ID Foundations 15(c) — A FAQ on Front-Loading, thanks to Genomicus
|February 1, 2012||Posted by kairosfocus under Origin Of Life, Genetics, ID Foundations, Cell biology|
Onlookers, Geno concludes for the moment with FAQ’s:
A Testable ID Hypothesis: Front-loading, part C
In the last two articles on front-loading, I explained what the front-loading hypothesis is all about and some research questions we can ask from a front-loading perspective. This article will be an FAQ about the front-loading hypothesis. So, without further introduction, let’s begin (note: some of the content of this FAQ can be found in the previous two articles).
- What is front-loading?
“Front-loading is the investment of a significant amount of information at the initial stage of evolution (the first life forms) whereby this information shapes and constrains subsequent evolution through its dissipation. This is not to say that every aspect of evolution is pre-programmed and determined. It merely means that life was built to evolve with tendencies as a consequence of carefully chosen initial states in combination with the way evolution works.” Mike Gene, The Design Matrix: A Consilience of Clues, page 147
In short, this ID hypothesis proposes that the earth was, at some point in its history, seeded with unicellular organisms that had the necessary genomic information to shape future evolution. Necessarily, this genomic information was designed into their genomes.
- How is front-loading different from directed panspermia?
In a paper published in the journal Icarus, Francis Crick and Leslie Orgel proposed the hypothesis of directed panspermia. According to this hypothesis, the earth was intentionally seeded with life forms by some intelligence. The front-loading hypothesis goes a step further and proposes that these life forms contained the necessary genomic information to shape the course of future evolution. For example, the origin of metazoan complexity would have been planned and anticipated by the genomic information in the first genomes. Thus, the front-loading hypothesis is inherently teleological and an ID hypothesis.
- Does front-loading propose that all the genes found in life were in the first life forms?
No, it does not. Front-loading does not suggest that all genes were there from the start. Indeed, many genes found in modern life forms are probably the result of purely unplanned mechanisms (gene duplication and subsequent divergence, for example). Nevertheless, genes essential for the origin and development of the metazoan body plan would be present in the first genomes (or have homologs in the first genomes).
- If genes necessary for the origin of metazoan life forms were placed, then random mutation would have destroyed them and they would decay, right?
This is a common objection to the front-loading hypothesis, but it can be easily answered. These genes would be given an important function in the first life forms, such that they would be preserved across deep time. Front-loading doesn’t involve much of simply turning genes (that were previously unexpressed) on at some given time.
- How could sophisticated molecular systems be front-loaded?
There are two basic solutions to the problem of front-loading sophisticated molecular systems, but more research is needed so that we can find out exactly how these solutions would work in practice. In theory, however, there’s the “bottom up” approach and the “top down” approach to front-loading molecular systems. In the “bottom up” approach, the original cells would contain the components of the molecular machine we want to front-load, but these components would be carrying out functions not related to the function of the molecular machine. Then, somehow (here’s where we need research), something causes them to associate such that they fit nicely with each other, forming a novel molecular machine.
The “top down” approach proposes that the first cells had a highly complex molecular machine, composed of, say, components A, B, C, D, E, F, G, H, and J. If we want to front-load a molecular machine composed of components A, B, C, and D, then this highly complex molecular machine contains a functional subset of A, B, C, and D. In other words, components E, F, G, H, and J would simply have to be deleted from the highly complex molecular machine, resulting in a molecular machine composed of A, B, C, and D. This model is actually testable. Under this model, we would tentatively predict that a homologous system of a molecular machine will be more complex if it is more ancient than the molecular machine.
- What testable predictions does the front-loading hypothesis make?
There are several testable predictions the front-loading hypothesis makes:
- Cytosine deamination. Of the three bases in DNA (adenine, guanine, and cytosine) that are prone to deamination, cytosine is the most likely to undergo deamination. This ultimately results in a C –> T transition. Cytosine deamination often causes severe genetic diseases in humans, so why would a front-loader choose cytosine as a base in DNA? It has been observed that C –> T transitions result in a pool of strongly hydrophobic amino acids, which leads to the following prediction from a front-loading perspective: a designer would have chosen cytosine because it would facilitate front-loading in that mutations could be channeled in the direction of increased hydrophobicity. This prediction would be confirmed if key protein sequences in metazoan life forms were the result of numerous C –> T transitions.
- The genetic code. The front-loading hypothesis proposes that the universal optimal genetic code was present at the dawn of life: in other words, we won’t find precursors of sub-optimal genetic codes, because the genetic code was optimal from the start. Further, the front-loading hypothesis predicts that all 20 amino acids would have been used in the first life forms, and that the transcription, translation, and proof-reading machinery would have all been present at the start of life on earth.
- Biological complexity. Front-loading predicts that the last universal common ancestor (LUCA) was quite complex, complete with genes necessary for the origin and development of metazoan life forms.
- Protein sequence conservation. In eukaryotes, there are certain proteins that are extremely important. For example, tubulin is an important component of cilia; actin plays a major role in the cytoskeleton and is also found in sarcomeres (along with myosin), a major structure in muscle cells; and the list could go on. How could such proteins be front-loaded? Of course, with some of these proteins they could be designed into the initial life forms, but some of them are specific to eukaryotes, and for a reason: they don’t function that well in a prokaryotic context. For these proteins, how would a designer front-load them? Let’s say X is the protein we want to front-load. How do we go about doing this? Well, firstly, we can design a protein, Y, that has a very similar fold to X, the future protein we want to front-load. Thus, a protein with similar properties to X can be designed into the initial life forms. But what is preventing random mutations from basically destroying the sequence identity of Y, over time, such that the original fold/sequence identity of Y is lost? To counter this, Y can also be given a very important function so that its sequence identity will be well conserved. Thus, we can make this prediction from a front-loading perspective: proteins that are very important to eukaryotes, and specific to them, will share deep homology (either structurally or in sequence similarity) with prokaryotic proteins, and importantly, that these prokaryotic proteins will be more conserved in sequence identity than the average prokaryotic protein. Darwinian evolution only predicts the first part of that: it doesn’t predict that part that is in bold text. This is a testable prediction made exclusively by the front-loading hypothesis.
- Does the front-loading hypothesis suggest that evolution was programmed?
No. Front-loading does not propose that all biological innovations were the result of planning and teleology.
The more I discuss front-loading with its opponents and proponents, the more I will add to this FAQ. Please add any questions, comments, etc., below.
Over the years, I have become quite interested in the discussion over biological origins, and I think there is “something solid” behind the idea that teleology has played a role in the history of life on earth. When I’m not doing multiple sequence alignments, I’m thinking about ID and writing articles on the subject, which can be found on my website, The Genome’s Tale.
I am grateful to UD member kairosfocus for providing me with this opportunity to make a guest post on UD. Many thanks to kairosfocus.
Also see The Design Matrix, by Mike Gene. >>
So, here we have one specific model for how ID could possibly have been done. Obviously, not the only possibility, but a significant one worthy of investigations. END