In this article, I model both the uniparental teaching hypothesis and the disparate benefits hypothesis as processes of gene-culture coevolution Boyd and Richerson ; Richerson and Boyd where beneficial cultural traits are transmitted uniparentally. In teaching, as opposed to purely observational learning, the teacher modifies its behavior to better transmit information to the target. Selection should, therefore, drive mothers to preferentially teach daughters over sons. To assess each model, I determined how well it explains the 3 observed patterns of sponging frequency in the dolphins of Shark Bay: However sponging occurs in at least 2 maternal lines, one in each of 2 populations in Shark Bay, suggesting either separate inventions or a case of horizontal transmission between migrants from one population to another. This behavioral modification is often costly for the teacher and, therefore, may have negative direct fitness consequences Caro and Hauser and can be considered a form of altruism Thornton and Raihani Sons do not transmit cultural traits because they do not raise their offspring. THE MODELS To find out whether the uniparental teaching hypothesis better explains patterns of sex-biased transmission than the disparate benefits hypothesis, I constructed a numerical simulation of each hypothesis. The hypothesis I develop in the article suggests that the population-level patterns of sponging in bottlenose dolphins are the result of teaching in a species with uniparental care. Sex-biased transmission occurs, according to the disparate benefits hypothesis, not because mothers preferentially teach daughters, but because daughters spend more effort than sons learning from their mothers. The reason for sex-biased transmission is a puzzle because many of the transmitted behaviors would be beneficial to both sexes. The former mechanism seems important in maintaining sponging behaviors in the Shark Bay dolphin population Kopps and Sherwin as it seems to be transmitted primarily from mothers to offspring. For example, in just 2 populations in Shark Bay, Australia, dolphins employ at least 13 foraging behaviors that seem to be culturally transmitted primarily from mothers to offspring, often with a bias toward daughters Mann and Sargeant An unsolved puzzle is why sponging is transmitted at much higher frequencies from mothers to daughters than from mothers to sons. Teaching a son gives him a reproductive benefit for one generation.