Organism Closest To Original "Tree of Life" Discovered

An anonymous reader writes "Scientists have discovered a benign algae eating protozoan in a lake near Oslo, Norway whose gene sequence does not match any known organism living on earth today, and this beasty combines genetic characteristics across plant, animal, and fungal kingdoms. It is believed to be the closest living organism to the original organisms that spawned all animal life on earth."

Comments

A bit of explanation to save you from RTFAing

[Samantha Wright]

Here's the paper.

And to ruin all of the surprise: it's believed to be about a billion years removed from other known protists. That's about the same age as multicellular life. Archaea are more distant from us than these protists.

This is more baseless conjecture than anything, but its blend of unusual genes most likely suggests that it is the sole (optimized) survivor of a larger ecosystem of similar strains, which may have exchanged DNA through some horizontal gene transfer mechanism in the past. The relatedness to a distant organism in Tibet implies that at least one of these species was once geographically ubiquitous, or spread through some other means, and may have blended into its surroundings there.

The measurement of the organism's "age" is based on the sequence of an extremely conserved gene that codes for a part of a very important cell component, the ribosome. That measurement reflects how many times the sequence has been altered since it last matched a suspected common ancestor with its nearest relatives. The researchers never said that it's been essentially the same organism for a billion years (although it looks that way in the summary and MSNBC article); since they only analysed live samples, not fossilized ones, there's no way of knowing (and I'd be sceptical about any claims that said we could sequence billion-year-old DNA.) At any rate, analytical genomics shows us that for the sequence to stay the same for so long, the environment would have to be completely static and the genes very specifically optimised, which was almost certainly not the case due to historical climate trends. The rate of sequence change is very reliable on a large scale.

Re:A bit of explanation to save you from RTFAing

[interactive_civilian]

In modern classification, there is no Protist kingdom. Protists are polyphyletic, which means they have representatives in many different groups (or Kingdoms, if you want), and each group is linked by a common ancestor. Though they are still working out the actual branches of the Eukarya tree (a lot of the early branching is difficult to resolve because of so much genome re-arranging and duplications, insertions, and deletions), one fairly recent paper suggests at least 6 "Kingdoms": Opisthokonta (which includes fungi, animalia, and some of what were previously thought of as protists), Amoebazoa (amoebas, slime moulds, etc), Archaeplastida (plantae, red algae, and green algae), Chromalveolata, Rhizaria, Excavata, and some groups that aren't clearly in those groups. This paper by Roger and Simpson from 2004 has a good summary:

Simpson, A.G.B. & Roger, A.J., 2004. The real "oekingdoms" of eukaryotes. Current biology, 14(17), p.693-696. Available at: http://kfrserver.natur.cuni.cz/studium/prednasky/bunka/2005/simpson_eukevol.pdf. (PDF link)

I'm sure there has been more work since then, but that paper is accessible to non-experts and a good overall read (though I recommend having wikipedia open to see what organisms they are talking about when they list names).

Modern classification is a bit of a mess, because Nature doesn't fit into the neat hierarchical classification system that we grew up with. A good example of this is the idea of the Animal, Fungi, and Plant kingdoms of old. If Animals and Fungi deserve their own kingdoms, then at the same hierarchical level, each plant "phylum" should actually be a kingdom. Or something along those lines. But anyway more modern classification uses monophyletic groups (groups in which all members have a common ancestor; e.g. Eukarya is monophyletic because all eukaryotes share a common ancestor, but Protista is polyphyletic because there are protists which have a more recent common ancestor with animals than they do with other protists).

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About the article, man that thing is a mess. Is it a translation problem, are the journalists who wrote it completely clueless, or are the researchers who discovered this organism extremely out of date with their classification? It reads more like a discovery from 1970 than 2012. :-/

Re:A bit of explanation to save you from RTFAing

[Anonymous Coward]

Pretty much. They're a garbage bag of mostly/variably single-celled eukaryotic creatures that don't fit into the traditionally multicellular kingdoms, such as animals, plants, and fungi. It's sort of what you'd be left over with if you took a big, branching tree (all of the eukaryotes) and lopped off large swaths of its branches. Eukaryotes themselves are a chimera-like mix of several bits and pieces (e.g., chloroplasts and mitochondria, which are thought to have been originally independent prokaryotic creatures: look up endosymbiosis). In the real world, classification is messy because life has had a rather complicated history.

Imagine the worst conceivable spaghetti code, built to merely a "good enough to still be self-copyable" code standard, and duplicated (with copy errors), forked (speciated) and merged (endosymbiosis, crossover, and sex) zillions of times with no centralized repository for a few billion years. Then humans come along and try to figure out the code history after the fact, and after 99% of the code has been thrown away (extinct). It isn't going to be pretty. We have a broad outline of the plot to the story, and that's it so far.

Wrong headline!

[Anonymous Coward]

It might be a basal eukaryote, but that does not make it basal life, i.e. bacteria and archaea were present on Earth for ~2 billion years before eukaryotes came about..

Re:Oblig.

[JazzHarper]

But... but... which day did God create that one again?

The fifth day. "Read your damn Bible."