Antón Susan C
Department of Anthropology, New York University, New York, NY 10003, USA.
Folia Primatol (Basel). 2007;78(5-6):365-88. doi: 10.1159/000105150. Epub 2007 Sep 7.
The nature of the human fossil record is less than ideal for the generation of precise correlations between environmental variables and patterns of evolution in specific lineages. Nonetheless, a critical look at what can and cannot be said from individual fossil morphology and the correlation of specific environmental proxies with specific hominin fossils may lead to a greater understanding of the degree of certainty with which we should embrace environmental hypotheses for the evolution of Homo. Climate shifts have been implicated in both the origin of the genus and its dispersal from Africa. Here, I consider three areas in which a climatic influence has been posited to explain evolutionary shifts in the genus Homo: the origin and dispersal of the genus from Africa; geography, climate and body size in early Homo, and the influence of climate-induced sea level rise on morphological isolation in H. erectus. Each of the data sets is far from ideal, and interpretations of each of the data sets are fraught with issues of equifinality. Of the three hypotheses discussed, the clearest link is seen between latitudinal variation (and presumably temperature) and body size in H. erectus. Similarly, climate-induced sea level change seems a reasonable isolating mechanism to explain the pattern of cranial variation in later Asian H. erectus, but the distribution could also reflect incompletely sampled clinal variation. Alternatively, only equivocal support is found for the influence of climate on the differentiation of H. erectus from H. habilis (as proxied by body/brain size scaling), and therefore the dispersal of the genus Homo cannot be as clearly linked to changes in body size and shape as it has been in the past. These preliminary data suggest that an emphasis on understanding local adaptation before looking at global (and specific) level change is critical to elucidating the importance of climatic factors on the evolution of the genus Homo.
人类化石记录的性质并不理想，难以在环境变量与特定谱系的进化模式之间建立精确的关联。尽管如此，仔细审视从个体化石形态以及特定环境指标与特定古人类化石的相关性中所能得出和不能得出的结论，可能会让我们更清楚地了解，对于人类进化的环境假说，我们应该在多大程度上予以肯定。气候变化被认为与人类属的起源及其从非洲的扩散都有关系。在此，我考虑三个被认为气候产生影响以解释人类属进化转变的领域：人类属从非洲的起源与扩散；早期人类的地理、气候与体型，以及气候导致的海平面上升对直立人形态隔离的影响。每个数据集都远非理想状态，对每个数据集的解释都充满了等效性问题。在讨论的三个假说中，在直立人的纬度变化（大概还有温度）与体型之间能看到最清晰的联系。同样，气候导致的海平面变化似乎是一个合理的隔离机制，可以解释后期亚洲直立人的颅骨变异模式，但这种分布也可能反映了未被充分采样的渐变变异。另外，对于气候对直立人从能人分化（以身体/大脑大小比例衡量）的影响，只找到模棱两可的支持，因此，人类属的扩散与体型和形状变化的关联可能不像过去认为的那么清晰。这些初步数据表明，在研究全球（和特定）层面的变化之前，着重理解局部适应性对于阐明气候因素在人类属进化中的重要性至关重要。
