Saturday, June 24, 2017

Evolution Of Flightless Cormorants? - Seriously?

HOW FLIGHTLESS CORMORANTS EVOLVED, according to reports in Science News and UCLA News 1 June 2017, and Science doi:10.1126/science.aal3345, 2 June 2017. The Galapagos cormorant, Phalacrocorax harrisi, has short stubby wings and a small sternum (breast bone), and is the world’s only flightless cormorant. Flightless birds have intrigued evolutionary biologists from Darwin onwards. An international group of scientists has conducted a study of the genomes of Galapagos cormorants and other cormorants in order to understand how flightless birds evolved. The reason for studying these particular flightless birds is described by Science News: “Unlike penguins, ostriches, kiwis, and emus—which evolved into their flightless forms more than 50 million years ago—the Galapagos cormorant (Phalacrocorax harrisi) diverged from its soaring relatives a mere 2 million years ago. That more recent split suggests a relatively small number of genetic changes differentiate high-flying cormorants from their land-lubber cousins.” The researchers’ report in Science is entitled “A genetic signature of the evolution of loss of flight in the Galapagos cormorant” and in their introduction they comment “Darwin used the occurrence of flightless birds as an argument in favour of his theory of natural selection. Loss of flight has evolved repeatedly and is found among 26 families of birds in 17 different orders”. They continued: “To better understand the evolution of changes in limb size, we studied a classic case of recent loss of flight in the Galapagos cormorant (Phalacrocorax harrisi)”. The scientists compared the genome of the flightless cormorants with those of three other cormorant species, and found the flightless cormorant has a number of gene mutations similar to those found in humans who suffer from rare bone deformities known as skeletal ciliopathies, which results in shortened limbs and abnormalities of the rib cage. They tested the effects of one of the genes, named Cux1, by inserting the flightless cormorant’s version into cartilage cells growing in a cell culture. The mutated cells showed stunted development. All the mutated genes they found interfere with the proper functioning of primary cilia – hair-like protrusions from cells, whose function is important in controlling bone and cartilage growth during embryonic development. The researchers admit their study has not yet proved these gene mutations caused the birds to become flightless. Geneticist Leonid Kruglyak who was involved in the study, explained: “The ideal experiment would make a Galapagos cormorant fly or another cormorant not fly”. This may become possible with new genetic engineering techniques. Kruglyak went on to say, “As technologies improve, we can imagine testing these gene mutations in birds and watching the wings develop”.
Links:
Science, UCLA

ED. COM These studies of cormorant genes certainly do indicate that flightless cormorants are descended from flying cormorants, but they have not evolved any more than people who suffer with limb loss via skeletal ciliopathies can say they have evolved. These deformities are a loss of structure and function. If these newly discovered gene variants turn out to be the reason Galapagos cormorants can’t fly, they simply confirm that flightlessness is the result of loss of function, i.e. it is degeneration, not evolution. We predict the same kind of genetic defects should be found in other flightless birds such as the NZ Kakapo (a parrot) and the Titicaca Flightless Grebe, which have similar loss of structure in their wings, muscles and bones. However, these studies do not explain the origin of large flightless birds such as penguins, ostriches, and emus, and hiding behind millions of years doesn’t help either. All studies of living and fossil penguins, ostriches and emus indicate they have never had wings and are well designed functional creatures that were never meant to fly. They use their wings for other functions, such as swimming, balance and thermoregulation. If technology does advance enough for Kruglyak to carry out his genetic engineering experiments it still will confirm degeneration of genes caused loss of flight, and will not prove any evolutionary theories. If scientists were able to make flightless cormorants fly by giving them genes deliberately taken from a flying species, they will prove that it takes intelligent understanding of genetic information as well as clever manipulation, to turn a non-flying bird into a flying bird.
Illustration: Galapagos Cormorant. Photo by Paul McFarling, Charles Darwin Foundation. Licensed under Creative Commons + CC BY-NC-SA 3.0