Department of Anthropology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
Am J Phys Anthropol. 2010 Dec;143(4):579-90. doi: 10.1002/ajpa.21354.
The evolution of encephalization requires that energetic challenges be met. Several hypotheses, such as the maternal energy and expensive tissue hypotheses, have been proposed to explain how some species are able to provide adequate energetic resources for large brains. The former incorporates maternal investment strategies, such as extended life history and elevated resting metabolic rate, which contribute to the growth of a large brain. The latter incorporates the reduction of gut size, which increases available energy for the maintenance of adult brain size. This study examines a sample of strepsirrhines, testing the hypothesis that encephalized species utilize some combination of the above-mentioned strategies. Infants and juveniles from three species at the Duke Lemur Center (DLC) were measured periodically to arrive at head and body growth trajectories. These data were used to determine the energetic tradeoff among the offspring. The examination of gestation length, weaning age, intestinal size and resting metabolic rate was used to assess adult brain maintenance and maternal energetic contribution. The results reveal that Daubentonia, the most encephalized and thus human-like of the lemurs, does not experience an energetic trade-off between brain and body during ontogeny, but does exhibit a trade-off between extensive brain growth and possibly reduced intestinal growth. Also, maternal energy is utilized. Encephalized lemurs, such as Daubentonia, have higher resting metabolic rate, while encephalized lorisiforms have a longer period of gestation. These results demonstrate that there are several strategies for meeting the energetic demands of encephalization, and they can be manifested differentially across taxa.
脑化的进化要求满足能量挑战。已经提出了几种假说，例如母体能量假说和昂贵组织假说，以解释为什么有些物种能够为大脑提供足够的能量资源。前者包含母体投资策略，例如延长生命史和提高静息代谢率，这有助于大脑的生长。后者包含肠道大小的减少，这增加了维持成年大脑大小的可用能量。本研究检查了一组懒猴类的样本，测试了脑化物种利用上述策略组合的假说。来自杜克狐猴中心（DLC）的三个物种的婴儿和幼崽定期被测量，以得出头部和身体的生长轨迹。这些数据用于确定后代之间的能量权衡。对妊娠期、断奶年龄、肠道大小和静息代谢率的检查用于评估成年大脑维持和母体能量贡献。结果表明，在发育过程中，最脑化的、最类似于人类的狐猴 Daubentonia 并没有在大脑和身体之间经历能量权衡，但在广泛的大脑生长和可能减少的肠道生长之间确实存在权衡。此外，还利用了母体能量。像 Daubentonia 这样脑化的懒猴具有更高的静息代谢率，而脑化的懒猴类则有更长的妊娠期。这些结果表明，有几种策略可以满足脑化的能量需求，并且可以在不同的分类群中表现出差异。
