In this seminar I will present an analysis recently implemented in my group to investigate the origin of species. By studying three-node network motifs of metabolic pathways, we discovered that differences between some biological species are reflected by the distribution of the network motifs. We find that cellular organelles display motif distributions that are distinct from one another and likely reflect their distinct functional roles in the cell. We apply the methodology of motif mining and analysis to investigate the origins of Eukaryotic organelle evolution. We find novel evidence suggesting that an alpha-proteobacterium may not have been the ancestor of modern mitochondria. As far as we know, this is the first attempt to use metabolic network motifs to investigate the evolution of species.