Showing posts with label wings. Show all posts
Showing posts with label wings. Show all posts

Monday, March 29, 2010

On The Wings of Evolution

Dan Vergano of ooh-es-ahh-heute (USAToday) has a story on how wings may have evolved in insects. They plainly have creationists in the cross-hairs:
Wings allowed bugs to become the most widespread critters on Earth, about three-quarters of all animals, but the fossil record offers no clues to their origin. Wings probably already graced the oldest known insect fossil, Rhyniognatha hirsti, about 400 million years ago.

Some religious writers — such as Matthew Vanhorn of Apologetics Press in Montgomery, Ala., who wrote that the "evolution of insect wings and subsequent flight is a concept impossible for evolutionists to explain" in a 2004 essay on the topic — have seen holes in evolutionary biology in the lack of an insect wing explanation.

But it turns out that just two genes may explain insect wings, reports a team led by Japan's Nao Niwa of the RIKEN Center for Developmental Biology in Kobe.
According to the story, the authors used mayflies and wingless bristletail insects, which are considered to be more primitive in their genetic makeup when compared to animals like butterflies. Here is what they found:
A gene called "vestigial" and another called "wingless" (so named because it prevents wing growth when mutated in fruit flies) work together during the insects' embryonic growth to sprout wings in mayflies, and fail to fire up in the silverfish.

Both genes already were present in the wingless ancient ancestor of today's flying bugs, the researchers note, because they had other jobs to do. One plays a role in development of body shell sheets (vestigial) and the other helps limb growth (wingless). Add them together and you have a shelled limb — a wing, they conclude.
This is still a bit sketchy but it is a workable, testable model for examining this aspect of evolution.

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Sunday, May 17, 2009

Acts & Fiction

The new ICR Acts & Facts magazine has several interesting columns in. One of them is Galapagos: Showcase for Creation, written by John Morris, the son of the late Henry Morris, head of the ICR. In it, he writes:
The Santa Cruz River was the Beagle's first major stop, and thus Darwin's first chance to apply Lyell's ideas. Dr. Austin discovered Darwin had made numerous errors in Argentina as he attempted to interpret the river valley according to uniformity, and mistook major Ice Age flooding for great ages of minor processes.
Of course, Dr. Morris does not say what these errors were, just that Darwin made them. You have to go to another article, Darwin's First Wrong Turn, by Steven Austin to get that information. In that article, Austin suggests that Darwin misidentified part of a section of the river bank as a basalt flow. Austin states that it cannot be a basalt flow but must, instead, be the remains of a catastrophic flood channel. Austin writes:
Why was Darwin so wrong concerning his interpretation of the river valley? First, he had expectations about what he would see at Camp Darwin before he arrived. His scientific judgment was tainted by preconceptions. Second, Darwin was reading the wrong book before his journey up the Santa Cruz River valley. He had been reading Charles Lyell's book Principles of Geology (1830) during his trans-Atlantic voyage on the Beagle. That book gave him the idea that the biggest boulders were deposited from melting icebergs.
Austin provides no evidence that the deposits were not the remains of a melting glacier. He simply says that there had to have been a colossal flood. Back to Morris. He writes that Darwin observed the finches on the Galapagos Islands and applied natural selection to them. Of this, Morris states:
Evolutionists trumpet the several Galapagos finch "species" as arising by adaptation from one species. Creationists agree, but this did not happen through evolution. Normally the finch types segregate by lifestyle according to their beak shape, but in times of stress they interbreed and combine. No evolution here. The flightless cormorants are recognizably related to other species of cormorant on other continents, but these have lost the use of their wings. Since when is the loss of a useful structure an evolutionary development? The real question is how animals acquire wings in the first place, not how they lose them.
Darwin correctly observed that the finches in different islands looked different and that their beaks were different. In other words, they had adapted to their environments. What is this an example of? Evolution. How did flightless cormorants lose the use of their wings? Evolution, that's how. Descent with modification. This could happen any number of different ways. For example, a small population may have broken off in which a mutation for flightless wings was present. In small populations, this trait would have expressed itself. In the presence of no selection in favor of flight, the trait would eventually permeate the population. The fact that flightless cormorants exist at all means that they can survive just fine without wings that fly. There may have been another reason why they retained the wings but not the ability to fly with them. Wings make great insulators. In the Liaoning fossil beds in China, researchers are discovering flightless dinosaurs that had wings. And that, by the way, is how they acquire wings in the first place. Any time you have descent with modification, you have evolution going on. More fiction from the ICR.