Image: Matthew Ronshaugen/UCSD
Posted on 02/07/2002 8:49:05 AM PST by realpatriot71
EVOLUTION
Study Hints at How Genetic Mutations Led to Macroevolutionary Change
Image: Matthew Ronshaugen/UCSD |
The fossil record contains numerous examples of dramatic evolutionary change in animals through time. Exactly how genetic alterations brought about these macroevolutionary changes, however, has proved difficult to ascertain. Now new research into the developmental biology of brine shrimp and fruit flies could throw light on the matter. According to a report published online today by the journal Nature, mutations in genes that guide embryonic development allowed insects to develop a radically different body plan from that of their crustacean-like ancestors some 400 million years ago.
The University of California, San Diego, team that conducted the research focused on so-called Hox genes, master switches that turn other genes on and off during the embryonic development of all animals, including humans. One of these Hox genes, known as Hbx, suppresses 100 percent of limb development in the thorax region of fruit flies, but only 15 percent in the brine shrimp Artemia (right). Modifications of Hbx, the investigators determined, would have allowed the many-limbed, crustacean-like ancient relatives of Artemia to lose their rear limbs, giving rise to the six-legged insects. "Before the evolution of insects, the Ubx protein didn't turn off genes required for leg formation," team member William McGinnis explains. "During the early evolution of insects, this gene and the protein it encoded changed so that they now turned off those genes required to make legs, essentially removing those legs from what would be the abdomen in insects."
In addition to shedding light on how major shifts in body design evolved, the new finding could help scientists better understand certain human diseases and deformities. "If you compare [Hbx] to many other related genes, you can see that they share certain regions in their sequences, which suggests that their function might be regulated like this gene," remarks lead study author Matthew Ronshaugen. "This may establish how, not only this gene, but relatives of this gene in many, many different organisms actually work." A number of these genes are involved in cancer and developmental abnormalities, he says, and "they may explain how some of these conditions came to be." ÑKate Wong
RELATED LINK:
"How Limbs Develop," by Robert D. Riddle and Clifford J. Tabin (Scientific American, February 1999), is available for purchase at the Scientific American Archive.
 Image: Matthew Ronshaugen/UCSD |
To be fair, this article doesn't claim that, only a hint.
Where I have a problem is the presumption of some that we have any real clue as to what might cause or drive macroevolution. It's there, I think, that we all need to concede that where the scientific evidence is concerned, "we really don't know" what causes speciation.
WRONG! The fossil record contains many fully formed animals and not one proven transitional one.
God hating “scientists”, the high priests of the secular religion, must insist that these are evolutionary changes. There is no evidence of evolution in the fossil record. But they keep repeating the same mantra. All together now ..."600 billion years ...yada yada yada ..."
How long is this supposed to take?
While that's generally true, without getting into the particulars here, there are some problems with the mating/not mating definition of species. There are still some fuzzy areas around our definitions.
Archaeopteryx.
yada yada yada
In a case of California chipmunks, not more than a few generations. The different species can mate, but do not because the different groups have new matting rituals that the other species does not reognize. Speciation is really a definition of reproductive isolation in the wild.
Where does this come from?
I couldn't find any info in the mechanism at the genetic level for why Thalidomide children happened.
Repoductive isolation could be any number of things as I already said, anything from sexual organs are not compatible, to chromosome number not compatible, to a river or mountain that separates the two communities. This usually results in the two species being genetically different because of breeding only within the immediate group.
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