The evolutionary origin of flowers has long been a famous puzzle. The problem has not been solved, but there have been advances. The Anthophyte theory was based on relationships inferred in the first cladistic analyses of seed plants done in the mid-1980s. Support for these relationships vanished when molecular phylogenetic analyses gave strong evidence that living gymnosperms are monophyletic, contradicting the anthophyte relationships. Paleobotanical cladistic analyses continue to find the anthophyte relationships (although sometimes weakly); some paleobotanists accept the molecular phylogenies but others do not. The Mostly Male theory arose from the study of the evolution of development, based on multiple sources of data. It provides a detailed scenario for flower origins, suggesting that the flower arose mostly from the male reproductive structure of the gymnosperm ancestor, and that the ovule precursors moved ectopically onto this formerly male structure. Some new data favor this theory while other data oppose it. The fossil group Corystospermales, which fits the theory well, may not figure as potential ancestors, but the Caytoniales may fill the same role. Other theories based on the evolution of development have been advanced to explain flower origins. Friedman's modular theory accounts for the angiosperm embryo sac and triploid endosperm. This paper is Floral Genome Project contribution number 56.