The Evolution of Invertebrates

Genome of vertebrates underwent a duplication sometimes in the cambrian period, before evolution split the jawless and jawed fishes. Two jawed fishes hybridized later and underwent a second duplication of their genomes. This hybrid went on to become the ancestor of all bony fish. Some of the linked blocks of gens also seem to be present in the genomes of certain unicellular creatures like coena flagelates. Those are the closest relatives of multi cellular animals.