Deflating Dobzhansky’s Grand Assumption, Revisited: Is the Assumption Still Necessary?


Theodosius Dobzhansky on Equating Microevolution and MacroevolutionRecently, a fellow Appalachian objected to my use of a 1937 quote from Theodosius Dobzhansky based on an implied appeal to novelty. An appeal to novelty is the fallacious assumption that just because something is newer, it must be better or more true than something older. He basically asked, given my 1937 quotation, whether I would also use 1937 medical science and then accused me of supposing that science “never changes, never gathers evidences, never formalizes a hypothesis into a theory” because I did not use a more recent quote. I know, I know… it’s a bad argument, but let’s make this an educational experience.

First, to demonstrate how silly his rhetoric is, let’s answer the question of whether I would use 1937 medical science? Well, it depends upon the science. Consider, for example, medical hygeine. History records that in the late 1840’s, Dr. Ignaz Semmelweis, then working as an assistant in the maternity wards of a Vienna hospital, observed that the mortality rate in a delivery room staffed by medical students was up to 3 times greater than that of a second delivery room staffed by midwives. He further observed that these medical students were coming to the delivery room straight from working on cadavers, so he figured these guys must be carrying infection from their autopsies to birthing mothers. Accordingly, he ordered doctors and medical students to wash their hands with a chlorinated solution before examining women in labor, and the death rate in his maternity wards eventually dropped to less than one percent.

Amazingly enough, I still insist that doctors practice 1840s medical science when it comes to pre-exam handwashing precisely because it works. Medical science has marched onward, but some things remain true despite the passage of time. If it ain’t broke, don’t fix it.

Which brings us to our 1937 Dobzhansky quote, from Genetics and the Origin of Species:

“There is no way toward an understanding of the mechanism of macroevolutionary changes, which require time on a geological scale, other than through a full comprehension of the microevolutionary processes observable within the human lifetime. For this reason we are compelled at the present level of knowledge reluctantly to put a sign of equality between the mechanisms of micro– and macroevolution, and proceeding on this assumption, to push our investigations as far ahead as this working hypothesis will permit.” [emphasis mine]

In an article entitled Deflating Dobzhansky’s Grand Assumption, I noted:

“Dobzhansky had to make an assumption that small changes could account for big changes. Why? Because he couldn’t observe them. Because such changes allegedly took place over long periods of time that were, well, prohibitive to say the least. So he had to make an assumption.”

I went on in that article to demonstrate why this was essentially impossible, since the horizontal changes observed do not add genetic information as would be required of the microbes-to-man evolution model, but rather are more consistent with the creationist position of variation within created kinds.

But the question here is whether Dobzhansky’s quote has been made erroneous given modern science. In other words, since science does advance, since it does change, since it does gather evidence, is there any more need for Dobzhansky’s Grand Assumption. Have we essentially proven that small, observable horizontal biological changes [i.e., adaptation, speciation, mutation, natural selection] eventually lead to proposed vertical [phyletic] microbes-toman evolutionary change? And the answer is a resounding NO, precisely because the major problem Dobzhansky highlights is still in place: there is no way to observe the proposed vertical changes, common refered to as macroevolution. The assumption is still necessary.

Stephen Jay Gould said the following in 1977 article [re-published under a different title in 1980]:

“The extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology. The evolutionary trees that adorn our textbooks have data only at the tips and nodes of their branches; the rest is inference, however reasonable, not the evidence of fossils. [“Evolution’s Erratic Pace” in Natural History86(5):12-16. 1977. Also published as “The Episodic Nature of Evolutionary Change” in The Panda’s Thumb, pp. 179-185. New York: W. W. Norton & Company. 1980.]

Note that, while an advocate of microbes-to-man evolution, he admits that the theory’s larger claims consist of inference. Inference is defined as “the process of deriving the strict logical consequences of assumed premises; the process of arriving at some conclusion that, though it is not logically derivable from the assumed premises, possesses some degree of probability relative to the premises; or, a proposition reached by a process of inference.” While inference involved evidence and reason, it requires an assumed premise, or to put it more bluntly: an assumption. The reason inference is necessary is because, as Dobzhansky noted back in 1937, the time scale involved for proposed macro-evolutionary changes makes direct observation impossible [barring the invention of a time machine anyway].

This is exactly why creationists have long pointed out that there is a difference between operational science, which is directly testable, observable, repeatable and falsifiable, and origins science, which deals with the unrepeatable, unobservable past.

As recently as 1990, Tim Berra admitted much the same in his book Evolution and the Myth of Creationism. Answering the objection that Biologists have never seen a species evolve, he says:

“On a small scale, we certainly have… Major evolutionary changes, however, usually involve time periods vastly greater than man’s written record; we cannot watch such changes, but we can deduce them by inference from living and fossil organisms.” [Stanford University Press, pp. 129-130]

While his comments answer a creationist straw man [Tim, we affirm speciation, an observable horizontal biological change; i.e., the created kind is not analogous to the species taxon but is found, generally speaking, more at the family taxon], he admits that inference is necessary, so the assumptive element remains.

And Richard Dawkins has admitted this even more recently in a 2004 interview with Bill Moyers:

“Evolution has been observed. It’s just that it has not been observed while it’s happening.”

What did he mean by this curious statement? When Moyers pressed him about it, he and Dawkins had the following exchange:

DAWKINS: “The consequences of. It is rather like a detective coming on a murder after the scene. And you… the detective hasn’t actually seen the murder take place, of course. But what you do see is a massive clue. Now, any detective…

MOYERS:Circumstantial evidence.

DAWKINS: Circumstantial evidence, but masses of circumstantial evidence. Huge quantities of circumstantial evidence. It might as well be spelled out in words of English. Evolution is” true. I mean it’s as circumstantial as that, but it’s as true as that.”

They claim they’ve gathered a lot of circumstantial evidence, yet creationists interpret this same evidence to support the veracity of the Scripture’s account of history. The bottom line is that Dobzhansky’s Grand Assumption is still very much in force despite the antiquity of the quote, and that the same sentiment is being expressed even today, precisely because there is no means by which to directly observe proposed microbes-to-man macro-evolution in action because this process is believed to take place over long ages.

-Rev Tony Breeden

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