Why Scientists Think Completely Unclassifiable and Undiscovered Life Forms Exist

An anonymous reader writes: In a new paper published in Science, researchers at the Department of Energy's Joint Genome Institute note that "there are reasons to believe that current approaches [to discovering life] may indeed miss taxa, particularly if they are very different from those that have so far been characterized." They believe life forms exist that don't fall into the established eukaryota, archaea, or bacteria kingdoms. They argue that there may be life out there that doesn't use the four DNA and RNA bases that we're used to; there may be life out there that has evolved completely separately from everything that we have ever known to exist; there may be life that lives in places we haven't even looked.

Comments

Have we discovered all there is to discover?

[QuietLagoon]

Of course not.

.
To think that we have discovered all there is to know regarding life forms would mean that we already know all there is to know in this field.

So maybe we need to use different methods than the ones we have been using. Makes sense to me.

Re:Have we discovered all there is to discover?

[Anonymous Coward]

And just to pick a nit a bit:
"Unclassifiable" is pure nonsense. Unfamiliar, sure. Foundationally different than all terran life, sure. Unclassifiable, no. Even if it just starts a conversation that leads to a decision to add a larger category than 'kingdom,' once recognized, it can be classified.

Re:Have we discovered all there is to discover?

[Applehu Akbar]

What they mean by the term is "not fitting existing classifications" of course.

Re:Have we discovered all there is to discover?

[smellsofbikes]

Indeed. We have enough trouble finding certain DNA-based life forms. Plenty of life forms we only know about because we leaned how to copy DNA, and started grinding up samples and amplifying the DNA. Many of those refuse to grow in petri dishes and don't cause diseases, and would no doubt be unknown to this day if they didn't contain DNA.

I think there's a fairly low chance that Earth has life that doesn't use DNA/RNA but if there is and it minds its own business, it could be decades or more before we discover them.

Consider things that grow much, much more slowly. They're already finding chemolithoautotrophs living in rock 4 km beneath the surface of the earth, that reproduce over the course of years, rather than in twenty minutes like the bacteria we're used to working with. If there were organisms that didn't have DNA, but did have some sort of body that could maintain chemical gradients, allowing it some sort of metabolism, and reproduced on the scale of centuries, we'd have trouble ever noticing it was there because we haven't made the tools to find it, for lack of knowing what we're looking for.

is this news?

[Triklyn]

I was under the impression that news was about you know, new things. This is just an article highlighting that money has up until now been targetted toward things we are pretty sure exist. you know, novel creatures not using radically different genetic bases. This is just some dudes going, "yup, there might be more out there than we thought" which is you know, the basic premise of all the sciences.

Come back to me when they actually find something that uses a sixth nucleotide.

Incidentally, where might this new life have hidden, that we haven't searched already. We've got extremophiles in the middle of godforsaken rocks already... there aren't that many new places that i imagine we

A. haven't looked already
B. aren't already colonized by the cousins we know.

Generally speaking, the new life would need to be able to outcompete, in certain circumstances, the stuff we know or it wouldn't survive too well the 2 billion years that bacteria have dominated the planet.

i'd think the only viable thing would be viruses, maybe, and us not fully understanding them. but then i'd imagine if an different nucleotide were somehow incorporated into a virus we'd already found, it'd also be present enough to show up as an unknown nucleotide. Might not know what it was, but we'd most likely have an idea that it were there.

Re:Discover life?

[wierd_w]

Historically, "Life" has been defined as being any phenomenon that possesses all 5 life processes:

#1 Food intake/ nutrition
#2 Respiration
#3 Excretion
#4 Growth & Repair
#5 Reproduction

However, this seems to have been expanded to 7:

#1 Movement
#2 Respiration
#3 Sensitivity
#4 Growth
#5 Excretion
#6 Reproduction
#7 Nutrition

This is for "Life" in the generalized sense, fully abstracted away from any specific mechanisms by which those processes may be achieved. It is perfectly sensible for an artificial lifeform to be constructed, as long as it is able to fully carry out those processes. It needn't have any organic components whatsoever.

Nowhere in the historical definition of "life" used by life science is there a requirement for specific mechanisms-- just processes.

"Generalized Life"

[radtea]

Massive generalization has been good to the sciences.

In physics, we have used invariance principles to expand our definitions to the most general possible. This was the argument behind General Relativity, for example: Einstein wanted equations of motion that would be invariant under any smooth second-order transformation whatsoever, and when he put that constraint, and only that constraint on, he found the most general form of the equations of motion were uniquely determined (up to a constant of integration, which is the Cosmological Constant).

Biologists have generally shied away from this kind of approach to their field, but there is an argument to be made that there is an equally general definition of "life" as "anything that participates in a process of evolution by imperfectly heritable traits that result in differential reproductive success". It need not be tied to any particular concrete mechanisms like DNA and RNA.

This idea may turn out to be silly (which is why I wrote a novel about it rather than a scientific paper: http://www.amazon.com/Darwins-...) but well into the 1800's there was no general view of "energy" that unified all the disparate forms, to the extent that the fact that light had energy that was in any way related to mechanical energy was not really appreciated. The kind of unified view of energy we have today would have seemed bizarrely speculative at that time, in the same way that the notion of a unified, generalized view of life is purely speculative today, but it turned out to be amazingly useful, so it's worth considering the possibility in biology today (anti-science people will likely attack it as a waste of money, using computer technology that would not exist without a similar "waste" on ridiculous fantasies like quantum theory and "obviously useless" research into the basic physics of semi-conductors in the past.)