January 6, 2009 | David F. Coppedge

Darwin Missed the Pink Iguanas

The news media are excited about pink iguanas found in the Galapagos Islands.  The rare type was discovered accidentally in 1986 but received almost no attention till now.  Reports with pictures can be found on Live Science, PhysOrg, New Scientist and the BBC News, based on the paper by Gentile et al in PNAS.1
    The “rosada” (pink) land iguana is similar in size and shape to a more common yellow variety on Isabela island, the largest island in the Galapagos archipelago.  Darwin did not see any of these during his five-week tour.  It is surprising no other scientist saw this population, either, for 150 years after Darwin’s stopover.  They live isolated on an extinct volcano named Volcan Wolf on the north end of Isabela island.
    The scientists performed phylogenetic analysis of individuals and declared them to be the most basal land iguanas on the islands.  They estimate they diverged 5.7 million years ago and went their own way genetically.  This raises a conundrum, however; the island of Isabela, their sole habitat, did not form till half a million years ago, they believe.  How did the pink form remain genetically isolated for so long when the populations were free to mix with others?  Actually, they were found not to be completely isolated.  One yellow iguana appeared to have a rosada grandparent, so hybridization, though rare, does occur (as it does with the finches).  “In any case, incomplete reproductive isolation between the rosada and syntopic yellow land forms is not surprising,” they said, “considering that hybridization can still occur between marine and land iguanas, 2 genera morphologically, ecologically, behaviorally, and genetically very distant.

1.  Gentile et al, “An overlooked pink species of land iguana in the Galapagos,” Proceedings of the National Academy of Sciences USA, published online before print January 5, 2009, doi: 10.1073/pnas.0806339106.

Is this evolution?  They look nearly identical to the other land iguanas except for skin color and slight differences in head-bobbing behavior.  There are more differences between people than between these iguanas.  To be told that they have been genetically isolated ten times longer than the island they live on was separated from the others is a stretch; it’s also not very helpful to evolutionary theory, because they believe humans came down from the trees and evolved philosophy in less time than that.
    Phylogenetic analysis is fraught with dubious assumptions.  Differences this small can take a lot less time to develop.  Live Science quoted the lead author saying, “The Darwin finches are thought to have differentiated later than the split between the pink and yellow iguana lineages.”  And just like the finches, the differences are minor variations.  No new genetic information, tissues or organs “emerged” by Darwin’s mechanism.
    The news write-ups, nevertheless, are filled with references to Charlie.  King Charles had nothing to do with this.  He didn’t even see them.  He came up with a tall tale after his voyage about how humans might have had bacteria ancestors.  Why?  Because he saw microevolutionary changes in finches, turtles, mockingbirds and cacti in an isolated, desolate environment, and could not fit these observations into preconceived theological notions about how God would have done things.  For this Charlie should be scorned, not praised.
    Darwin’s name would not be remembered except for his visit here, his 200th birthday coming up, and the pressure of his disciples to associate his name with these islands that are full of amazingly hardy, well-adapted, created creatures (redundant, since creature refers to a created living thing).  All creatures of our God and King was not written in praise of King Charlie, despite the devotion of his subjects.

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Categories: Terrestrial Zoology

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