  We consider the following problem: from a given set of gene families trees on
a set of genomes, find a first speciation, that splits these genomes into two
subsets, that minimizes the number of gene duplications that happened before
this speciation. We call this problem the Minimum Duplication Bipartition
Problem. Using a generalization of the Minimum Edge-Cut Problem, known as
Submodular Function Minimization, we propose a polynomial time and space
3-approximation algorithm for the Minimum Duplication Bipartition Problem.
