12 February 2007
Prof Questions Darwinian Dogma
by Kate Melville
In a new paper that challenges the Darwinian model of evolution, University of Pittsburgh professor, Jeffrey H. Schwartz, contends that evolutionary changes occur suddenly as opposed to the Darwinian model of evolution, which is characterized by gradual and constant change. Schwartz's paper, "Do Molecular Clocks Run at All? A Critique of Molecular Systematics," appears in the latest issue of the journal Biological Theory.
What Schwartz dubs "Molecular Assumption" (MA) entered evolutionary lore when, in 1962, biochemists Emil Zuckerkandl and Linus Pauling demonstrated species similarity through utilizing immunological activity between the blood's serum and a constructed antiserum. Upon observing the intensity of the serum and antiserum reactivity between human, gorilla, horse, chicken, and fish blood, they deduced "special relatedness" - that is, the more intense the reaction, the more closely related the species were supposed to be.
Because fish blood was most dissimilar, it was assumed that the fish line diverged long before the other species. Human and gorilla blood were the most similar, meaning both species had the least amount of time to diverge. Ultimately, the Darwinian model of constant evolutionary change was imposed upon the static observation made by Zuckerkandl and Pauling.
Since then, the scientific community has accepted the MA as a scientific truth, but Schwartz has a different view. "That always struck me as being a very odd thing - that this model of constant change was never challenged." Schwartz has his own theories regarding evolution, which are backed by recent developments in molecular biology and prominent gaps in the fossil record.
Schwartz's argument centers on how the structure of the genome does not keep changing based on the presence of stress proteins, also known as heat shock proteins. These proteins are located in each cell, and their main function is to eliminate the potential for cellular error and change via maintaining normal cellular form through protein folding.
This regular cellular maintenance is what Schwartz points to in 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 our molecules were constantly changing, it would threaten proper survival, and strange animals would be constantly emerging 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. 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 myriad years prior.
Schwartz is intrigued by the failure of the scientific community to question an idea that is more than 40 years old: "We cannot prove a whole lot in evolutionary biology, and our findings will always be hypothesis. There is one true evolutionary history of life, and whether we will actually ever know it is not likely. Most importantly, we have to think about questioning underlying assumptions, whether we are dealing with molecules or anything else," he said in conclusion.
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Source: University of Pittsburgh