74 ◾ Biological Computation
organisms that are very similar or even identical to themselves. Recall that
von Neumann’s purpose when inventing the CA model (together with the
famous mathematician Stanislaw Ulam) was to investigate the phenom-
enon of self-replication.
It is easy to nd CA that exhibit what looks like self-replication. For
instance, a 1-D cellular automaton where a cell with value 1 causes the
cells in its neighborhood to also change their values to 1. But this is not an
interesting example of self-replication since copying the value 1 from cell
to cell is very dierent from the complex processes of self-replication in
the living world which we are trying to investigate, such as cell division, or
the creation of a human bab ...