Lague Michael R, Collard Nicole J, Richmond Brian G, Wood Bernard A
Natural Sciences & Mathematics, The Richard Stockton College of New Jersey, Pomona, NJ 08240-0195, USA.
J Anat. 2008 Dec;213(6):670-85. doi: 10.1111/j.1469-7580.2008.00989.x.
Mandibular corpora are well represented in the hominin fossil record, yet few studies have rigorously assessed the utility of mandibular corpus morphology for species recognition, particularly with respect to the linear dimensions that are most commonly available. In this study, we explored the extent to which commonly preserved mandibular corpus morphology can be used to: (i) discriminate among extant hominid taxa and (ii) support species designations among fossil specimens assigned to the genus Homo. In the first part of the study, discriminant analysis was used to test for significant differences in mandibular corpus shape at different taxonomic levels (genus, species and subspecies) among extant hominid taxa (i.e. Homo, Pan, Gorilla, Pongo). In the second part of the study, we examined shape variation among fossil mandibles assigned to Homo (including H. habilis sensu stricto, H. rudolfensis, early African H. erectus/H. ergaster, late African H. erectus, Asian H. erectus, H. heidelbergensis, H. neanderthalensis and H. sapiens). A novel randomization procedure designed for small samples (and using group 'distinctness values') was used to determine whether shape variation among the fossils is consistent with conventional taxonomy (or alternatively, whether a priori taxonomic groupings are completely random with respect to mandibular morphology). The randomization of 'distinctness values' was also used on the extant samples to assess the ability of the test to recognize known taxa. The discriminant analysis results demonstrated that, even for a relatively modest set of traditional mandibular corpus measurements, we can detect significant differences among extant hominids at the genus and species levels, and, in some cases, also at the subspecies level. Although the randomization of 'distinctness values' test is more conservative than discriminant analysis (based on comparisons with extant specimens), we were able to detect at least four distinct groups among the fossil specimens (i.e. H. sapiens, H. heidelbergensis, Asian H. erectus and a combined 'African Homo' group consisting of H. habilis sensu stricto, H. rudolfensis, early African H. erectus/H. ergaster and late African H. erectus). These four groups appear to be distinct at a level similar to, or greater than, that of modern hominid species. In addition, the mandibular corpora of H. neanderthalensis could be distinguished from those of 'African Homo', although not from those of H. sapiens, H. heidelbergensis, or the Asian H. erectus group. The results suggest that the features most commonly preserved on the hominin mandibular corpus have some taxonomic utility, although they are unlikely to be useful in generating a reliable alpha taxonomy for early African members of the genus Homo.
下颌体在古人类化石记录中有着丰富的呈现，但很少有研究严格评估下颌体形态在物种识别中的效用，尤其是那些最常见的线性尺寸。在本研究中，我们探讨了常见保存的下颌体形态可用于以下方面的程度：（i）区分现存的灵长类分类群，以及（ii）支持归为智人属的化石标本的物种划分。在研究的第一部分，判别分析用于测试现存灵长类分类群（即智人、黑猩猩、大猩猩、红毛猩猩）在不同分类水平（属、种和亚种）下颌体形状的显著差异。在研究的第二部分，我们研究了归为智人的化石下颌骨之间的形状变异（包括狭义的能人、鲁道夫人、早期非洲直立人/匠人、晚期非洲直立人、亚洲直立人、海德堡人、尼安德特人和现代人）。一种为小样本设计的新颖随机化程序（并使用组“差异值”）用于确定化石之间的形状变异是否与传统分类法一致（或者，先验分类分组相对于下颌形态是否完全随机）。“差异值”的随机化也用于现存样本，以评估该测试识别已知分类群的能力。判别分析结果表明，即使对于一组相对适度的传统下颌体测量数据，我们也能在现存灵长类的属和种水平上检测到显著差异，在某些情况下，在亚种水平上也能检测到。尽管“差异值”测试的随机化比判别分析更保守（基于与现存标本的比较），但我们能够在化石标本中检测到至少四个不同的组（即现代人、海德堡人、亚洲直立人和一个由狭义的能人、鲁道夫人、早期非洲直立人/匠人以及晚期非洲直立人组成的“非洲智人”组合组）。这四个组在与现代灵长类物种相似或更大的水平上似乎是不同的。此外，尼安德特人的下颌体可以与“非洲智人”的下颌体区分开来，尽管不能与现代人、海德堡人或亚洲直立人群体的下颌体区分开来。结果表明，古人类下颌体上最常见保存的特征具有一定的分类效用，尽管它们不太可能用于为早期非洲智人属成员生成可靠的字母分类法。
