  Persistence phenomena in colonization processes could explain the negative
results of SETI search preserving the possibility of a galactic civilization.
However, persistence phenomena also indicates that search of technological
civilizations in stars in the neighbourhood of Sun is a misdirected SETI
strategy. This last conclusion is also suggested by a weaker form of the Fermi
paradox. A simple model of a branching colonization which includes emergence,
decay and branching of civilizations is proposed. The model could also be used
in the context of ant nests diffusion.
