March 21, 2014 | David F. Coppedge

Sticking Evolution to a Stick Insect Fossil

A fossil of a mature stick insect was found in China.  What’s evolution got to do with it?

Live Science and New Scientist show pictures of the oldest known “stick insect,” a leaf mimic that looks like a ginkgo leaf.  New Scientist says it “walked with dinosaurs” 126 million years ago.  The fossil is the latest from the rich Jehol biota of China, where many exquisitely-preserved fossils have been found.  Gingko leaf impressions similar to the insect’s wings were also found.  Ginkgo trees are “living fossils” that had been thought to be extinct since the time of the dinosaurs, but then were found alive and well in China decades ago.  Now, they are among the most popular ornamental trees.

Scientists were determined to stick evolution to this fossil.  Tia Ghose in Live Science said, “The discovery of both specimens suggests the insect had evolved its leaf mimicry— or, more specifically, its gingko-leaf mimicry — to evade hungry predators.”  New Scientist stuck the force on predators: “Their penchant for gobbling up invertebrates may have helped drive the evolution of the stick insect’s plant mimicry.”

Sticking it to butterflies

Speaking of mimicry, another spectacular case is found in swallowtail butterflies, where males imitate bad-tasting species but females do not.  Nature News reported on March 5 that a single regulatory gene, called doublesex (already known for its role in sexual differentiation), acts like a master switch to turn on wing coloration patterns.  This could cause rapid changes in wing coloration in certain spots on the wings, but the doublesex gene itself, the article notes, is “evolutionarily conserved“.  Science Daily has a display of the varied wing patterns in swallowtails with different expression patterns of the genes, but didn’t discuss evolution.  It only described possible ways the patterns are sorted and conserved:

How one gene controls so many different functions remains unclear. Kronforst suggests that noncoding, regulatory DNA that controls when and where doublesex is expressed may play a role. The team also found that in mimetic butterflies, the doublesex gene is inverted on the genome. This inversion eliminates the possibility of recombination — alleles will remain distinct from each other and accumulate differing mutations. This has led to structural differences in the doublesex protein between mimetic and non-mimetic butterflies. Because doublesex is a transcription factor and activates other genes, the researchers believe these differences may also contribute to wing pattern variation.

“We’ve illustrated the genetic basis of female-limited mimicry in these butterflies,” said Wei Zhang, PhD, postdoctoral fellow at the University of Chicago and a lead study author. “But this is just the first step. How doublesex became involved in this process is still uncertain, and requires further study.

With that caveat, it would be premature to say that the evolution of mimicry is understood.

Anyone see evolution here?  You can’t stick it to an insect after the fact.  You can’t say the stick insect “evolved to” avoid predators.  You can’t say the ginkgo tree drove the stick insect to mimic its leaves.   You can’t say butterflies evolved mimicry to avoid being eaten.  The environment and the ecology are powerless to design things.  Dropping a stone into the ocean does not make it evolve fins.  Unless internal programming was pre-designed into the organism by the Creator, as Dr. Randy Guliuzza has explained in detail (ICR), nothing would happen.  Adaptive design, he argues, is part of the Creator’s plan to allow his creatures to fill the Earth, surviving in a wide range of conditions.  That is not “natural selection”; it is pre-design.

The notable things about these stories are (1) abrupt appearance of mimicry, (2) living fossils (the ginkgo), and (3) genes that are “evolutionarily conserved”.  These are all challenges to Darwinian evolution, but supports for intelligent design and creation not that long ago.  Another notable thing in the Science Daily article is Kronforst’s admiration of metamorphosis: “When you look at the wing tissue in a chrysalis five days after it forms the pupa, it’s just a floppy piece of white tissue,” Kronforst said. “But when you look at where doublesex is being manufactured on the wing, it looks just like the future adult wing pattern.”  How that could not evolve is discussed in the highly-recommended documentary, Metamorphosis: The Beauty and Design of Butterflies.



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