Are viruses alive?

Ever since I was a kid I have wondered what living beings are. What exactly is the difference between a dog and a rock? Are they made out of different stuff? How did they come to be? For the longest time (till the age of 12) I believed that dogs and rocks are simply made of different stuff. Nobody taught me that. It just made kind of sense. Rocks are hard and stationary, whereas dogs are furry, they have muscles, and are full of energy. They are just different. When we learned things like "human body is 65% water" the confusion started creeping in.

When I got older, I started to understand that our bodies are made of the same stuff as all other inert material - carbon, hydrogen, nitrogen, oxygen etc. I heard statements like "scientists simulated early earth conditions, and amino acids (basic building blocks of life forms) were generated." I could not bridge the gap between molecules and life forms. How can presence of bricks mean buildings can be formed?

The more I knew, the more questions were formed. If plants are living, being then that means movement is not necessary for something to be alive. But how did living things come to be? When? Why?

All my questions were answered when I read the "The selfish gene" by Richard Dawkins. If you have not read it, please do. It paints a picture, a possible pathway of how molecules evolve into complex living organisms. (description of replicator to living beings journey).

Once you understand this the whole living versus non-living question is seen in completely different light. If you imagine your lineage far enough back, your ancestors will slowly start looking different and different. And at one point you will come across the original replicator molecule. You are certainly alive. And your hundred-million odd generation ago ancestor is a molecule. "He" is not alive. The question is, where do you draw the line? At what point in this lineage do you say this is where "alive" begins and "non-living" ends?

This problem is not trivial. It arises in the first place because like any other gray matter, this is a continuum. We discovered some obviously living beings, and some obviously non-living beings. We created the classes, the words, first and then started to populate those classes. Anything that we come across, now necessarily needs to go in either one of them.

Even the qualities that we associate with the living are not polarized quantities. Let me list some of the obvious ones.

Ability to move, to reproduce, to consume energy. But even these three are not without problems. Fire consumes energy. Fire certainly moves. And yes, it does reproduce itself. You can construct the same argument for water. I am not trying show that fire and water are living entities. What I am saying is that we do not have any specific objective test that tells us that something is alive.

Beyond these three the others start becoming little questionable. For example some definitions of life include
(Invitation to Life,: H. Curtis and N. Barnes, Worth Publishers, 1994)
1. They have the capacity to replicate themselves.
2. They have enzymes, and complex proteins essential for the chemical reactions needed for life.
3. Have a memebrane that separates the cell from the environment and gives it a distinct chemical identity.

The number 2 and 3 in this list smack of attempting to cleanly break the long chain of ancestors down into two classes. However the words "enzymes, proteins" imply a specific type of life. The need for a membrane and mention of cell is simply an attempt to draw a line in the sand. You and I don't have a "cell membrane", our cells do. We have skins. So according to this definition, you and I are alive, at the same time the billions of cells inside our bodies are life forms on their own. They do divide and replicate, you know.

The truth of the matter is that no matter how finely or broadly you try to draw lines, it is not possible. It may be useful to draw the lines somewhere. But we have to keep in mind that instead of making two buckets like living and non-living, we must accept that we what call "aliveness" is a continous variable. It is not a 1 - 0 property. Each entity has some properties of being alive. So you can probably assign a score that goes continuously from 0 to 1 and say that there is some degree of aliveness.

This sounds strange, but the strangeness is due to our predetermined conception of having two buckets - dead and alive. Yes or no. We don't entertain the huge range of phenomena that are "partly alive". And then wonder how come we have the gap. The belief in God or the supernatural comes entirely from this perceived gap. Only God (means no one except by miracle) can bridge this gap.