On another blog, a skeptic took issue with a small segment of my essay, The Rational Essence of Proteins and DNA. It is worth responding to because it will help people see how the new views of evolution support front-loading.
I originally wrote:
Now I have previously argued that the blind watchmaker, like all designers, is limited by the building material that is available. So we need only ask ourselves a simple question – what if we cut down on the diversity of this palette? What if the blind watchmaker only had one member from each color-coded group to work with? What if the blind watchmaker had only the amino acids found in any particular color-coding (only hydrophobics or uncharged hydrophilics, for example)? What of the blind watchmaker only had three amino acids to work with? Say arginine, valine, and glycine? Or leucine, proline, and aspartate? Etc.
Could the blind watchmaker still produce a biosphere as diverse and resilient as that which exists with such scaled down palettes? I doubt this very much.
Since we can think of natural selection and variability as a designer-mimic, and designers are limited by the material they design with and through, we can extend the analogy to ponder in what ways evolution is an expression of its design material, helping us to get closer to the intrinsic factors that drive evolution.
The skeptic replies as follows:
A variety of amino acids occur naturally. With only a single amino acid, we might have a more efficient molecular replicator. From there, other amino acids or derivatives could provide additional capabilities. Amino acids form families, and evidence is consistent with an historical process of amino acids being over time to the genetic code.
Note the skeptic never answered whether the blind watchmaker could produce a biosphere as diverse and resilient as that which exists with such scaled down palettes, but judging from this reply, his answer appears to be ‘no.’ For what the skeptic is proposing is that the blind watchmaker was able to produce a biosphere as diverse and resilient as that which exists because it first expanded its palette. Before getting to that, however, consider the scenario at face value. For even if it is true, the Rabbit has not been erased.
According to this scenario, the blind watchmaker, which is hyper-myopic to the point that is it blind, would be selecting amino acids from a much larger pool that only service the needs to the ‘molecular replicator.’ Fine. Yet built into this selection for such humble needs would turn out to be an explosive front-loading of pre-adaptive potential. That is, the very amino acids selected to meet the modest needs of a molecular replicator in some primitive, quasi-cellular context would “just happen” to constitute a palette more than sufficient to fulfill an immense variety of sophisticated needs far removed from the world of a replicating molecule in a soup – the world of the amazing proteins.
The skeptic then quotes me, “Could the blind watchmaker still produce a biosphere as diverse and resilient as that which exists with such scaled down palettes? I doubt this very much.”
The actual answer is that evolution provides the palette by a process of diversification and adaptation of existing structures.
Studies of the evolution of development characterize the way in which gene regulatory dynamics during ontogeny constructs and channels phenotypic variation. These studies have identified a number of evolutionary regularities: (1) phenotypes occupy only a small subspace of possible phenotypes, (2) the influence of mutation is not uniform and is often canalized, and (3) a great deal of morphological variation evolved early in the history of multicellular life. An important implication of these studies is that diversity is largely the outcome of the evolution of gene regulation rather than the emergence of new, structural genes.
Diversity is largely the outcome of the evolution of gene regulation rather than the emergence of new, structural genes. Another way of saying this is that diversity is largely the outcome of mixing paint and using new styles rather than the emergence of new paint. For the most part, evolution has not provided the palette by a process of diversification and adaptation; evolution as a process of diversification and adaptation has been a function of the palette.
Once you appreciate the subtle shift involved here, it becomes clearer why deep homology supports front-loading.
Deep homology is not entailed by a view where evolution provides the palette by a process of diversification and adaptation. If evolution provides its own palette, then ancient designs based on ancient palettes adapted to another era are supplanted by new palettes and the new and improved designs they provide. It’s this old view of evolution that led the great evolutionary theorist, Ernst Mayr, to predict:
Much that has been learned about gene physiology makes it evident that the search for homologous genes is quite futile except in very close relatives. If there is only one efficient solution for a certain functional demand, very different gene complexes will come up with the same solution, no matter how different the pathway by which it is achieved. The saying “May roads lead to Rome” is as true in evolution as in daily affairs.
And we now know Mayr was wrong, which is encouraging, because if Mayr turned out to be right, front-loading would be a much weaker hypothesis.
In contrast, when evolution is viewed as a process of diversification and adaptation that has been a function of the palette, deep homology is entailed, as deep homology is an expression of this palette of amino acids and thus becomes an emergent palette known as the tool kit.