Uroboros,  the Serpent biting its own tail appears in New Kingdom Egypt (1600 years b.c.e.). It was taken up by the Phonecians and then to the Greeks, who called it the Ouroboros (or  uroboros), which means tail-devouror. (http://www.kheper.net/topics/archetypes/uroboros.htm )

The image is taken from a 15^th century Greek alchemical text. (http://abacus.best.vwh.net/oro/oro3.gif ). Here it symbolizes the eternity of life.

The CA is controlled by the following buttons:
Replant-No replant: Is a toggle switch which triggers or stops zygote planting. 
Shorter:  Makes CA shorter
Longer: Makes CA longer 
Obstacle a toggle switch which places an obstacle at x=15.
Move obstacle+ moves it downward.
Move obstacle- moves it upward.
Kill CA

Upon loading the applet a zygote is planted, and  differentiates into a mature CA. Let it evolve until it matures into an Uroboros, which hunts its own tail. Only the first CA state (state-0) is active, all other states are memory states. State-0 is a stem state (cell) which lives forever. The rest are short lived  transitional states (cells) or memory states which store the past events of the stem state. Their maximal age is 58 time units where upon they die.

As the Uroboros advances, its stem cell enters the space vacated by the last dying memory state. The CA maintains a steady state in which death rate equals the birth rate.  During each time step the stem  cell generates two daughter cells: One replaces the parent and becomes a stem cell. The other becomes a transitional cell which starts advancing backward toward its graveyard (the white space between head and tail). This is known as asymmetrical cell division.

Clicking  on  “kill CA” kills the stem cell whereupon no new cells are formed. Death rate > (birth rate = 0) and the Uroboros . shortens. If you click “replant” a new zygote is formed. After clicking “kill CA” and “no replant” the Uroborus vanishes. Uroborus fate depends on two buttons:
“kill CA” and “no replant” Uroborus vanishes.
“kill CA” and “    replant”  A new zygote is planted.

Evolution

Click on “replant”, activate the “obstacle” and let the stem cell interact with it. The Uroboros will be perturbed and its structure changes. If  it dies it will be replaced by a new zygote  regaining its original structure.  It may however evolve into a new steady state structure (solution)

Asymmetrical cell division is a fundamental property of life

The applet illustrates that life is maintained by an asymmetrical division of a stem cell which generates a short lived progeny. The human being originates from a zygote which divides asymmetrically. One of its progeny matures into a short lived adult. The other is called a gamete, which is  destined to propagate life and accounts for the fact that life is eternal.

Parthenogenesis

Generally two gametes, the ovum and sperm, have to unite in order to form a zygote. However a zygote may be generated also only by the female gamete. This process is called parthogenesis. The uroboros zygote is generated by pathenogenesis.

Three theories explain how life started on earth:
1. It was created. (Genesis)
2. It evolved from an-organic matter.
3. It reached earth from outer space (Panspermia)

Additional reading
Complexity
Streaming tissues