Hypotheses of feeding are intimately bound up with scientific accounts of the early evolutionary history of vertebrates. The origin of vertebrates, for example, has been linked to and ecological shift from suspension feeding to active predation, and changes in feeding mechanism are also invoked in various scenarios that seek to explain the origin of gnathostomes (vertebrates with jaws) from among the agnathans (jawless vertebrates)(see references in Purnell 1995). What is probably the most widely held hypothesis explaining the decline of agnathans and the rise of jawed vertebrates invokes competition for food resources as a major factor (see, e.g. Pough et al. 1996). Changes in feeding mechanisms are central to explanations of diversification in more advanced gnathostome fish, and the same may have been true of the earlier diversification of the agnathans.

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