CONSERVATION AND COMPLEXITY. “During the last nine years, homologues of genes involved in the regulation of programmed cell death in Caenorhabditis elegans have been identified in sponge, in Hydra vulgaris, in the fruitfly Drosophila melanogaster, in zebrafish, in mice and in humans. As frequently occurs during evolution, however, this striking conservation in both sequences and functional properties has been associated with a great level of diversification.”
http://www.nature.com/cdd/journal/v9/n4/full/4400950a.html