Lou FCD
Posts: 5455
Joined: Jan. 2006
|
That's worth saving so just in case:
| Quote (Jud @ Jan 1st 2007,6:14 pm) |
6. Jud // Jan 1st 2007 at 6:14 pm
DaveScot said that Carl Zimmer’s article supported the notion that genotype and phenotype are “increasingly at odds” with regard to proper characterization of the ancestry of various animals. I disagreed, noting Zimmer’s article actually illustrated the coming together in agreement of biologists championing phenotype with those researching primarily in the area of genotype.
DaveScot quoted a portion of Zimmer’s article in support of his statement. In support of my interpretation of what the article says, let me quote another segment of it. Apologies for the length, but I feel it’s necessary:
“At the time, molecular phylogenies were still a novelty. The computational methods for calculating them were relatively new, and scientists could only use them to compare a few gene sequences of whales and other mammals. But the conclusions from these few studies were the same: the closest living cousins of whales are hippos.
“This may not seem like a big deal. It certainly didn’t seem to bother the scientists who carried out the studies. They were just analyzing digital code, abstracted from the animals that carried it. The results spoke for themselves. Nevertheless, they gave paleontologists and mammalian systematists conniptions.
“Here’s why. Hippos are artiodactyls (also known as even-toed ungulates). Other artiodactyls include cows, camels, and pigs, and goats. Zoologists have long recognized a number of anatomical features that unite artiodactyls in their own group, distinct from other hoofed mammals such as horses and rhinos. One of the most obvious hallmarks was a bone in the ankle, the astragalus. The artiodactyl astragalus has a unique double-pulley shape that allows the artiodactyl hoof to swing back and forth in a distinctive way.
“In the 1990s paleontologists found a number of spectacular early whale fossils, but they had yet to find bones from the whale ankle. The bones and teeth they did find suggested that the closest relatives of whales were an extinct group of mammals called mesonychids. Mesonychids were hoofed mammals, but they did not have a double-pulley astragalus. Therefore, paleontologists concluded, they were probably not artiodactyls. And if mesonychids were not artiodactyls, then whales could not be either. And that meant that the whale–hippo link had to be wrong.”
* * *
“Subsequent studies on mammal DNA continued to support the whale–hippo link. And meanwhile paleontologists discovered more fossils of ancient walking whales. In 2001 Phil Gingerich and his colleagues from the University of Michigan and from Pakistan described a skeleton of the seal-like species Rodhocetus. Among its bones, they found an astragulus—the first whale astragulus ever discovered. And lo and behold, the astragalus had a double-pulley shape [citation omitted]. The DNA, it seems, had been right all along.”
So biologists started out in disagreement - DNA indicated artiodactyls, the fossils seemed to point to mesonychids. However, later fossil finds confirmed whale ancestors were artiodactyls, the same line from which hippos came. Thus, Zimmer’s article points out that phenotype was found to agree with genotype.
Therefore, I can’t agree that Zimmer’s article supports the notion that genotype and phenotype are “increasingly at odds.”
Comment by Jud — January 1, 2007 @ 6:14 pm
|
--------------
“Why do creationists have such a hard time with commas?
Linky“. ~ Steve Story, Legend
|
