CellLife

The rules couldn't be simpler:

• red cells eat green and pink cells, otherwise cells bounce off each other
• when a creature loses its pink cell it dies

While that's running, have a read below.

Source:

• CellLife.java - The main applet source file, stores a list of tjhCreature's.
• tjhCreature.java - This class manages the properties of a creature, stores a singe tjhCell - the root cell.
• tjhCell.java - This class manages the properties of a single cell. Each cell has a list of sub-cells, creating a tree structure.
• tjhGene.java - The genome representation of the design of a creature. Each gene contains the type of the cell it represents. This is another tree structure, mirroring the physical aspect of the creature (its phenotype).
• tjhNeuron.java - Each cell can respond to nearby cells by moving in some way, this is a model of a simple neuron.
• tjh2dVector.java - A utility class that manages a 2D location or vector.
• tjhBucket.java - The structure for each square in our space-partitioning system, stores a flag saying whether the square has a cell in it and a reference to the cell if there is one.
• tjhBuckets.java - The time-saving space-partitioning class that detects collisions between cells.

Have a look at the code documentation (generated by javadoc) - see, it's not difficult is it?

To use the source code:

1. Copy the above files and this html file (index.html).
2. Download Sun's Java Development Kit (http://java.sun.com/products)
3. Compile with the command: javac *.java.
4. Load index.html into a java-supporting browser and enjoy.

Some simple things to change to get you started:

• Change MAX_CREATURES in CellLife.java to put more creatures into the world.
• Change RADIUS in tjhCell.java to make the cells bigger or smaller.
• Change P_PHYSICAL_MUTATION in tjhGene.java to make physical mutations happen more or less often.

Background:

• Primordial Life - Colourful 2D biots take over the internet.
• Framsticks - A physical 3D simulation of stick-creatures that try to walk and swim.

None of the simulations I have seen even approach the sheer creativity of evolution. There are several reasons for this, firstly that by its nature evolution requires large populations and lots of time to work. More interestingly, for an evolution simulation to really take off you need the right representation not only to allow the creatures enough flexibility to create successful forms but also with the right pressures to drive the survival of those creatures that are more successful in interesting ways.

This simulation is an attempt to get at that representation. At the moment all it shows is potential. It was thoroughly inspired by the Primordial Life project but addresses two perceived issues:

• it is in open-source Java on the web so everyone can play with it and explore the possibilities.
• it uses a tree-structure of cells to allow large modular creatures with interacting limbs.

• more intelligent control of cell movement
• more inputs to each cell (eg. communication between cells, current orientation of parent)
• creature itself should be able to control its gross movement, not just drift

• Reproduction occurs only when two creatures bump their pink bits against each other (or population is really small). Thanks to David Evans (see below) for this suggestion.

Details:

In an attempt to keep things simple, there are just two types of cell: red and green. (Pink ones behave like greens, they are just drawn differently.) The pink cells (the roots of the tree structure) are like the 'heart' of the creature - the creature must protect its pink cell from attack else die. Green cells are intended to be like passive energy collectors (plant similarities) but are currently useless and rapidly get selected out. Red cells are intended to be the active attackers, gathering food by eating the green cells of other creatures and improving reproduction chances by killing other creatures.

The creatures are made up of a tree of cells extending outwards from the root cell. The branches of the tree move about at random unless the creatures control this movement themselves by rotating themselves either clockwise or anticlockwise around their parent.

The intention is that creatures will respond to their environment by moving into a set position or in a set manner, allowing them to adopt various positions (defensive, attacking, searching, etc.) depending on their mood.

The current implementation of the creatures' brains gives each of them a single neuron. With the orientation defined by the cell's parent being 'behind' it, the cells responds to the presence of enemy cells to its left or right. The neuron determines how the cells responds, if at all.

Sensory inputs: green_left, green_right, red_left, red_right

Possible outputs: rotate_left, rotate_right, no response

Edited highlights of the Primordial Life mailing list:

What I thought might make an interesting evolutionary trade-off is to base the reproduction on an explicit sexual pairing. I'm assuming that at the moment when a biot dies, you replace it by spawning a new one based on the genome of a randomly selected survivor in the pool. How about if we created a new biot whenever the pink cells of two biots touched (at the moment this relatively rare encounter does nothing but bounce.) Ideally, the newborn would use a crossover-generated genome from both parents, but it could also be randomly chosen from one or the other.

In a blind, hard-wired world I would expect to see some species that flaunt their pink bits (they would lead short, but promiscuous lives) and others that are more demure (leading long, boring lives.)

With vision and brains in gear, it should lead to interesting behaviour, like defensive positions that open up into mating positions.

I realise that with the recent talk of wiring and brain boxes, that the pink cell might be considered by some to be the brain, rather than the genitals. I have, however, come across many life forms (mostly in middle-management) where the two functions seem to have merged in the same organ.

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