Thursday, June 15, 2017

The Genetics of Flightless Cormorants as Evidence of Evolution


The flightless cormorant is found only in the Galapagos Islands and only on the coastlines of the two most western islands--Fernandina and Isabela--which are also the youngest islands geologically, with the most active volcanoes.  Charles Darwin would surely have been fascinated by them, because he used the occurrence of flightless birds as something best explained by his theory of natural selection. But he did not see these flightless birds during his time in the Galapagos, because he did not land on either of these two islands.  I saw them on my first tour of the Galapagos in 2013, on a yacht named Cormorant, and I wrote a post on them.

Flightlessness have evolved many times--in 26 families of birds in 17 different orders.  But other flightless birds like ostriches, kiwis, and penguins do not have close relatives among flying birds because their split from flying birds occurred over 50 million years ago. But the Galapagos flightless cormorant is closely related to other cormorants, from which they split off only about two million years ago.

Cormorants are large water birds that live near coastlines or lakes.  The Galapagos cormorant is the only flightless cormorant among 40 species of cormorants.

To look for the genetic basis of this evolutionary split, Alejandro Burga and his colleagues compared the genomes of flightless cormorants and three closely related species of cormorants to look for the genetic variants influencing the loss of flight.  They concentrated on genes that affect bone growth that might explain the short wings of flightless cormorants (Burga et al. 2017; Cooper 2017). 

They found that a gene called Cux1 and some others influence the growth of cilia.  In single-celled animals, cilia on the surface of cells function in movement.  In birds and mammals, cilia on the surface of cells pick up biochemical signals for bone growth.  Mutations in Cux1 in humans create diseases, called ciliopathies: human beings affected by ciliopathies have small limbs and ribcages.  In the Galapagos cormorants, variations in Cux1 stop bone growth prematurely, so that the wings are too small for flying.  These birds can still live well on land and in the water, and their short wings might help them in swimming underwater as they hunt for food.

This shows how genetic evolution could have created the Galapagos cormorant as a new species of cormorant, without any need for the miraculous intervention of the Creator or the Intelligent Designer.  It was once common for creationists to argue that microevolution within species was possible, but not macroevolution across species.  But now most creationists have expanded microevolution to include the natural evolution of new species from ancestral species, and yet they say this is within the "kinds" created by God.  So they can concede that flightless cormorants evolved as a new species.  Nevertheless, they say, flightless cormorants are still cormorants, and cormorants were one of the "kinds" originally created by God, with the genetic potential for evolutionary radiation into new species of cormorants.

Notice, however, that Cux1 is found in many animals--from single-celled animals to birds and mammals, including human beings.  Darwinian scientists would see this as evidence for the evolution of all "kinds" of animals by common descent from ancient ancestral species, and perhaps ultimately from one or a few primitive forms of life. 

Can the creationists respond by moving the category of "kinds" to ever higher levels of taxonomy?  At one time, creationists identified "kinds" as species.  Now, they say "kinds" could correspond to "families" in modern taxonomy, or even higher levels.

The problem, as Todd Wood and other creation scientists have admitted, is that the biblical Hebrew word min that was translated as "kind" in King James English is an "imprecise term."  If one believes that the Bible is the divinely revealed Word of God, and not a book written by human beings, then one must wonder why God chose to write in such "imprecise" language.  Why did God chose not to precisely explain the genetics of flightless cormorants and other forms of life?

I am reminded of James Madison's comment in Federalist Number 37 on how imprecise language often is: "When the Almighty himself condescends to address mankind in their own language, his meaning, luminous as it must be, is rendered dim and doubtful by the cloudy medium through which it is communicated."

If the Bible is imprecise in its scientific language, perhaps that's because God did not write the Bible as a textbook of science, but rather as a book of salvational history.


Cooper, Kimberly. 2017. "Decoding the Evolution of Species." Science 356: 904-905.

Burga, Alejandro, et al. 2017. "A Genetic Signature of the Evolution of Loss of Flight in the Galapagos Cormorant." Science 356: 921.

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