Understanding how organs originate is challenging due to the twin problems of explaining how new cell types evolve and how collective interactions between cell types arise and become selectively advantageous. Animals are assemblages of organs and cell types of different antiquities, and among the most rapidly and convergently evolving are exocrine glands and their constituent secretory cell types. Such structures have arisen independently thousands of times across the Metazoa, impacting how animals chemically interact with their environments. The recurrent evolution of exocrine systems provides a paradigm for examining how qualitative phenotypic novelties arise from variation at the cellular level. Here, we take a hierarchical perspective, focusing on the evolutionary assembly of novel biosynthetic pathways and secretory cell types, and how both selection and non-adaptive molecular processes may combine to build the complex, modular architectures of many animal glands.

由于解释新细胞类型如何进化以及细胞类型之间的集体相互作用如何出现并成为选择性有利的双重问题，因此了解器官如何起源具有挑战性。动物是不同古代器官和细胞类型的集合，其中最快速和趋同进化的是外分泌腺及其组成的分泌细胞类型。这种结构在后生动物中独立出现了数千次，影响了动物与环境的化学相互作用。外分泌系统的反复进化提供了一个范式，用于研究定性表型新奇是如何从细胞水平的变化中产生的。在这里，我们采用分层的视角，专注于新的生物合成途径和分泌细胞类型的进化组装，