Volume 1, Issue 1 
1st Quarter, 2006


Astrobiology: What Are the Characteristics of Life?

Barry Blumberg, Ph.D.

Page 5 of 7

Metabolism
Living matter has to do something. It just can't sit around, at least forever, in order to be considered living. So that means it has to take something from the exterior, internalize it, convert it into energy, in order to move, reproduce, produce, think, plan.

Still, some living things can go into dormant stages for years. Bacteria and fungi and yeasts in some cases can stay dormant for centuries and they have the capability of coming alive. So when you see them during this dormant period, they don't have many of the characteristics of life, but they're alive because they have the potential of life. You have to question, "Is this thing alive?" And the answer is, "Well, how long do you want to wait to find out?" So, again, this idea that you have an active process going on all the time, that in itself doesn't define life. 

Now, nutrition is alive with the idea of metabolism.  If you seal any living thing in a closed box and isolate it from the rest of the world, the cosmos, it won't remain alive.  So a life form must be surrounded by nutritional materials that can contribute to this metabolism that creates the energy that allows living processes to continue. 

Complexity
All living organisms are complex. Even the smallest and most minute ones. For example, consider E. coli, which is a pretty small object Blumbergand pretty simple, a single cell. There's ongoing research about E. coli because it turns out that the more you know about E. coli or the more you know about anything, for that matter, the more you know about what you don't know. So that means the more you know, the potential for even greater complexity exists. This is different than physics, where the more you know, the more you try to simplify it to some kind of simple, central thinking or idea. 

Biology tends to love complexity and this is the characteristic of biological research, which can be disappointing to some. It doesn't mean you never answer all the questions; it just means there's a multiplicative effect.

So again, whereas physics and chemistry seek a kind of simplification, what you really want is more complexity because the more complex the subject, the more places you can intervene. Medicine is essentially an interventional science, that is, whatever is going on in pathology is presumed to be disadvantageous in one way or another and you want to intervene. The more complex the explanation, the more places you can intervene, so the last thing in the world you want is simplicity. When I go to people who make models of biological processes and ask them, "Can we model this?" and they ask, "Well, what variables can we get rid of?" I reply, "Wait a minute. I don't want to get rid of any variables. I want to keep them." But then it's very hard to make a mathematical model. And so we compromise.

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