Some Reflections on Stent's Lecture
As noted in my previous post, there was a lecture at UNLV tonight entitled "Intelligent Design: A Unique View of Globalization and Science" by Dr. Gunther Stent. Here are my reflections on the lecture.
The lecture hall was packed--standing room only. Dr. Stent is a recognized expert in molecular genetics, having written an important textbook on the subject. He seemed quite amiable, though because of his age--he's probably in his 70s or 80s--he was hard to hear.
Anyway, I was rather disappointed in the lecture because it hardly engaged with intelligent design at all. Dr. Stent did describe ID as "bizarre", but no explanation or justification was given for that claim. A couple times he lumped it in the same category as "creationism", evincing no clear awareness that the two movements, while overlapping in some respects, are quite distinct.
Most of the talk wandered over a wide array of issues, from comparing C.H. Waddington's and Herbert Spencer's views on the grounding of moral values in Darwinian theory to an extended discussion of Kimura's theory of 'neutral evolution' to speculations on cultural evolution and the possible role that differences in the ratio of brain size to body size might have on rates of "organismal" (or phenotypic as opposed to "genetic" or genotypic) evolution.
His central concern seemed not to be ID at all but contrasting Kimura's neutral evolution with neo-Darwinian natural selectionist orthodoxy. This part of the talk was quite interesting. The basic idea behind neutral evolution is that most of the genetic variation that occurs in a population has little or no direct relation to the "fitness" of an organism. Accordingly, such changes are invisible to natural selection. Nevertheless, if these "neutral" changes proliferate sufficiently throughout a population then they may become "fixed" in the gene pool. Hence, genetic change can occur in species over time even though that change has not been selected for.
According to Dr. Stent, the rate of evolution due to neutral evolution is a factor of (1) the rate of occurrance of a given neutral mutation, and (2) its rate of fixation in a population's gene pool. A given mutation is more likely to occur in a larger population, but fixation is more likely to occur in a smaller population, so (1) and (2) tend to balance each other out. What this means, according to Dr. Stent, is that the rate of neutral evolution is relatively invariant across factors like size of population, rate of reproduction, life-span, and so forth. Instead, the rate of neutral evolution is a more-or-less linear function of time because the other factors balance each other out. Hence, there is a relatively constant "evolutionary-molecular clock".
Dr. Stent seems to think that neutral evolution is the primary source of changes in a population's gene frequencies over time, with natural selection playing only an occassionaly and largely conservation role by weeding out the most unfit. He did suggest that neutral evolution might pose a challenge for ID because random point mutations and genetic drift seem to point away from any sort of telic directedness.
One question I have about this is that if most genetic changes are really selectively neutral, and most of evolution consists in such neutral changes, then it seems to me that it's going to be somewhat hard to account for the occassional rapidity of phenotypic evolution, as in the Cambrian explosion. The problem is that neutral genetic changes have no positive tendency to distribute themselves throughout a population because they are invisible to selection pressure. So in any halfway decent-sized population it could take hundreds or thousands of generations for even one neutral point mutation to become fixed in the gene pool. Given that some creatures have relatively low birth rates, if most of evolution occurs this way, then I'm rather skeptical that there's been anywhere close to enough time for the whole Darwinian tree of life to emerge.
One final remark: Early on in his talk, Dr. Stent admitted quite frankly that the origin or life is utterly "mysterious". He said that no credible naturalistic theory exists to explain how life emerged from non-life. He even went so far as to say that the very quest for a plausible naturalistic origin of life scenario "seems hopeless" and that researchers in that field were quite "discouraged". Later in the talk he referred to Francis Crick's notorious idea of "directed panspermia", basically the notion that life of Earth was engineered by extraterrestrial aliens and then seeded on the Earth. Dr. Stent obviously regarded Crick's suggestion as silly, but by his own admission neither he nor origin-of-life researchers have anything much better to offer. It seems to me that this admission on his part shows that whatever the merits of his views on neutral evolution, ID is still in the game. The most obvious cases of intelligent design are those that stubbornly resist reductive explanation in terms of natural law, chance, or some combination thereof. The origin of life is increasingly looking like just a case.