Cockroaches scurry around with thousands of pieces of bacterial genomes

Last week, we looked at a new study of the origin of complex cells , one that showed that our ancestors' genomes were pieced together from bits and pieces of multiple species. It put a spotlight on a phenomenon called horizontal gene transfer, in which a gene from one species is incorporated into the genome of a distantly related species. The frequency of horizontal gene transfer means that, in addition to the neatly branching trees that relate species by common descent, there are small threads