Modern cultural evolution theory adopts a variety of concepts and methods developed in mathematical biology, in particular population genetics theory. In addition to forward-looking approaches such as two-locus models, backward-looking approaches such as coalescent theory, which describe ancestral states of the current population, have played an important role in population genetics. Here, we show how forward and backward approaches can be applied to two examples in cultural evolution. The first example deals with the number of cultural traits, which can be analyzed by a backward approach. Cultural coalescent theory illustrates many unique aspects of cultural processes such as information transfer (i.e., social learning) from many donors (“cultural parents”), including or excluding the biological parents. Theory predicts that many cultural traits of intermediate (or higher) frequency (popularity) can exist that are surprisingly old. Many unsolved issues remain, however, such as how to incorporate social structure as well as natural and/or cultural selection, which we believe to be an urgent agenda. The second example is the punishment of sibling incest, a problem to which cultural coalescent theory cannot currently be usefully applied. By analyzing forward recursions, we show that punishment is ineffective in suppressing incest, unless the incestuous inclination is diminished by the presence of punishers. Based on these examples, we discuss the merits and demerits of forward and backward approaches.

中文翻译：

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文化进化过程的正向和反向建模


现代文化进化论采用了数学生物学中发展的各种概念和方法，特别是群体遗传学理论。除了双位点模型等前瞻性方法外，描述当前种群祖先状态的合并理论等后向性方法在种群遗传学中也发挥了重要作用。在这里，我们展示了如何将前向和后向方法应用于文化进化中的两个例子。第一个例子涉及文化特征的数量，可以通过向后的方法进行分析。文化融合理论说明了文化过程的许多独特方面，例如来自许多捐助者（“文化父母”）的信息传递（即社会学习），包括或排除亲生父母。理论预测，可能存在许多中等（或更高）频率（流行度）的文化特征，这些特征出奇地古老。然而，许多未解决的问题仍然存在，例如如何整合社会结构以及自然和/或文化选择，我们认为这是一个紧迫的议程。第二个例子是对兄弟姐妹的惩罚，这是一个文化融合理论目前无法有效应用的问题。通过分析前向递归，我们表明惩罚在抑制方面是无效的，除非的倾向因惩罚者的存在而减少。基于这些示例，我们讨论了前向和后向方法的优缺点。