Descent with modification is the foundational framework of all of evolution. Yet evolutionary novelties are defined as lacking affinities to structures that already existed in the ancestral state, i.e. to somehow emerge in the absence of homology. We posit that reconciling both perspectives necessitates the existence of a type of innovation gradient that allows descent with modification to seed the initiation of a novel trait, which once in existence can then diversify into its variant forms. Recent work on diverse, textbook examples of morphological novelties illustrate the value of the innovation gradient concept. Innovations as profound and diverse as insect wings, beetle horns, and treehopper helmets derive from homologous source tissues instructed in their development by homologous gene regulatory networks. Yet rather than rendering these traits no longer novel, we posit that discoveries such as these call for a reassessment of the usefulness of defining evolutionary novelty as necessitating the absence of homology. Instead, we need to redirect our attention to how ancestral homologies scaffold and bias the innovation gradient to facilitate hotspots of innovation in some places, and deep conservation elsewhere.

中文翻译：

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从改良的血统到新颖的起源

带有修改的下降是所有进化的基础框架。然而，进化新奇被定义为对祖先状态中已经存在的结构缺乏亲和力，即在没有同源性的情况下以某种方式出现。我们假设调和这两种观点需要一种创新梯度的存在，这种梯度允许通过修改的下降来启动新特征的种子，一旦存在，该特征就可以多样化为其变体形式。最近关于形态新颖性的各种教科书示例的工作说明了创新梯度概念的价值。昆虫翅膀、甲虫角和树蝉头盔等深刻而多样的创新源自同源源组织，它们在发育过程中受到同源基因调控网络的指导。然而，我们并没有使这些特征不再新颖，而是假设诸如此类的发现需要重新评估将进化新颖性定义为需要缺乏同源性的有用性。相反，我们需要将注意力转移到祖先同源性如何支撑和偏向创新梯度，以促进某些地方的创新热点和其他地方的深度保护。