Posted by: zyxo | April 28, 2008

What is life ?


MitosisImage via Wikipedia

Do you feel alive ?
So tell me, what is it ?

Is a plant alive ?
Is a bacterium alive ?

Is a virus alive ?
Is a prion alive ?

Is a flame alive ?
Is a waterfall alive ?

When I was a lot younger, I somewhere read, or was told that “alive” means : has the ability to reproduce itself. At that time, it seemed very logical. Plants and animals, even bacteria, do reproduce themselves.

At that time.

Recently I began to see things from another angle.

Scientific facts can be tested. So let us do the test. Take a box, put a plant in it and let us come back let’s say in a month. I reckon the plant will be dead and produced no offspring. Idem with a little bird in the box. Idem with about anything … alive.

Conclusion : “alive” does not mean “can reproduce itself”.

What is missing. Fairly obvious : food, light, water, another animal of the opposite sex, the right environment, and so on. So who is reproducing who ? Or what is reproducing who, or what ?

If it is the environment with everything in it that reproduces the living things, what makes those things living ? The environment (re-)produces a lot of things : snowflakes, flames, patterns in a waterfall, … are these things alive ? Why not ?

In an earlier post I wrote about evolution and (re-)production. Evolution did not start when life started, but with the big bang (or earlier ?). Everything evolved, and the most successful structures took over time after time. Now these successful structures are called bacteria, humans, insects …

In the course of this evolution we can observe a few paradigm shifts :

First episode : sort of random production of new structures, no ressemblance whatsoever with the original structures. Example : a mountain transforms in a pile of debris by means of erosion. A bit of non-randomness can be observed also : forming of snowflakes, of cristals as a result of some physical properties.

Second episode : copying of old structures. The structures that are most easily copied were the fittest. Here I think of the ancient soup a solution of among others more or less large organic molecules where random production but also some copying was going on.

Third episode : copying of old structures, not based on the structure itself, but on some other structure containing the necessary information, the plan. This means that the structures of the first level from the second episode had evolved and created a second-level structure that facilitated the copying of the first-level structure. So in the third episode the first-level structures had began to shape their environment.

Fourth episode : idem as third episode, but here, the second-level structure had become complex enough to further shape parts of the environment that were not parts of the first- or second-level structure. Hole-digging, nest-building, house-building … A third-level structure building was going on. You see: no plants do that, just animals. (or do I miss something or, some weird examples ?)

Fifth episode : Second-level structures pass information to one another that is not part of the structure : ants leave pheromone trails, bees dance, birds sing, people write blogs. Memes are born. They are not structures, but another sort of information units that follow the survival-of-the-fittest-rules where the most successful continue to be reproduced.

Sixth episode : Groups of second-level structures use memes to co-operate in order to create third-level structures of such a complexity that these third-level structures are able to copy themselves and eventually evolve. It is the episode of artificial intelligence with for example robots creating even more intelligent robots. As you know, this episode has yet to start.

This history is described rather roughly, but I think you see the line of it.

So what is life ? I think it started in the third episode, with the two-level structures. And where does it end ?

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