4-Billion-Year-Old Fossil Protein Resurrected 84
First time accepted submitter Zoë Mintz writes "Researchers have 'resurrected' a 4-billion-year-old Precambrian protein and found they resembled those that existed when life began, proving that protein structures have the ability to remain constant over extended periods of time."
Re:Alive (Score:0, Interesting)
It is implied by the usage of resurrected.
Re:"resembled those that existed when life began" (Score:5, Interesting)
I can't sort out why. The statistical tools they used seem little different from how the proto-languages of major language families are reconstructed. In both cases you look at the genomic unit (in molecular biology that is genes and the proteins they encode, in comparative linguistics it's words, or more specifically cognates). In either case you cannot state with absolute certainty that the proposed progenitor unit (gene or cognate) has been reconstructed absolutely, but you can say with a reasonably high probability that you're pretty close.
Re:"resembled those that existed when life began" (Score:5, Interesting)
I didn't mean to say they were identical, but still, at least in the Indo-European languages (and I'm sure it can be found in other language families) there are some pretty highly conserved cognates, like pHtér (father). In most cases throughout the various Indo-European families one can trace pretty predictable sound changes to explain why pHtér became pater in the Italic languages. pitár in Sanskrit and father/fadar in the Germanic languages. Yes, there's a good deal more horizontal transfer in languages, and indeed in some cases words will disappear from some members of the family, but in general, the core vocabulary of the proto-language is pretty highly conserved in its descendants. Even in English, with its vast importation from the Norman invasion onward of Romance and Greek words, the core vocabularly remains Germanic, and the sound shifts from the Proto-Germanic thru West Germanic thru to Modern English tend to follow regular rules. It's actually kind of cool, because even where you have a word that was adopted from another language, you can usually determine when roughly it happened by the way in which it was or was not effected by the sound changes going at the time.
Re:"resembled those that existed when life began" (Score:4, Interesting)
For some reason, that bewilders a lot of reasonably scientifically-minded people.
Just because you can come up with one or more best fit versions from what currently survives, doesn't mean that they resemble the original source of the evolutionary pattern.
Re:Sorta (Score:5, Interesting)
The LUCA dates range from 3.5 to 4 gya, so it's even broader than that. Different estimates come from different sources and with different precision, though, so it's not quite right to give a single symmetrical error measurement. I'd personally vote for saying 3.8 +0.2/-0.3 gya. In the case of this article, however, they chose 4 exactly because of their molecular clock predictions.
The article doesn't clarify between the Archean and Hadean periods, however, and it's probably bad to equate the LUCA with the beginning of life because we have pretty strong evidence that the LUCA was already a very well-developed organism, with a complete central dogma, hundreds of enzymes, and a preference for potassium ions over sodium ones. Wikipedia cites several science journalism pieces that argue for a Palaeoarchaean LUCA.
As for what the LUCA actually looked like, I would say somewhere between Archaea and Bacteria, but defying both categories. Archaeans have a number of later innovations that definitely disqualify them from being good representatives, since they can do sophisticated chromatin modelling (folding DNA to make gene transcription more efficient) and have a unique membrane composition (which I personally like to imagine may be evidence of multiple abiogenesis events, but that's a bit of an uninformed theory.) Bacteria, on the other hand, are known to have a tendency towards simplifying their genomes. If anything the bias seems to be toward Bacteria as the root; no one has recently proposed that Archaeans pre-date Bacteria.
Re:Sorta (Score:5, Interesting)
Mitochondria are thought to be a (relatively late) Major Event - the genetic and biosynthetic pathways were already fairly advanced.
The major idea behind a LUCA is that you can 'work the clock back' with DNA sequencing to something around 4 billion years ago AND that all life-as-we-know-it relies on a fairly specific set of chemical reactions. It's pretty clear that modern organisms are a mismash of A+C+B+x - nature hates to throw genetic material away. It's also perfectly reasonable to assume that life started / stopped multiple times and that bits of earlier life were indeed incorporated into later critters. When you start talking about that, you get into some terribly annoying semantic arguments (perfect for Slashdot).
The Holy Grail would evidence of organisms using wildly different chemistry (like incorporating arsenic into the DNA backbone [arstechnica.com] instead of Phosphorus) or some molecule that transferred genetic information without DNA or RNA entirely.
This is one strong reason why we should get our respective asses towards Mars. It offers the closest laboratory for finding off-world life. What that looks like (if it exists) is going to be one of the biggest scientific discoveries ever.
So, for life on earth, it's pretty clear that there is one LUCA - something started us along the pathway to RNA and DNA based life (I'm personally a proponent of RNA World [wikipedia.org]). And TFA implies that that this enzyme was present fairly early on. But something further back had to set the stage for the ability of an organism to fold amino acids into proteins, etc. TFA doesn't even begin to discuss what the chemistry would have been - that''s another story - but by the time Thioredox was on the scene, something was making RNA and there was something that looked like a ribosome - pretty advanced functions. How they got there is pretty much hand waving.