Gonzalez-Voyer Alejandro, González-Suárez Manuela, Vilà Carles, Revilla Eloy
Conservation and Evolutionary Genetics Group, Department of Integrative Ecology, Estación Biológica de Doñana (EBD-CSIC), c/Américo Vespucio s/n, 41092, Sevilla, Spain.
Department of Zoology/Ethology, Stockholm University, Svante Arrheniusväg 18 B, SE-10691 Stockholm, Sweden.
Evolution. 2016 Jun;70(6):1364-75. doi: 10.1111/evo.12943. Epub 2016 May 30.
Although previous studies have addressed the question of why large brains evolved, we have limited understanding of potential beneficial or detrimental effects of enlarged brain size in the face of current threats. Using novel phylogenetic path analysis, we evaluated how brain size directly and indirectly, via its effects on life history and ecology, influences vulnerability to extinction across 474 mammalian species. We found that larger brains, controlling for body size, indirectly increase vulnerability to extinction by extending the gestation period, increasing weaning age, and limiting litter sizes. However, we found no evidence of direct, beneficial, or detrimental effects of brain size on vulnerability to extinction, even when we explicitly considered the different types of threats that lead to vulnerability. Order-specific analyses revealed qualitatively similar patterns for Carnivora and Artiodactyla. Interestingly, for Primates, we found that larger brain size was directly (and indirectly) associated with increased vulnerability to extinction. Our results indicate that under current conditions, the constraints on life history imposed by large brains outweigh the potential benefits, undermining the resilience of the studied mammals. Contrary to the selective forces that have favored increased brain size throughout evolutionary history, at present, larger brains have become a burden for mammals.
尽管先前的研究已经探讨了大脑为何进化得如此之大的问题，但面对当前的威胁，我们对大脑尺寸增大可能产生的有益或有害影响的了解仍然有限。我们使用新颖的系统发育路径分析方法，评估了大脑尺寸如何通过对生活史和生态的影响，直接和间接地影响474种哺乳动物的灭绝易感性。我们发现，在控制体型的情况下，较大的大脑会通过延长妊娠期、增加断奶年龄和限制产仔数量，间接增加灭绝易感性。然而，我们没有发现大脑尺寸对灭绝易感性有直接的有益或有害影响的证据，即使我们明确考虑了导致易感性的不同类型的威胁。特定目分析显示，食肉目和偶蹄目呈现出定性相似的模式。有趣的是，对于灵长目动物，我们发现较大的大脑尺寸直接（和间接）与更高的灭绝易感性相关。我们的研究结果表明，在当前条件下，大脑对生活史的限制超过了潜在的益处，削弱了所研究哺乳动物的恢复力。与在整个进化历史中有利于大脑尺寸增加的选择力量相反，目前，较大的大脑已成为哺乳动物的负担。
