“Such “pyrrhic victories” are of course ubiquitous in the development of U.S. tax law, leading the late Justice Robert H. Jackson to quip that tax is “a field beset with invisible boomerangs.” Arrowsmith v. Commissioner, 344 U.S. 6, 12 (1954) (Jackson, dissenting). See Kirk J. Stark, The Unfulfilled Tax Legacy of Justice Robert H. Jackson, 54 Tax L. Rev. 171, 251-256 (2001). To carry the evolutionary story further, one might observe that the development of the tax law is sometimes characterized by a process similar to evolutionary phenomenon of “antagonistic pleiotropy,” a condition where a single gene influences more than one trait—one with beneficial effects and the other with harmful effects. In a similar way, a single legal rule will often have pro-taxpayer and pro-government effects, depending on the class of taxpayer. Thus, in the same way that a gene selected for some beneficial trait might carry with it some other harmful trait, government efforts through litigation to push the development of a legal rule (e.g., the scope of the “realization” doctrine) in one direction with respect to one class of taxpayers (e.g., taxpayers with gains) will sometimes have the opposite effect on another class of taxpayers (e.g., taxpayers with losses). A fuller “evolutionary” theory of the development of U.S. tax law might seek to account for such phenomena.”