Certainly, and I’m near certain in my opinion life will be found on Mars (if it wasn’t already). But what evidence, I wonder, is called upon to show Earth is modeled “fairly” as an isolated, or closed, system? Is there really evidence for this?
The matter of extrapolating from Earth's fossil records in order to estimate the possible distribution of hypothesised exo-life, is mathematically invalid unless one is of the view (opinion) that Earth is not modelled fairly as an isolated system - in which case, one would expect life to be found in an HZ fairly nearby - like Mars, eh ?
Whatever the case, I think it’s mathematically invalid to extrapolate much, if anything, from an example of one.
Agreed; we’re only now beginning to acknowledge how much a hand in evolutionary advance HGT (horizontal gene transfer) has had; a seemingly chaotic process.
The information systems understanding of the evolution of the human genome invariably involves chaotic processes … which results in unpredictability at certain scales, and predictability at others. The question then becomes one of the scale at which one is able to make second instance predictions reliable - if at all.
The author touches on this in the “author’s replies”:
This paper fits a logarithmic regression curve of functional non-redundant genome size vs time of origin in major groups of organisms, in order to extrapolate backwards to come up with the 10 Gy origin estimate. The fit is somewhat synthesised as they estimate genome size based on regression of this model from modern day genome sizes/complexity, (rather than direct fossil genome measurements). The graph in Figure #1 combines prokaryotes and eukaryotes, but the two had very different evolutionary trends. As mentioned, I don't believe evidence exists for how big the genome size was for early prokaryotes, so I doubt the model's credibility when it comes to real-life evidence bases. (The idea however, is only at the early hypothetical stages, so it is probably unfair to judge it on this basis alone).
I have addressed this problem in discussion by estimating the average rate of increase in genome complexity in Archaea and Eubacteria which appear lower than the rate of complexity increase in eukaryotes. Then I discuss 2 possible scenarios: (a) initial rates of complexity increase in prokaryotes were similar to those observed in eukaryotes and then slowed down due to organization constraints, or (b) rates of complexity increase in prokaryotes were always slower than in eukaryotes. With scenario (a), the expected origin of life is ca. 10 billion years ago according to regression (Fig. 1), and with scenario (b), life originated even earlier than that. Thus, separate handling of prokaryotes and eukaryotes does not bring the predicted date of life origin closer to present.
For all we know, the characteristic complexity of the prokaryotic genomes had been reached very early on during life's evolution (considering the geochemical and paleontological evidence of more or less modern-like microbiota ~3.5 billion years ago) and remained in equilibrium ever since. Thus, to the best of our understanding, there was an early explosive phase of evolution of complexity, which was followed by stasis (the prokaryotic phase of life's history) and then by another burst associated with eukaryogenesis.
Agreed, and this paper: ”Darwinian evolution in the light of genomics” discusses more what we know and what we might discover; I think it's a good companion piece.
Its certainly an interesting perspective though .. one well worthy of a few reads, IMHO .. and one to file on the shelf and occasionally review, as the thinking matures.
Yes, I agree there’s much yet to be learned but I suspect (for what it’s worth) ideas like this are in the right direction.
My overall feeling however, (for what its worth), is that imposing a power law relationship on some sketchy inference data, and specifically excluding the 'non-coding' parts of organism genomes, assumes a level of understanding of genetics, which I don't believe has yet been achieved in microbiological research areas.
Thanks for taking the time!
Where the telescope ends, the microscope begins. Which of the two has the greater view?