Department of Anatomy, Howard University College of Medicine, Washington, DC 20059, U.S.A.
Biol Rev Camb Philos Soc. 2015 May;90(2):502-21. doi: 10.1111/brv.12121. Epub 2014 Jun 11.
The notion of scala naturae dates back to thinkers such as Aristotle, who placed plants below animals and ranked the latter along a graded scale of complexity from 'lower' to 'higher' animals, such as humans. In the last decades, evolutionary biologists have tended to move from one extreme (i.e. the idea of scala naturae or the existence of a general evolutionary trend in complexity from 'lower' to "higher" taxa, with Homo sapiens as the end stage) to the other, opposite, extreme (i.e. to avoid using terms such as 'phylogenetically basal' and 'anatomically plesiomorphic' taxa, which are seen as the undesired vestige of old teleological theories). The latter view tries to avoid any possible connotations with the original anthropocentric idea of a scala naturae crowned by man and, in that sense, it can be regarded as a more politically correct view. In the past years and months there has been renewed interest in these topics, which have been discussed in various papers and monographs that tend to subscribe, in general, to the points defended in the more politically correct view. Importantly, most evolutionary and phylogenetic studies of tetrapods and other vertebrates, and therefore most discussions on the scala naturae and related issues have been based on hard tissue and, more recently, on molecular data. Here we provide the first discussion of these topics based on a comparative myological study of all the major vertebrate clades and of myological cladistic and Bayesian phylogenetic analyses of bony fish and tetrapods, including Primates. We specifically (i) contradict the notions of a scala naturae or evolutionary progressive trends leading to more complexity in 'higher' animals and culminating in Homo sapiens, and (ii) stress that the refutation of these old notions does not necessarily mean that one should not keep using the terms 'phylogenetically basal' and particularly 'anatomically plesiomorphic' to refer to groups such as the urodeles within the Tetrapoda, or the strepsirrhines and lemurs within the Primates, for instance. This review will contribute to improving our understanding of these broad evolutionary issues and of the evolution of the vertebrate Bauplans, and hopefully will stimulate future phylogenetic, evolutionary and developmental studies of these clades.
自然层级的概念可以追溯到亚里士多德等思想家，他们将植物置于动物之下，并根据复杂程度将后者从“低级”动物到“高级”动物（如人类）进行分级排列。在过去的几十年里，进化生物学家倾向于从一个极端（即自然层级的概念或从“低级”到“高级”分类单元的复杂性的一般进化趋势的存在，智人是最终阶段）转变为另一个相反的极端（即避免使用“系统发育基础”和“解剖学原始”等术语，这些术语被视为旧目的论理论的不必要残余）。后一种观点试图避免与自然层级的原始人类中心主义观念任何可能的内涵，从这个意义上说，它可以被视为一种更符合政治正确的观点。在过去的几年和几个月里，人们对这些主题重新产生了兴趣，这些主题在各种论文和专论中进行了讨论，这些论文和专论通常支持更符合政治正确观点的观点。重要的是，大多数四足动物和其他脊椎动物的进化和系统发育研究，因此关于自然层级和相关问题的大多数讨论都是基于硬组织，并且最近是基于分子数据。在这里，我们提供了基于对所有主要脊椎动物类群的比较肌肉学研究以及对硬骨鱼和四足动物（包括灵长类动物）的肌肉系统发生和贝叶斯系统发育分析的第一个讨论这些主题。我们特别（i）反驳了自然层级或进化渐进趋势的概念，这些趋势导致“高级”动物的复杂性增加，并最终导致智人，以及（ii）强调反驳这些旧观念并不一定意味着人们不应该继续使用“系统发育基础”和特别是“解剖学原始”等术语来指代四足动物中的蝾螈类，或灵长类中的灵长目和狐猴类等群体。本综述将有助于提高我们对这些广泛的进化问题和脊椎动物 Bauplans 进化的理解，并有望激发对这些类群的未来系统发育、进化和发育研究。
