So recently I stumbled across this interesting paper, in which a complexity analysis of the genome is extrapolated backwards in order to yield an origin of life some 10 billion years ago (and consequently, not on Earth, implying Earth has been seeded by panspermia). An offshoot of this is an answer to the Fermi paradox: intelligent life is in fact just now developing in the universe (it took that long to get to the necessary complexity), so we are probably among the first.
However, I have some doubts about the hypothesis, but lacking the biology background, I can neither substantiate nor dispel them.
First, the complexity measure they use: is it reasonable to measure genetic complexity this way? Obviously, a simple gene count is out, since even some bacteria then rank higher than humans. Thus, they measure the complexity using functional and non-redundant DNA sequences. But is this in general well enough understood to yield a good proxy for complexity?
Second, is the observation of exponential growth of complexity supported by theoretical models of evolution? They discuss various related points, but I’m not really competent to assess their discussion.
Third, they extrapolate the complexity backwards to zero, marking this point as the origin of life; zero complexity basically corresponds to a single base pair. Is this a viable criterium for ‘origin of life’? They discuss a model of abiogenesis in order to substantiate this; I’m roughly familiar with RNA world, which seems very different. Is their model plausible?
Fourth, are theories like this one well known, and generally considered mainstream? Or is this something better classified as fringe science?
I’ll take a quick stab at it, though genomics and evolutionary biology is out of my bailiwick.
Basically, they extrapolate the Origins Of All Life from only five (!) data points. The points they picked seem entirely arbitrary and without explanation: the origin of prokaryotes, eukaryotes, “worms”, “fish”, and mammals, and their respective genome complexity. That’s a seriously bullshit, antiquated perspective, considering the evolutionary history of all life as a “ladder” that leads to us at the pinnacle. How do they assign a single figure to the genome complexity of “worms” or “fish”? They don’t say. They just throw up Figure 1 by assertion, draw a line between some points that they don’t bother to explain and decide that’s good enough reason to babble about how life could have existed for billions of years before our solar system.
Actually, most of this horseshit was previously published here, including reviewer comments that make for entertaining reading. E.g., “This paper is an example of how not to analyze data.” which is as close to “fuck you” as you can write in reviewer comment.
You should always be at least a little bit suspicious of any sort of extrapolation. You should be more suspicious if the fit is anything more complicated than a line, if there are a small number of data points, or if the quantity being extrapolated is difficult to quantify. Even if you do have a well-justified model that’s well-overconstrained by the data and which fits all of the data very closely, you still need to justify the assumption that the conditions in your data set are similar to those in your extrapolation region. If anything, I’m surprised that the “10 billion years” figure they find is so close to the standard 3.5 billion year figure.
I’ve just skimmed the abstract, but from that it would be charitable to characterize it as fringe science.
Note that this is a non-peer reviewed pre-print, and was “self archived,” that is posted by the authors themselves. There is no external validation.
Regarding the previous article linked to by lazybratsche, it was “published” in Biology Direct, and open-access journal that employs open review. Their standards for publication are:
As lazybratsche notes, although the three reviews acknowledge that the article has some scientific substance, all three are negative. Sample comments:
Yup! Me being suspicious was the reason for this thread.
In any case, thanks for the replies so far; seems like I won’t have to bother with the paper anymore. However, there’s a few (mostly unrelated) points I’m still curious about: is there a sensible measure of genetic complexity? I would think considering something like the Kolmogorov complexity of a genome might give a good indication, but that’d be hard to approximate. And how about their ideas of abiogenesis? Usually (speaking from shaky memory here), I think one starts from some more complex point than their ‘single base pair’. But would doing so be viable?
[QUOTE=Mark Twain]
In the space of one hundred and seventy-six years the Lower Mississippi has shortened itself two hundred and forty-two miles. That is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oolitic Silurian Period, just a million years ago next November, the Lower Mississippi River was upwards of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-rod. And by the same token any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three-quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and a mutual board of aldermen. There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
[/QUOTE]
The paper’s science is only marginally better than Twain’s. I mean, as a quick back-of-the-envelope calculation, it’s not completely uninteresting, but when such a calculation gets an extraordinary result, the obvious conclusion is that the calculation is off, not that significant portions of geology and biology are in error.
The universe is about 13 billion years old. Life must have originated some time after that.My suspicion is that they’re a bit lucky to have hit within that range. I’d guess that equally 'valid" extrapolations could easily find a point before that.
I don’t know if there is a good measure of genetic complexity that would mean very much. Clearly we can count nucleotides or genes or whatever so that we get many ways to measure the complexity, but there’s no reason that an animal with twice the genetic complexity is “better” “more recent” “more evolved” or anything else with meaning.
I think -at best - you’d wind up with something like the relationship between brain size and intelligence. Yes, things with bigger brains are generally smarter but, no, you still can’t measure IQ with a scale.
As for starting with one base pair… technically you do start that way under the current theories. You might have to build up to a certain number before you get proper replication, but abiogensis theories usually assume a soup of randomly combining non-replicators that eventually form something that does replicate.
Could this paper have provided a reasonable conclusion that it is not impossible for life to have started before the earth was formed? If the analysis had reported the opposite, that life could not have existed prior to the earth’s formation would it have different significance?
Papers I’ve read in the past tend to look at either the number or percentage of unique sequences in the genome. Highly repetitive sequences, like satellite repeats or transposable elements, are simple, while unique sequences like protein-coding regions are more complex.
The Yahoo link to this paper mentioned Moore’s Law, which made me look at it. Moore’s Law is of course only an observation, not a law at all, and must have been included to make the paper sexier. The real deal is the so called exponential increase in complexity, as measured by functional DNA. Which leads to a few questions:
Where are the reptiles on their chart? If dinosaurs, for instance had the same amount of functional DNA as mammals it kind of blows their curve to hell.
When measuring the DNA of fish, are they counting modern fish or fish just after fish evolved? How do they account for the massive amounts of fish evolution in the last hundred million years or so? How do they measure functional DNA from fish fossils anyway?
Since we’ve just discovered that much of our supposedly junk dna is functional, how to measure functional dna in genomes we haven’t sequenced yet? There was an article in the Times yesterday about sequencing some of the dna of a coelacanth, which has 2.8 billion base pairs, close to us, which revealed a gene which might explain the development of limbs. They would like to have done a lungfish, but that has 100 billion base pairs, and is beyond our capability. I suspect our authors do not know how much of that is functional.
I wonder if these guys every submitted this to anyplace real, or if they knew where it belonged.
Accepted that this paper is junk - and also accepted that the method described above is a potentially valid method of measuring complexity.
IF a group had genetic material preserved from organisms ranging to at least a few million years back (something that is not completely impossible to someday occur), could any “complexity analysis” approach give any sort of meaningful extrapolation?
Just off the top of my head, I would strongly doubt it. There are just too many variables that we cannot measure. Rates of evolution or development of complexity are almost certainly going to change drastically over time. Considering that for most of life’s history, single cells were all that was around, any extrapolation is going to be based on a lot of guesswork. I certainly wouldn’t want my PhD to depend on figuring it out.
From the abstract, … there was no intelligent life in our universe prior to the origin of Earth, thus Earth could not have been deliberately seeded with life by intelligent aliens…
Seems like a pretty bold assertion. By the numbers, the universe was about 9 billion years old when the earth’s accretion effectively culminated, and intelligent aliens would not “seed” the earth at that time but would wait for life-supporting conditions to start to develop. Hence, the earth could have been seeded after the universe had had time to form intelligent life, 3 billion years ago. By their oh-so-stellar (!) math.
