A review of vestigial claims of the human spleen reports no clear evidence for its function until the late 1950s. It is now acknowledged to be a critical organ serving at least six different important functions. Furthermore, the spleen exists universally in jawed vertebrates and is not found in any invertebrates, so it has no evolutionary history. The lack of evidence for simpler or transitional forms of the spleen supports the conclusion that jawed vertebrates have always had fully functional spleens that are perfectly designed for their needs.