Tuesday, May 29, 2012

When there is no good news for ID, quote an old book

It is a slow news day over at UncommonDescent. Actually, every day is a slow news day there, since there are no ID scientists doing ID research publishable in peer reviewed journals. So the UD news desk, Denyse O'Leary, dips into the pages of John Sanford's Genetic Entropy for an extended quote.

During the last century, there was a great deal of effort invested in trying to use mutation to generate useful variation. This was especially true in my own area – plant breeding. When it was discovered that certain forms of radiation and certain chemicals were powerful mutagenic agents, millions and million of plants were mutagenized and screened for possible improvements. Assuming the Primary Axiom (that the secies are merely the product of random mutations plus natural selection), it would seem obvious that this would result in rapid "evolution" of our crops. For several decades this was the main thrust of crop improvement research. Vast numbers of mutants were produced and screened, collectively representing many billions of mutation events. A huge number of small, sterile, sick, deformed, aberrant plants were produced. However, from all this effort, essentially no meaningful crop improvement resulted. The entire effort was a failure, and was eventually abandoned. – Genetic Entropy & the Mystery of the Genome , page 25

It is an interesting quote, and I'd like to address the ideas in it by referencing the development of high-yielding varieties of wheat and rice during the Green Revolution, work which took place during the same approximate time as Sanford refers to.

First, let us note that Sanford is going to trade upon the ambiguity in his phrase "random mutations plus natural selection". RM+NS, as it is often abbreviated in internet dialogs, can mean either any kind of genomic variation and any kind of selective pressure, or only the substitution of exactly one nucleotide for another in DNA and the survival of the fittest. When making a claim against "Darwinism" or "evolutionism" opponents imply the first, broad meaning. When asked to defend a claim, they retreat to the narrow meaning.

No modern scientist thinks nucleotide substitution alone built the genomes of every species alive, and those extinct. Reading the genomes of many species has shown how  groups of genes have been duplicated as groups, sometimes across species boundaries. Importantly for the case of useful plants, the entire genome of plants such as wheat and potatos has been duplicated more than once. Each cell of a wheat plant has six complete copies of its genome! These large scale restructurings are responsible for the rapid change in plant and animal evolution, compared to bacterial evolution.

Second, if we look at the Green Revolution - the rapid expansion of crop productivity around the world since World War II - we see that the main driver was new kinds of wheat and rice. These new cultivars grew shorter stems, which were mechanically stronger than previous wild-type long stems. The strength of the stem was important when the seed head grew bigger. Without a strong stem, the plant fell over (lodged).

The short stems are the result of point mutations in the genome. We've known this for a long time. We know that the mutations affect the growth signal processes, stunting growth compared to the wild-type plant. So Sanford is flat wrong to suggest that we have never found beneficial mutations in plants. He has a fig leaf to hide behind in that these mutations were found in naturally growing variants of wheat and rice. They were not induced by human radiation or chemical experiments.

Since we now know the size of the wheat genome, we could calculate the expected time until discovery of a beneficial mutation, using the techniques of radiation and chemical mutagenesis. I'm going to guess it would be on the order of millions of years, if each batch of seeds has to be grown and tested for increased function.

This is an essential contrast between the small bodied, asexual evolution of bacteria and the large bodied, sexual evolution of plants and animals. We do see rapid response to chemical stresses, such as anti-biotic resistance, in bacteria because the population being stressed is trillions of individuals. We can't test a population of trillions of plants or animals. Perhaps Sanford hasn't thought about the implications of that, or perhaps he has and would prefer to obfuscate them.

The idea that exposing pollen grains to radiation would advance the species is 'hopeful monster' thinking. That said, it worked! Dwarf wheat and rice have fed billions of people. Sanford's pessimism is misplaced.

2 comments:

Anonymous said...

Now, is this the same Sanford that seems to think that evolution requires genes to be 'built' one mutation at a time?

David vun Kannon said...

One and the same.