Deep Homology and Front-loading

When purpose is assigned to natural processes. That is usually where such discussions lead. Perhaps I have jumped the gun on this one . . . time will tell.

The paper I cited describes the structural similarities between ubiquitin and its prokaryotic homologs. Yet it is the basic structure of a protein that determines its function - along with the proteins it interacts with, of course. My point is that loading the first genomes with an ubiquitin-related fold allows it to be easily co-opted into the role used by eukaryotes.

This is true no matter what the origin of ubiquitin is, and is easily accomplished by non-teleological processes.

Understood. Quite right. I personally favor the hypothesis that the LUCA was prokaryotic, and not eukaryotic, although some researchers say that the LUCA was more of a eukaryote precisely because of its complexity and the large number of proteins its genome encoded. This is fully compatible with front-loading. Because the mutations do happen, and over deep time, a protein sequence can change quite extensively - to the point that it is no longer the original protein (but structurally similar, nonetheless, and this is what matters). The universal distribution of ubiquitin among eukaryotes strongly implies that it is necessary for eukaryotic existence, does it not? True, it could be a "frozen accident." But the front-loaders aren't going to gamble their chances on accidents. It would be far better design logic just to put that protein fold into the first cells.

No more than the fact that the water fills the hole implies that the hole was necessary for the water. The only thing implied is that ubiquitin was just good enough to work. But there is evidence of the existence of accidents while no one has ever presented any evidence of the existence of the front-loaders.

Metazoans don't survive that well in an environment like that of the early, hostile earth ya know. Alternatively, you could put some cyanobacteria into the planet's oceans. That's why terra-forming is intimately linked with front-loading. In order to ensure that animals and plants can arrive on the scene later, you have to change the earth such that it is hospitable to animals and plants.

So why aren't there any animals or plants etc. that lack ubiquitin?

Because it was just good enough to work. As you said, a "frozen accident".

Yes, but that does not explain why there are no eukaryote lineages that lack ubiquitin.And, again, from a front-loading perspective, we would predict ubiquitin homologs in prokaryotes, while we cannot predict this from a non-teleological standpoint.

But there is evidence of accidents and no evidence of front-loaders.

That's not really the issue IMHO. If we assume, for sake of argument, that the Metazoa we see today was the intended outcome of a front-loading scheme, we can make testable predictions regarding biotic reality. This is the point. Confirmation of those predictions strengthens the above thesis.Now, you might rightly ask why we should assume that Metazoa were the intended outcome of front-loading, instead of, say, a race of flying spaghetti monsters. But here is where fallible intuition comes into play. If we were to seed another planet with life, and front-load objectives into existence, we would likely choose plants and animals. This, of course, is not evidence that Metazoa were the intended outcome of front-loading - I am well aware of that. However, if we follow the line of thought that Metazoa were, in fact, the intended outcome of front-loading, from here we can make real predictions that are not made by the non-teleological model. The non-telic view of life does not require that prokaryotes have ubiquitin homologs. Darwinian evolution has been very comfortable with the fact that, prior to structural analyses, there were no known prokaryotic homologs of ubiquitin. Yet front-loading predicts exactly this.

Why should anyone assume that there was ANY intended outcome?

There are clues that teleology has played a role in the history of life on earth, so this offers a subtle hint that maybe there was an intended outcome.

If my Rain Dance causes the rain, then I predict that it will rain after I do my dance. It did rain after I did my dance, therefore that strengthens the theory that my Rain Dance causes the rain.Would that lead you to believe in Rain Dances?

No, because rain is predicted from plain ole' meteorology.