We’re back. Inspector Bunny, you said that the SRP was an elegant system that would go on to influence evolution. Can you expand on that?
Sure. A key component of the SRP is one of the domains that is part of the RNA component, known as the Alu domain. This Alu domain is not needed for life to exist, given the fact that most bacterial SRPs don’t have it. But some do have it. And interestingly enough, those bacterial versions of the SRP look more like the human Alu domain than other protozoan domains. In other words, in some bacteria, the SRP is needlessly complex for survival, but appears to be needed for the subsequent evolution of more complex states.
Well, first of all, bacterial don’t need the Alu domain because they don’t need to pause ribosomal synthesis. The cells are so small that they can hook up the ribosome to the membrane protein channel while the gene is in the very process of being expressed. But in the much larger eukaryotic cell, whose cytoplasm is cut off from the DNA by the nuclear membrane, the pause function is needed. And it is the Alu domain that serves as the core component for delivering this pause function. In other words, some bacteria contain an SRP that would function as one preadaptation that would nudge evolution toward the emergence of the eukaryotic cell, a cell plan that would be needed to evolve a complex animal state.
Oh, so you are saying the Alu domain that is part of the RNA component of the SRP is there to facilitate evolution?
Sure. I’m saying we can perceive things like this and there is nothing to say we would be wrong. From there, we would find example after example of other preadaptations, all converging on the same nudge.
Oh, that is a whole set of other features found in various bacteria. We’ll get to some of those eventually, but let’s instead notice that the SRP is apparently not finished in guiding subsequent evolution.
So you are saying there is more to the SRP story than being an elegant system that not only solves a core problem for life, but also facilitates the evolution of the complex eukaryotic state?
Well done, One with Glasses. Billions of years after the origin of eukaryotes, fast-forward to the evolutionary emergence of primates. If primates had not evolved, humans could not have evolved. Something very interesting happened very early in primate evolution. The sequence for the Alu domain was copied and duplicated and gave birth to a new retrotransposon – the Alu element.
Think of a retrotransposon as a device that can make copies of itself and spread throughout the entire genome. If you are a duck, you’ll see it as some selfish parasite and yawn. But we bunnies, while understanding how the ducks see it, also see a deeper meaning – it is a mechanism to reformat entire genomes. That is, it is a mechanism to enhance and facilitate evolution. Remember, the blind watchmaker is completely at the mercy of the variability that life hands it. These Alu elements set about reshaping the genome, offering the blind watchmaker a vastly larger array of options to edit. And during primate evolution, these Alu elements were busy trying out different reformatting solutions for brain development.
So the SRP then ultimately played a role in the evolution of the human brain?
Yeah, a big role. In fact, without the Alu elements, he have no reason to think the human brain would have evolved. What’s more, without retrotransposons, we have no reason to think the human brain could have evolved.
Earlier, I mentioned that all designers are constrained by the available design material. Since the blind watchmaker is a designer-mimic, and its design material is largely protein, then we need to ask just what could the blind watchmaker actually make without proteins? Would it still be able to produce a world like the one that exists?
Well, here we see the same theme, but in this case, it is not design material, it is design strategies that are available. The Alu elements allow for the possibility of massive and relatively speedy reformatting and adaptation. Could the blind watchmaker have sculpted something like a human brain without this mechanism being available?
I see. So you are saying that the blind watchmaker will always do what the blind watchmaker does – cull available variability according to some fitness test. But that because of the SRP, the blind watchmaker has more options to work with.
Sure. What’s more, some of those options will always sit there in-waiting, knowing that sooner or later the blind watchmaker is bound to call upon them. It’s just a matter of time. And once called on, they can help steer and guide the blind watchmaker, causing something remarkable to emerge on the stage that in turn will add further guidance when it comes to future available options.
Y’see, this Alu story gets even more interesting.
Well, I’ve run out of time and need to return to all that inspecting right away.
Okay, Inspector Bunny. Thanks for talking with us. We’ll be sure to follow your next hare-brained installment.
This is all so dessspicable!