Centre for Cultural Evolution and Department of Zoology Stockholm University, Stockholm, Sweden.
Institute for Future Studies, Stockholm, Sweden.
PLoS One. 2019 Jul 22;14(7):e0218655. doi: 10.1371/journal.pone.0218655. eCollection 2019.
Primate brains differ in size and architecture. Hypotheses to explain this variation are numerous and many tests have been carried out. However, after body size has been accounted for there is little left to explain. The proposed explanatory variables for the residual variation are many and covary, both with each other and with body size. Further, the data sets used in analyses have been small, especially in light of the many proposed predictors. Here we report the complete list of models that results from exhaustively combining six commonly used predictors of brain and neocortex size. This provides an overview of how the output from standard statistical analyses changes when the inclusion of different predictors is altered. By using both the most commonly tested brain data set and the inclusion of new data we show that the choice of included variables fundamentally changes the conclusions as to what drives primate brain evolution. Our analyses thus reveal why studies have had troubles replicating earlier results and instead have come to such different conclusions. Although our results are somewhat disheartening, they highlight the importance of scientific rigor when trying to answer difficult questions. It is our position that there is currently no empirical justification to highlight any particular hypotheses, of those adaptive hypotheses we have examined here, as the main determinant of primate brain evolution.
灵长类动物的大脑在大小和结构上存在差异。有许多假说试图解释这种差异，并且已经进行了许多测试。然而，在考虑了身体大小之后，剩下的可解释的部分就很少了。对于剩余变异，提出的解释变量很多，并且彼此之间以及与身体大小都存在相关性。此外，分析中使用的数据集通常较小，尤其是考虑到许多提出的预测因素。在这里，我们报告了从六个常用的大脑和新皮质大小预测因素中详尽组合得出的完整模型列表。这提供了一个概述，说明了当改变包含不同预测因素时，标准统计分析的输出会如何变化。通过使用最常用的大脑数据集和包含新数据，我们表明，所包含变量的选择从根本上改变了关于是什么驱动灵长类动物大脑进化的结论。因此，我们的分析揭示了为什么研究难以复制早期的结果，而是得出了如此不同的结论。尽管我们的结果有些令人沮丧，但它们强调了在尝试回答困难问题时科学严谨性的重要性。我们的立场是，目前没有经验依据可以突出任何特定的假说，即我们在这里检查的适应性假说，作为灵长类动物大脑进化的主要决定因素。
