Institute of Cognitive and Evolutionary Anthropology, University of Oxford, 64 Banbury Road, Oxford OX2 6PN, UK.
Philos Trans R Soc Lond B Biol Sci. 2012 Aug 5;367(1599):2130-40. doi: 10.1098/rstb.2012.0115.
As only limited insight into behaviour is available from the archaeological record, much of our understanding of historical changes in human cognition is restricted to identifying changes in brain size and architecture. Using both absolute and residual brain size estimates, we show that hominin brain evolution was likely to be the result of a mix of processes; punctuated changes at approximately 100 kya, 1 Mya and 1.8 Mya are supplemented by gradual within-lineage changes in Homo erectus and Homo sapiens sensu lato. While brain size increase in Homo in Africa is a gradual process, migration of hominins into Eurasia is associated with step changes at approximately 400 kya and approximately 100 kya. We then demonstrate that periods of rapid change in hominin brain size are not temporally associated with changes in environmental unpredictability or with long-term palaeoclimate trends. Thus, we argue that commonly used global sea level or Indian Ocean dust palaeoclimate records provide little evidence for either the variability selection or aridity hypotheses explaining changes in hominin brain size. Brain size change at approximately 100 kya is coincident with demographic change and the appearance of fully modern language. However, gaps remain in our understanding of the external pressures driving encephalization, which will only be filled by novel applications of the fossil, palaeoclimatic and archaeological records.
由于考古记录中只能提供对行为的有限了解，因此我们对人类认知历史变化的理解很大程度上仅限于识别大脑大小和结构的变化。我们使用绝对和残差脑容量估计值，表明人属脑进化可能是多种过程的结果；100 千年前、100 万年前和 180 万年前的间断变化，加上直立人和广义智人谱系内的逐渐变化，补充了这一结果。虽然非洲人类大脑的增大是一个渐进的过程，但人类进入欧亚大陆与大约 40 万年前和 10 万年前的阶跃变化有关。然后，我们证明人属大脑大小的快速变化期与环境不确定性的变化或长期古气候趋势没有时间上的关联。因此，我们认为，常用的全球海平面或印度洋粉尘古气候记录几乎没有证据表明解释人类大脑大小变化的可变性选择或干旱假说。大约 100 千年前的大脑大小变化与人口变化和完全现代语言的出现同时发生。然而，我们对推动脑进化的外部压力的理解仍然存在差距，只有通过对化石、古气候和考古记录的新应用，才能填补这些差距。
