Thursday, October 05, 2006

An Inquisitive Student

A biology student named Amanda recently posted a message within a Yahoo group asking some intelligent questions. Her post follows. My comments are in bold print.

"Are there any professional geneticists, embryologists, Morphologists, etc. in the forum? If so, maybe you can help me. I'm a Junior studying biology, seeking to go on to graduate school and go into either genetics or some type of cell or molecular research. I love this type of biology, I love organic chemistry, biochemistry, and research in general, and I also love the Word of God, and am a Christian. I completely comprehend the idea of Natural Selection as proposed by Darwin and find it to be completely logical and reasonable, but I cannot reconcile it with my knowledge of genetics, how the cell works, how genes are expressed, and so on.

I feel that Natural Selection makes sense when discussed simply in terms of an
entire organism, but I've never seen it tied with the way DNA actually works (even though I am continuously told that NS takes place genotypically, not phenotypically, otherwise LaMarch would have been right)."

Natural selection was a logical construct when first introduced and is still a concept that, for the most part, is unsupported by direct evidence. An article by David Berlinski entitled 'The Strength of Natural Selection in the Wild' is one of very few that refer to actual studies related to natural selection.

In order for NS to even start, there would have had to be an unimaginable number of random genetic mutations, and I think that is defended usually with the idea of an incredibly old earth-I guess people can accept that there is a chance that many mutations could take place over billions of years, and there's probably some type of equation for that (although personally i think the age of the earth has repeatedly been determined though circular reasoning.) But I simply can't accept that an enormous series of random mutations brought about the exact sequences of nucleotides necessary for the complex functions that even the simpliest cell must carry out in
order to survive.

Your skepticism is not without reason. Here is an interesting reference to work done by Dr. Ralph Seelke.

"Tryptophan Synthase A, a protein which enables E. coli to synthesize tryptophan, an amino acid necessary for life, is the target for this study. He was able to locate the trpA gene and “knock out” 1, 2, 3 or 4 sites which prevents this protein from being made. The E. coli were placed in a tryptophan poor environment in which they could live, but not do well. In so doing, Seelke replicated an environmental stress such as those theorized by Darwinians which drive evolution. If mutations occurred which enabled some bacteria to sythesize tryptophan, this would convey a selective advantage, and those bacteria would dominate.

The Results: Those E. coli who only had one site to overcome essentially evolved overnight. This one error was corrected and the adapted E. coli dominated. HOWEVER, if two independent events (two mutations) are needed, it appears nothing happens. After 1,000’s of generations, not one bacteria has overcome the barrier presented by the requirement of just 2 independent mutations. It appears, at this time, evolution cannot even produce two independent events needed to become fitter. This makes the idea that the 40 or so proteins required for the bacterial flagellum to all be produced in the right place at the right time sound downright ludicrous."

"This includes coding for the transciption factors necessary to even transcribe the DNA itself and manufacture proteins. Which is strange because Transcription factors are proteins-so how were the first proteins made? It takes a large number of complex reactions and comfirmational changes for a cell to make a protein, it's hardly a spontaneous reaction. There are so many intricate systems in life that would not work should one tiny thing change. I can't wrap my brain around how random genetic mutations could result in the amazingly complex, yet smallest unit of life-the cell."

Amanda has put her finger on the Achilles heel of Darwinism namely, the inability to formulate a coherent theory of descent from a prebiotic starting point. As indicated the synthesis of proteins not only requires a great deal of nucleotide specificity, it also entails proteins that bind to promotor regions, an enzyme- RNA polymerase- required to transcribe genes, a complex of tRNAs and tRNA aminoacyl synthetases required to correctly match codons with 20 different amino acids, ribosomes involved in peptide elongation and more. Amazingly the proteins needed to enable protein synthesis are themselves coded for by the same DNA whose transcription and translation they make possible.

"I find it especially difficult to comprehend since the frequency of mutations seen today is so small, and most mutations are harmful-the cell even has defenses against mutations, and mechanisms to check and correct them."

Another good point. Genomes come equiped with mechanisms designed to detect and correct errors leading to mutations and damage to DNA caused by environmental factors like ultraviolet light and chemical reactions. This blog has recently featured a series of posts on just this issue. The pervasiveness of DNA repair mechanisms among biological organisms leads to the question of how cellular life would have been possible without them at any point in time.

"Maybe I haven't completely grasped the whole evolutionary theory yet, maybe I'm missing something-but I feel like I'm stepping into a different world when I leave my genetics/development class and step into my vertabrate diversity class. There are theories of origen, and explanations for what we see phenotypically today, but nothing in between. Is there anyone who can provide some explanation?"

Amanda, I think you have a good grasp of evolutionary theory. In fact your grasp of it is better than that of most defenders of the theory. Your independent thinking is to be admired. I hope your intentions of a graduate degree in a biological field of study are realized. We could use some good young thinkers.


At 9:56 AM, Anonymous Mike Godfrey said...

excellent post William,well done Amanda.
This reminds me of Dr Behe's Hedgehogs trying to get across a multilane highway (motorway for us English).
To all intents and purposes an impossible task.Darwinian Evolutionist are always talking about small steps-but the steps are not dictated by evolutionists but by the environment Survival may mean big steps.

At 11:47 AM, Blogger William Bradford said...

Anonymous- I'd publish your comment were it not for your childish name calling. It's a good reason to prefer anonymity. As to your comment about natural selection, there are many references on the topic but few actually cite studies of organisms in their natural habitat or in the sample sizes and time periods applicable to the Kingsolver study. The following is quoted from that study:

"How strong is phenotypic selection on quantitative traits in the wild? We reviewed the literature from 1984 through 1997 for studies that estimated the strength of linear and quadratic selection in terms of standardized selection gradients or differentials on natural variation in quantitative traits for field populations. We tabulated 63 published studies of 62 species that reported over 2,500 estimates of linear or quadratic selection. More than 80% of the estimates were for morphological traits; there is very little data for behavioral or physiological traits. Most published selection studies were unreplicated and had sample sizes below 135 individuals, resulting in low statistical power to detect selection of the magnitude typically reported for natural populations."

There are a plethora of books papers dealing with theoretical musings and others dealing with the microsopic world. Relatively few focus on larger organisms. Control factors are difficult in natural habitats.

As to your criticism of spelling I cut and pasted the post as is. When quoting it is not necessary or even advisable to insert spelling or grammatical corrections.

At 11:58 AM, Blogger William Bradford said...

Mike: "Darwinian Evolutionist are always talking about small steps-but the steps are not dictated by evolutionists but by the environment Survival may mean big steps."

That's why logic alone is insufficient to confer credibility to a hypothesis. Another possible difficulty to selection is the problem of intermediate steps lacking selective value. Each incremental step must confer a significant advantage. If the advantage accrues to a single individual then that individual's descendents must outproduce the remainder of the population for the trait to become predominant.

At 6:21 PM, Blogger Amanda said...

I really appreciate you taking the time to commennt on my post and give me some advice and resources. Someone sent me the link to your blog, and I think it's great what you are doing here. I received very few meaningful responses from the yahoo site and my post caused an ongoing argument between two people. Yikes. I think it's hard for people to remain coolheaded about these topics. Thank you for presenting interesting facts and educated discussion without the bickering. :)

At 7:56 PM, Blogger William Bradford said...

Thanks for the comment Amanda. It is difficult for many to retain a cool head when discussing these topics. If there are readers aware of other research studies analogous to 'The Strength of Phenotypic Selection in Natural Populations' then kindly advise and identify them.


Post a Comment

Links to this post:

Create a Link

<< Home