Start with 2 orthogonal attributes and a population of individuals. There is a 'previous' generation (the parents at generation i), and a 'next' generation (the children at generation i+1). The generations are displayed side by side, with parents on the left. There is one dot per individual, placed according to attributes.
The simplest model is where each parent has a single child with equivalent attributes. In a sense, each individual in the parent generation is copied exactly into a single individual in the child generation.
To model evolution we explore variations in the mechanism that 'copies' parents to children.