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Local Competition.

One of the problems that has been observed with the process of evolution in Tierra is that it suffers from premature convergence due to global interactions between cells [Adami & Brown 94].

Chris Adami and Titus Brown sought to overcome this problem in their Avida system by giving each of the cells a location on a two dimensional toroidal grid. Cells can only interact with other cells occupying nearby grid positions, thereby slowing down the rate of propagation of evolutionary changes throughout the total population and promoting heterogeneity.

Cosmos addresses this problem by placing organisms on a grid (as in Avida), and by restricting cells to only be able to communicate and interact with other cells within a certain distance on the grid (but see the further discussion on this topic in Section 7.2.3).

Tim Taylor