Department of Mathematical Sciences Based on Modeling and Analysis, School of Interdisciplinary Mathematical Sciences, Meiji University, Nakano, Tokyo 164-8525, Japan.
Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
Proc Natl Acad Sci U S A. 2024 Nov 26;121(48):e2322880121. doi: 10.1073/pnas.2322880121. Epub 2024 Nov 18.
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.
现代文化进化理论采用了数学生物学中发展起来的各种概念和方法，特别是群体遗传学理论。除了两基因座模型等前瞻性方法外，描述当前群体祖先状态的回溯方法，如合并理论，在群体遗传学中也发挥了重要作用。在这里，我们展示了如何将前瞻性和回溯性方法应用于文化进化的两个例子。第一个例子涉及文化特征的数量，可以通过回溯方法进行分析。文化合并理论说明了文化过程的许多独特方面，例如从许多供体（“文化父母”）传递信息（即社会学习），包括或不包括生物父母。理论预测，许多中间（或更高）频率（流行度）的文化特征可以存在，而且非常古老。然而，仍有许多悬而未决的问题，例如如何将社会结构以及自然和/或文化选择纳入其中，我们认为这是一个紧迫的议程。第二个例子是兄弟姐妹乱伦的惩罚，文化合并理论目前无法有效地应用于这个问题。通过分析正向递归，我们表明，除非惩罚者的存在减少了乱伦的倾向，否则惩罚在抑制乱伦方面是无效的。基于这些例子，我们讨论了前瞻性和回溯性方法的优缺点。
