DrJay writes "Hot on the heels of Slashdot's coverage of a controversial model for a viral origin of the multi-cellular branch of life, Nature has published an alternative model that has nothing to do with viruses. Ars Technica's science journal has the rundown on the differences between these proposals." From the Ars article: "It's funny that this proposal for the origin of Eukaryotes should hit the popular press at a time where Nature has just published a hypothesis regarding the formation of the nucleus that has nothing to do with viruses, but everything to do with parasites. The parasites in this case are molecular: Type-II introns. These DNA sequences exist in both eukaryotes and bacteria, where they can insert in the middle of genes without causing harm because they can undergo chemical reactions by which they remove themselves from the RNA messages the genes make."