Rainer Glaser, Brian Hodgen, Dean Farrelly, and Elliot McKee
‘Adenine Synthesis in Interstellar Space: Mechanisms of Prebiotic Pyrimidine Ring-Formation in Monocyclic HCN-Pentamers’
Article, Astrobiology 2007, 7, 455-470. PDF. (Publication in Print: June 2007)
Online Visualization: Chime Displays and Reaction Animations

http://web.missouri.edu/~glaserr/vitpub/adenine_ast_2006.0112.pdf

Part of it seems to depend upon where we choose to look, and on what scale. Cells of the body, and each one alive, composed of un-alive atoms? And we thinkers, an unlikely result of the collective efforts of these cells?

I suppose if a cell in our body might contemplate its existence, it would have to observe the things around it, or better yet, travel outside the body, finding, perhaps, a gargantuan being, beyond comprehension, scratching itself.

Or, if planets could talk to one another, might the Earth brag, oooo, look what I’ve done: look at my hairdo, as all we little critters now go springing out into the space surrounding it.

Everything seems so interdependent upon everything else. It’s all connected, if even just from the Big Bang. It makes me wonder if asking the question, is something alive, is really all that important. What does seem important, though, is a general respect shown toward all our constituency, and whatever constituency we might find ourselves a part, on whatever scale.

We have suns whose component processes manufacture carbon and metals. We have plants whose component processes manufacture oxygen. We have ourselves whose component processes manufacture thinking about stuff like this.

And we’ve likely got big clusters of all this stuff going on everywhere. I wonder, is a delineation between life and non-life anything? Or are we just looking for something we recognize to be something like ourselves — something we can, in some more intimate way, relate to? And if that’s the case, maybe it’s just as good to ask the question, what are we, to wonder such things, or to wonder at all?

Maybe we don’t really need to abstract ourselves from life to define what it is and is not, creating boundaries where none seem, on various scales, to exist.

I just love to death, though, that we really don’t want to be all alone in it all, though.

And even protists share many, many genes with multicellular organisms as large and complex as ourselves. Indeed, biology reveals a remarkable level of recapitulation throughout its putative history. What one sees with multicellular organisms is a new layer of complexity over what can be achieved with a genome surrounded by a membrane, and this arrangement is almost totally constrained by size, most notably the ratio of surface-area to volume.

I don’t think there is a “better” in evolutionary terms. When there is selective pressure (and even in its absence, due to genetic drift), life tends to fill up all the niches, but there’s no reason to expect any kind of symmetry in terms of number of species or mass of a particular species in those niches, and no value judgement we can readily place on such metrics so long as the species in question is viable from generation to generation.

Emergence, complexity, self-organization, and so forth are transparent revivals of the discredited doctrine of Vitalism.

Acute characterization – I haven’t seen it expressed so sharply before.

Evolution isn’t a “ladder of progress” or other misplaced Victorian concepts, but a symmetric process that can go both ways. The initial conditions was asymmetric, but after 3-4 Ga the majority of biomass is still simple Virus and Bacteria. Simple is better, and I believe biologists think that it is energy requirements that constrain size.

There is a coincidental tail diffusing towards complexity in lieu of the constraint pushing back. Simpler and faster reproducing Bacteria have outcompeted Archaea to inhabit extreme environments and Eukaryota to exhibit complex phenomes. As these things go, we are the scum of Earth.

I agree with Jason Dick that a functional description is better. My own motivation is that it fits established theory better. Also, in biology distinctions are fuzzy. For example, we are forced to use several species concepts. So we can and probably must use several life concepts.

[For living sexual populations we can use the "biological species" concept. (Different populations who can't or won't mate belong to different species.) But that doesn't describe asexual populations or fossils.]

Therefore I propose the following modern concept of life (in analogy with “concept of species”):

An organism is the unit element of a continuous lineage with an individual evolutionary history.

The model for the definition is an organism as the current slice in a continous process. Thus combining the idea of life as individual and life as process with evolution and an implicit assumption of am inheritance mechanism, and a robust definition of organism. Quite a few birds knocked down with one stone.

This definition excludes organelles and such replicators as prions because they have entered dependent niches, as they are subsumed into an organism. But viruses are individual organisms under the definition, as they coevolve instead.

Similarly such things as memes, stars and galaxies are excluded, as they have no inheritance. While software/hardware such as implementations of genetic algorithms are included. (As noted, such populations may or may not inhabit other environments than we do.)

Finally, to amplify:

Viruses and cells from different extant and extinct domains could have crossed the Darwinian threshold several times from a progenotic state. Also, early total extinctions are consistent with the observation of early and so likely easy abiogenesis.

These crossings are initiated by diverse selfish elements, a mechanism that is often observed in genes. Evolution, especially past a progenotic state, is a competitive [sic!] and robust process which we should expect to be common elsewhere.

Maybe we will meet singular existences, biological or mechanical, that aren’t described thusly. But I believe the way to bet is that they are rare and bound on an extinction path. We could probably approximate “life” with “populations that obey evolution” as above. Other characteristics are coincidental.

B, I agree it looks like we sort of agreed all along, we just misunderstood each other. I still maintain that it is strictly improper, according to the laws of language, to use a word in its own definition. You never see this in a dictionary (unless the word is referring to an above definition of the same word).