I've been very curious about Life for my whole life. I'm 45 years old. There have been a lot of theories about life, ranging from religion to accepted, and unaccepted, science.

When I look at our world, I see a chain of life, and I don't see a difference between organic and inorganic matter. Eventually, when you trickle down anything biotic, eventually it becomes chemicals that are not self-propigating.

If you think about autotrophs and heterotrophs, Life makes sense, and in a certain sense, you can say that even organic matter (Life) is inorganic (evolution-wise).

When I wake up every day, and walk down the street, and see a rock, I don't think how different it is from me, I think about how much we have in common.

I guess my question is, is it insane to see inorganic and organic matter as being 2 modes of merely being?

Why do we make the distinction of organic vs. inorganic? Its all one big system.

"Organic" has a specific scientific meaning -- it refers to organisms that are alive and can reproduce, passing on their own form via DNA. Some things (animals, plants, bacteria) can do this; other things (rocks, clouds, mountains) can't.

So organic and inorganic substances do of course have much on common -- both are composed of matter -- elements, isotopes, molecules, etc. -- and are acted on by forces (gravity, electronmagnetism, etc.) But they have a very fundamental difference, and that difference is reproduction.

Agreed Mike but this is to a certain extent semantics - yes right now the ability to replicate is confined to the organic/"living". When or if we can take chemicals and create/build a cell that can replicate then at that point I tend to agree with Shawn - it would then be a continuum rather than two discrete classifications.

I am also conscious that this discussion is now much closer to philosophy than biology!

Shawn then posted again


I'd just like to say thank you to David and Mike for answering my previous question.

It seems that there is indeed a valid reason to separate organic from inorganic matter, in that one can generate new, unique versions of itself, and the other can not.

I suppose my philosophical mind got the best of me, and indeed reduced this distinction to an absurdity (ie not recognizing the difference between life and non-life).

My goal, however naive, was only to reduce separation and promote inclusion. As with most of my questions (and they are questions, as I truly have no answers) I look at biology and biological evolution as being the root of everything, so sometimes I suppose my thoughts become incoherent.

Thank you, again, Mike and David, for reigning in my thoughts.

And thank you for bearing with my incoherence.

Shawn

"When or if we can take chemicals and create/build a cell that can replicate" ...

Woah! Surely that would merely be another instance of organic material?

it is all really semantics!

I think the question is suffering from two pieces of baggage (not of Shawn's making mind you):

The split is largely a hangover from earlier scientific thinking (strictly speaking "organic" and "inorganic" are usually used for chemistry, not so much for "living" vs "non-living"), which in itself inherited some classic (but wrong) categorisations of the world.

The more we know about life, the more we understand that there is no clear cut off (at least going back to the origin of life) between when chemical reactions were just happening, and when they became part of a living organism. Indeed, I think the distinction is missing the point: there is NO distinction. Today we find the distinction mostly clear, but we are looking at billions of years of evolved organisms compared to a rock; but we get confused when we try to categorise viruses.

I think we fall victim to what Richard Dawkins calls the "tyranny of the discontinuous mind": humans have a tendency to need to neatly package the world into separate categories, and we struggle when characteristics occur on a continuum.

"The more we know about life, the more we understand that there is no clear cut off (at least going back to the origin of life) between when chemical reactions were just happening, and when they became part of a living organism. Indeed, I think the distinction is missing the point: there is NO distinction."

Really? Have we found intermediates?

I think that most groupings that humans impose on nature are largely due to the pragmatic need to be able to talk about it in a clear way; which is very useful when carrying out and discussing science, but creates a false sense of things being as clearly distinct in nature itself.
Take the evolution of species: for example when one species splits into two, if you were able to be present during the whole process, is there a clear point when the one species becomes two? Most likely you could never point at one single point in time where that happened.
There are many other continua like that, especially in biology.
The origin of life, I would say, is also such a continuum. However abiogenesis unfolded, it seems that the transition from basic chemical reactions to a living cell (especially one at this early point in evolution) would be a gradual affair of increasing compelxity and self-containment. Do we need to draw a clear line at some point in this process beween non-life and life? That probably depends on what you are trying to achieve: if it's for pragmatic purposes (say we want to have a definition of life so we know when we see it on another planet), then that's fine; but in reality, I think being clear that there is not objective distinction in such a scenario is important for our understanding of how it works.
That's not to say that a rock isn't clearly non-living, which a bacterium is clearly living.

Shawn then posted again


I just had a big chat with my brother, who is a nurse/scientifically educated. He started:

Faith is an act of courage - not a religious principle. There is far more to this - we respond to the world around us through our senses and nothing else. What else do we know besides that which we sense? I cannot trust my own thoughts, but when I articulate those thoughts to another they are heard and felt, only becoming real at that moment. Let the feeling out. Non-immutable knowledge be damned. We are nothing without having shared how we feel.

I had to reply:

We can share how we feel without stating that what we feel is the truth. Life is so vast that being humble should be the way of things. By routine, scientists say "I don't know" and then they spend their entire lives trying to find the answer, usually with failure. Those who hold faith higher usually find no answers except those they already believe and are incapable of changing in light of proof. Science is a bigger act of courage than faith - faith has all the answers; science does not.

.......

What I'm learning is, my respect for science is even bigger than Darwin or Newton or Planck. It's about the average scientist who can say "I don't know", who tries to move forward to advance knowledge.

Rolf,

I fully understand (and needless to say agree) that the transition between one species and another is a continuum with no clear boundary except the one we draw. The part of your answer that I found more surprising was this:

"The origin of life, I would say, is also such a continuum. However abiogenesis unfolded, it seems that the transition from basic chemical reactions to a living cell (especially one at this early point in evolution) would be a gradual affair of increasing compelxity and self-containment."

What is the evidence for your assertion of a continuum between non-life and life? Have we observed intermediate stages? (To be clear, I'm not disagreeing with you about this, I don't know enough about it to do that -- just trying to understand what we actually know.)

I'm not sure if these fit Mike's request for intermediates between life and non-life but some perennially troublesome categories would be viruses and prions. Both fail the full set of criteria for life in most people's books - but for viruses only be a small margin!

It is also true to say that one can engineer self-replicating entities in a computer than evolve (as simulations, computer viruses etc) and it does not seem to me too far into the realms of science fiction that we could have self-replicating entities with AI and (perhaps) physical form. Would these be alive or not? They could easily be engineered to meet the traditional "criteria" for life. I guess mt point here is that if we've long had entities that are troublesome to categorise (viruses), things may get even more difficualt in the near future!

I know viruses are in a grey area -- but of course they're no use as an evolutionary intermediate since they can only reproduce with the help of unambiguously alive organisms.

>since they can only reproduce with the help of unambiguously alive organisms.

I know what you mean (and totally agree) but just to be pedantic and illustrate where semantic fuzziness can creep in ... as worded, the above statement is (arguably) also true for all autotrophs since reproduction is energetically costly and animals have to eat other unambiguously alive organisms to address this energetic need.

And - just chatting with a colleague who works on viral evolution. He would have no problem with viruses being called "life" but isn't really hung up on it either way. It does turn out that our view of how limited viruses are is changing very rapidly. Below is a nice lay article.

http://www.the-scientist.com/?articles. … onsidered/