The line between life and not life.

Historically there has been a huge between what people consider to be non-living system, on the one side and living system on the other side. Over the last hundred and 50 years or so, science has kind of blurred this distinction between non-living and living systems. For example, a virus is a natural system, but it doesn’t satisfy all the requirements and characteristics of living system. Here is characteristics of living system:

1. Life has a body. It is necessary to distinguish the self from the environment.

2. Life has metabolism. It is a process by which life can convert resources into building blocks so it can maintain and build itself.

3. Life also has a kind of inheritable information.

If we couple the first two – the body and the metabolism – we can come up with the system that could perhaps move and replicate, and if we coupled it with the inheritable information, we can come up with the system that would be more lifelike and would perhaps to evolve.

So in the lab scientists use a model system – protocell. It’s a simple chemical model of a living cell. They start simple, they make some structure that have some characteristics of living system. They the idea of self-assembly. What that mean is they can mix some chemicals together and this chemicals will start to self-associate to form larger structure.

What about the other aspects of living systems?  They started with a natural occurring clay called montmorillonite. It could run a metabolism on it.  Certain kind of molecules like to associate with the clay. 

As we heard earlier, movement is very important in these kinds of living systems. It is moving around, exploring its environment, and remodeling its environment, by these chemical waves that are forming by the protocell.  So I add some food source to the system. The protocell moves. It encounters the food.  If we count the number of chemicals in that system, actually, including the water that's in the dish, we have five chemicals that can do this. If we put these protocells together we’ll see that two moving protocells like to circle the each other, and they form the kind of dance. 2 different kind: protocell A starts to vibrate around, just dancing. Protocell B all come together and fuse into one big one.

They fuse together and the one protocell just dance around. This happens until all of the energy is basically used up and than game over. After a bunch of repeats of this experiments prA and prB fused together to form hybrid prAB.

We are able to then see the self-assembly of oil droplet bodies and the black spots inside this kind of black tar. We put them into one of this experiments. They appear to have the some kind of behavior where they kind of circle around of each other and follow each other but it working with just primordial conditions. If we add some sources, they became very energetic and able to find resources in the environment.

 If we went to another planet and we thought there might be life there, how could we even recognize it as life? Well, they came up with three very general criteria. First is -- and they're listed here. The first is, the system has to be in non-equilibrium. That means the system cannot be dead,  Basically what that means is, you have an input of energy into the system that life can use and exploit to maintain itself.  this is important because life transforms resources from the environment into building blocks so it can maintain itself.  So by making these chemical, artificial life experiments, we hope not only to understand something fundamentalabout the origin of life and the existence of life on this planet, but also what possible life there could be out there in the universe.