When introducing this basic grid in my previous post I made the off-hand statement that "proximity is 9/10ths of a relationship". This is something I remember hearing at one time and it has stayed with me. In 1997 Robert Axelrod published his now famous model of cultural dissemination using cellular automata. The model gives computational and theoretical basis for studying the emergence of culture through the interactions between individuals. With simple rules the model enables study of the effect of individuals having similar traits becoming more similar, as well as the possible counter effect in which tendency toward local similarity leads to global polarization.

Believe it or not: The grid below is a graph. What is a graph? A graph is a set of nodes, or vertices, that are connected by paths, also called edges. The term "edge" in a grid is particularly salient as each cell ajoins each of its neighbors along its edges. The path from one node, or cell, to its neighbor is at its edge. If you draw your cursor across the grid below you will freely follow paths sequentially connecting nodes which are jam-packed like eggs in a carton, tiles in a mosaic, atoms in a crystal, or people in a packed subway car.

In this third and final post about the principles of natural selection introduced in Chapter 1 of Enrico Coen's Cells to Civilizations, The Principles of Change That Shape Life I include treatment of the fourth principle, reinforcement. A variant feature of marbledom—the color orange—is given an arbitrary 66 to 34 selection advantage during cycles of persistence (i.e. reproduction). Although this advantage builds upon itself through successive generations, an interesting phenomenon occurs, as pointed out by Coen. As the advantaged orange marbles approach saturation in the population, their rate of increase slows. Coen represents this by the prototypical 'S' curve where the rate of convergence is limited by there being fewer blue marbles to select and eliminate.

We enter, we update, we exit (with object constancy).

In Part 1 of this series I used a stacked bar chart to visualize my interpretation of the population drift algorithm described by Enrico Coen in the first chapter of his book Cells to Civilizations, The Principles of Change That Shape Life. See that post for an overview of the four main principles Coen explains are at play in evolution (variation, competition, persistence, reinforcement). Here I have used what in D3js is called packed circles, or bubble chart, to render a more figurative, real-time version of the algorithm (Note: may take up to 5 or more minutes to complete).

Inspired by reading the first chapter in Enrico Coen's Cells to Civilizations, The Principles of Change That Shape Life, I decided to code and visualize my interpretation of the algorithm he describes for using two colors of marble to demonstrate population drift.