If you are following Cortex Project, I guess you must be interested in AI, robotic and maybe artificial life. Then you may have come across writings about life definition. Since I became an AI passionate, I came across many. These writings always end up giving a list of criteria that a thing has to meet to be called alive.
But these lists always let me unsatisfied.
Common life definition
The Wikipedia article about "life" ends up giving the following list:
- Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.
- Organization: Being structurally composed of one or more cells, which are the basic units of life.
- Metabolism: Transformation of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
- Growth: Maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
- Adaptation: The ability to change over a period of time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity as well as the composition of metabolized substances, and external factors present.
- Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun (phototropism) and by chemotaxis.
- Reproduction: The ability to produce new individual organisms, either asexually from a single parent organism, or sexually from two parent organisms.
This list is more or less focused on biologic life, includes many criteria, some of them being redundant. Let's try to generalize it and use the simplest concepts and words we can think of.
The way I understand homeostasis and organization is that a living entity must have a physical body that is different from the outside environment, organized and somehow stable compared to this environment.
Metabolism. It think this is one of the most important criterion. I would put it in a very simple way: life uses energy. The source of energy is found in the environment. By the way, that's where life is far ahead from robotic. Every living thing on this planet is an incredible energy plant.
Let's skip to the 6th criterion which is a very important criterion in my opinion: response to stimuli. I would say that life must somehow sense its environment and react to what it senses.
Now, the list also includes three other criteria I disagree with. They are growth and the capacities of reproduction and evolution (which is behind adaptation).
In my opinion, these three criteria actually hide the true and main caracteristic of life. The main caracteristic of life is to do whatever it takes to keep on living.
Reproduction and evolution are just the way life on Earth has managed to do it. And growth is simply a consequence of reproduction and evolution. Said differently, biologic life found that the best way to perpetuate life is through reproduction and evolution. Reproduction and evolution is not intrinsically required but perpetuating life is because otherwise life would be a transient accident and there would be nobody to wonder about life definition.
So, what would my own list look like?
It finally all comes down to four simple criteria, expressed as follows:
A living entity shall:
- Have a body. A physical interface that separate the entity from the environment. The body has a different organization and development than the environment.
- Use energy and/or matter found in the environment, and the environment only (complete autonomy). The life form transforms energy and/or matter from the environment into different form of energy and/or matter.
- Sense its environment and its internal state and react to this information.
- Perpetuate life endlessly (assuming the environment does not change). This can be achieved by never dying (constantly repairing the body) and/or giving birth to new life.
Note that this definition includes all living form on Earth except viruses that can be considered as mechanical replicators. I would argue that when contaminating a cell, the virus loses its body. Moreover, the virus does not use energy or matter, it's the contaminated cell that does.
Is robotic life feasible ?
Now that we have this definition, we can wonder if creating robotic life is possible.
Criteria 1 and 3 are easily met.
The second criterion is very hard to meet as soon as photovoltaic energy is not an option. Photovoltaic energy makes the robot equivalent to plants energy-wise which is very limiting.
Recently, I came across a robot using the energy of waves to travel across the oceans. This is a good exemple of a robot that meets this criterion.
Though feasible in theory, the fourth criterion is obviously the main obstacle to robotic life. I will not elaborate on the subject here as it is too vast to be covered in this post.
So, the answer to the question is yes, but it is a real challenge.
Fortunately, enthusiasts can create artificial environments where these criteria are easier to meet and experiment with artificial life.
