|
scutus -> RE: Nested Hierarchy violations? (3/3/2007 10:08:26 PM)
|
The journal Biological Theory was only launched in 2006 and it's a pretty obscure one, so that's why I've been having trouble finding information on it.
I find Schwartz's article bizarre. I don't get what he means by this:
quote:
Schwartz argues that the structure of the genome — the genetic material that controls an organism’s development — does not keep changing, based on the presence of stress proteins, also known as heat shock proteins, in each cell. Their main function is to eliminate the potential for cellular error and change. This regular cellular maintenance is what Schwartz says is behind his refutation of constant cellular change. “The biology of the cell seems to run contrary to the model people have in their heads,” says Schwartz. He contends that if molecules were changing constantly, it would threaten proper survival, and strange animals would be emerging rapidly all over the world. Consequentially, Schwartz argues that molecular change is brought about only by significant environmental stressors, such as rapid temperature change, severe dietary change or even physical crowding.
If an organism’s stress proteins are unable to cope with a significant change, the genomic structure can be modified. However, Schwartz notes, a mutation also can be recessive in an organism for many generations before it is displayed in its offspring. Whether or not the offspring survives is another matter. Is he suggesting that mutations (molecular change he calls it) only happen in the case of heat? I thought heat shock proteins were only useful in proteins, not genetic materials...
quote:
If it does in fact live, the presence of this genetically modified organism is not the product of gradual molecular change but a sudden display of the genetic mutation, which may have occurred many years prior, he says. Um, I think he's getting mixed up with molecular evolution and the expression of mutations. Gradual molecular evolution happens in the genetic material in germ cells and accordingly through descendants/populations. Individual somatic mutations happen all the time and they can be suddenly expressed into the phenotype...
He makes this conclusion at the end:
quote:
But only altered
germ cells have potential evolutionary impact. In short, the
notion that molecules of germ cells—DNA, RNA, and proteins
and transcription factors necessary, e.g., for DNA repair,
protein folding, chaperone functions, and control of signal
transduction pathways, which are necessary for the survival
of cells and their bearers—are in states of perpetual change is
not, in our present understanding of cell biology, tenable. This
does mean that “molecular change” does not occur; only that
mechanisms provoking such change in germ cells are likely instantaneous
and stochastic and probably often lethal (Maresca
and Schwartz 2006)—which will preclude their persistence
into future generations. Which is again, bizarre. Mutations happen all the time and they are often detrimental or lethal, but Schwartz seems to think that evolution is not gradual, that genetic material is not in a constant flux and that mutationonly happens in short jumps. He's arguing for a speeded up Punctuated Equilibrium. I think he's put up a strawman because Neo-darwinism has accepted PE as an equally likely mechanism alongside the traditional gradual evolution.
What he's challenging is the assumption in molecular phylogeny that more similar creatures are more closely related. But I don't think that's true of today. Now scientists in systematics use cladistical methods. But apparently he doesn't think so: quote:
Although
this will undermine the assumed hegemony of molecular systematics
in determining phylogenetic relationships, it will
mend the unnatural schism that has kept morphological and
molecular systematics apar That was well over thirty years ago. Science has moved on from simplistic notions that just because proteins are more similar between certain animals, they must be closely related. They use molecular data and put it into phylogenies now, with multiple lines of evidence.
|
|
|
|