I know I’ve talked about this before on this blog, but I can’t get my hands on any essays I’ve written about how life is defined and how this question remains a longstanding topic of discussion between me and my wife on what makes something alive.

bacteriophage

I feel fairly confident that we both have a pretty good grasp on what the arguments for and against something being called ‘alive’ are. It’s not the characteristics of life that we dispute, but how much weight each of them should carry.

pooch

As a bit of background, it should be stated that even biologists have a fairly difficult time defining life formally. Many of us can point to a rock and declare ‘not alive’, to a dog and declare it ‘alive’, etc. But these are simple examples. The things that really challenge the definitions are where details and technicalities become sticking points.

The two standard tests of life can be summarized as:

1. The Cell Theory – The cell is the basic unit of life and therefore all life must be cellular.

2. Defining life as things that have ‘The Characteristics of Life’:

a. Life must be ordered

b. Life must reproduce

c. Life must metabolize

d. Life must be homeostatic

e. Life is evolving

f. Life responds to stimuli

g. Life must grow/ develop

My wife has a much more comprehensive view of what it takes to be called alive. She would like to see most, if not all of the seven characteristics of life fulfilled and also holds to all life being cellular. When pressed, I think that she finds the most value in defining life as those things that can metabolize for themselves. They may require certain environmental support (waters, food, etc.) but when given these things, they can meet all the characteristics of life… but metabolism seems to be one of the most defining of these characteristics.

I’m not sure if holding to this definition represents any specific school of thought, but I suspect it reflects an organismal approach to life informed by her history as a clinician.

I, on the other hand, have a much more minimalistic definition of life that elevates the importance of reproduction over most other characteristics. If a thing has genetic material of some sort and can reproduce this material resulting in new life, that is sufficient for me – even in the absence of many other characteristics from the list above.

Why is this so important to me that reproduction trumps all else? I wasn’t sure what it was until I got to thinking while listening to Richard Dawkins’ newest book, The Magic of Reality. I’m listening to it for a number of reasons, perhaps primarily because I am developing a new course for the Summer semester that examines the philosophy of science. However, Dawkins hits upon many of his standard points in this book, one of which is, ‘we are all simply machines built by our genes, for the sole purpose of perpetuating those genes.’

There it is, a molecular definition of life. A definition, which although I was not always consciously aware of it, was critical to the way I approached biology. In my head, all living things are just self-replicating molecules wrapped in complicated shells (bodies). It’s really just the DNA that is alive.

This is exactly the opposite definition as that held by my wife. She views the organism as a whole as the primary unit, that thing which is really alive. One comment that she made that clarified her perspective to me the most was that it’s really not as important to talk about what is alive and what is not, as it is to talk about what has consciousness and what does not. I think this is really cool, it’s almost like an eighth characteristic: awareness. This is not to say that things cannot be alive just because they are not self-aware, but to add something new and elevate the definition from mere life to something more. Something relatable.

I think it’s important to remember that this is really a philosophical point. As such, the answers are not as easily classified as right or wrong, but merely as points of view.

We have also talked a lot about how language shapes the way people think. We both agree that this is possibly one of the major differences amongst people of various cultures. Some people speak languages that place more or less importance on things (one example we discussed recently was that some languages do not have a future tense that distinguishes it from talk of the present tense. This may impact how certain cultures value the future more or less than others … think saving for retirement). Some people benefit from being multi-lingual and therefore having many frames of reference, or lenses that they can view current events through.

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I bring this up because she started her professional career as a veterinarian, caring for animals, curing disease, controlling chronic problems, managing pain. The animal was the focus. I, on the other hand, began my professional career as a molecular biologist, snipping out genes, cloning them and expressing them in different organisms. The genetic material was the focus.

Just like language, our careers shaped our approach to life and allowed us to define it from very different perspectives.

People are funny that way.