Anthropological Institute and Museum, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Nature. 2011 Nov 9;480(7375):91-3. doi: 10.1038/nature10629.
The human brain stands out among mammals by being unusually large. The expensive-tissue hypothesis explains its evolution by proposing a trade-off between the size of the brain and that of the digestive tract, which is smaller than expected for a primate of our body size. Although this hypothesis is widely accepted, empirical support so far has been equivocal. Here we test it in a sample of 100 mammalian species, including 23 primates, by analysing brain size and organ mass data. We found that, controlling for fat-free body mass, brain size is not negatively correlated with the mass of the digestive tract or any other expensive organ, thus refuting the expensive-tissue hypothesis. Nonetheless, consistent with the existence of energy trade-offs with brain size, we find that the size of brains and adipose depots are negatively correlated in mammals, indicating that encephalization and fat storage are compensatory strategies to buffer against starvation. However, these two strategies can be combined if fat storage does not unduly hamper locomotor efficiency. We propose that human encephalization was made possible by a combination of stabilization of energy inputs and a redirection of energy from locomotion, growth and reproduction.
人类大脑在哺乳动物中脱颖而出，其体积异常庞大。昂贵组织假说通过提出大脑和消化道大小之间的权衡来解释其进化，而人类消化道的大小比我们体型的灵长类动物预期的要小。尽管这一假说被广泛接受，但迄今为止，经验证据一直存在争议。在这里，我们通过分析 100 种哺乳动物物种的大脑大小和器官质量数据，在一个包括 23 种灵长类动物的样本中对其进行了测试。我们发现，在控制去脂体重后，大脑大小与消化道或任何其他昂贵器官的质量没有负相关，从而反驳了昂贵组织假说。尽管如此，与大脑大小与能量之间存在权衡的观点一致，我们发现哺乳动物的大脑和脂肪组织的大小呈负相关，这表明脑化和脂肪储存是补偿策略，可以缓冲饥饿。然而，如果脂肪储存不会过度影响运动效率，那么这两种策略可以结合起来。我们提出，人类的大脑化是通过稳定能量输入和将能量从运动、生长和繁殖中重新定向的结合来实现的。
