The various species of salmon have many names, and varying behaviors.
Eosalmo driftwoodensis, the oldest known salmon fossil in the fossil record, helps scientists figure how the different species of salmon diverged from a common ancestor. The British Columbia salmon fossil provides evidence that the divergence between Pacific and Atlantic salmon had not yet occurred 40 million years ago. Both the fossil record and analysis of mitochondrial DNA suggest that the divergence occurred by 10 to 20 million years ago. This independent evidence from DNA analysis and the fossil record reject the glacial theory of salmon divergence.