First, there is speciation (species-splitting or cladogenesis), caused by geographical isolation or some other mechanism. 首先，因地理隔离或其它一些机制导致物种形成（物种分裂或系枝进化）。
Cook seems to have been the first to coin the term \'speciation\' for the splitting of lineages or \'cladogenesis,\' as opposed to \'anagenesis\' or \'phyletic evolution\' occurring within lineages. 这一术语与发生在世系内的“前进演化”或“种族的进化”这些提法相抵触。
