” that lives ten times longer than its parents and grandparents allowing it to make the trip to Mexico and back to Texas. MicroRNAs do not come from genes, but are short transcripts from DNA that regulate gene expression. This is very interesting, but it begs the question of what governs the phenomenon. What regulates the regulators? Who or what writes and operates the genetic program?
The scientists credit “evolution” as the programmer. The abstract states, “Orthology properties suggest that the Lepidoptera are the fastest evolving insect order yet examined.” This is inferred from the difference in base pair counts between the silkworm moth and Monarch butterfly, and how much time the researchers assume transpired since the common ancestor. Unless the team bucks orthodox belief, they imply by “evolving” that a blind, unguided, purposeless process took the common ancestor’s descendants down different creative pathways. Silkworms developed their silk-spinning specialty, and Monarchs developed exquisite navigational machinery — all by a series of accidental mutations that never had those end goals in mind.
Their explanation is incoherent. On one hand, they assume a genetic program exists. On the other, they assume an unguided process not only led to the wonders of Monarch migration, but wrote the original program and upgraded it. Nothing in our uniform experience supports such speculation. We all know that programmers write programs. We build aircraft and spacecraft that, like butterflies, navigate using environmental cues, but we all know the hardware and software come from intelligence, not from unguided forces. That is one reason why the inference to the best explanation for Monarch migration is intelligent design.