Terhune Claire E, Kimbel William H, Lockwood Charles A
Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Box 872402, Tempe, AZ 85287-2402, USA.
J Hum Evol. 2007 Jul;53(1):41-60. doi: 10.1016/j.jhevol.2007.01.006. Epub 2007 May 23.
Although the level of taxonomic diversity within the fossil hominin species Homo erectus (sensu lato) is continually debated, there have been relatively few studies aiming to quantify the morphology of this species. Instead, most researchers have relied on qualitative descriptions or the evaluation of nonmetric characters, which in many cases display continuous variation. Also, only a few studies have used quantitative data to formally test hypotheses regarding the taxonomic composition of the "erectus" hypodigm. Despite these previous analyses, however, and perhaps in part due to these varied approaches for assessing variation within specimens typically referred to H. erectus (sensu lato) and the general lack of rigorous statistical testing of how variation within this taxon is partitioned, there is currently little consensus regarding whether this group is a single species, or whether it should instead be split into separate temporal or geographically delimited taxa. In order to evaluate possible explanations for variation within H. erectus, we tested the general hypothesis that variation within the temporal bone morphology of H. erectus is consistent with that of a single species, using great apes and humans as comparative taxa. Eighteen three-dimensional (3D) landmarks of the temporal bone were digitized on a total of 520 extant and fossil hominid crania. Landmarks were registered by Generalized Procrustes Analysis, and Procrustes distances were calculated for comparisons of individuals within and between the extant taxa. Distances between fossil specimens and between a priori groupings of fossils were then compared to the distances calculated within the extant taxa to assess the variation within the H. erectus sample relative to that of known species, subspecies, and populations. Results of these analyses indicate that shape variation within the entire H. erectus sample is generally higher than extant hominid intraspecific variation, and putative H. ergaster specimens are significantly different from other specimens in H. erectus (sensu lato). However, shape distances within geographical groups of H. erectus are also high, and OH 9 and Dmanisi 2280 are morphologically distinct from the Koobi Fora specimens that are sometimes classified as H. ergaster. These findings suggest that, although H. erectus may be composed of multiple species, the differentiation is complex, and specimens cannot easily be grouped geographically or chronologically. Consequently, more complicated scenarios seeking to explain the observed variation within H. erectus must be considered.
尽管化石人族物种直立人（广义）内部的分类多样性水平一直存在争议，但旨在量化该物种形态的研究相对较少。相反，大多数研究人员依赖于定性描述或对非度量性状的评估，而这些性状在许多情况下呈现出连续变化。此外，只有少数研究使用定量数据来正式检验关于“直立人”类群分类组成的假设。然而，尽管有这些先前的分析，也许部分是由于评估通常被归为直立人（广义）的标本内部变异的方法多种多样，且普遍缺乏对该分类单元内变异如何划分的严格统计检验，目前对于这个群体是一个单一物种，还是应该分成不同的时间或地理界定的分类单元，几乎没有共识。为了评估直立人内部变异的可能解释，我们以大猩猩和人类作为比较分类单元，检验了一个总体假设，即直立人颞骨形态的变异与单一物种的变异一致。在总共520个现存和化石类人猿颅骨上，对颞骨的18个三维（3D）地标进行了数字化处理。通过广义普罗克汝斯分析对地标进行配准，并计算普罗克汝斯距离，用于比较现存分类单元内部和之间的个体。然后将化石标本之间以及化石的先验分组之间的距离与现存分类单元内计算出的距离进行比较，以评估直立人样本相对于已知物种、亚种和种群的变异情况。这些分析结果表明，整个直立人样本的形状变异通常高于现存类人猿的种内变异，并且推定的匠人标本与直立人（广义）中的其他标本有显著差异。然而，直立人地理群体内部的形状距离也很高，OH 9和德马尼西2280在形态上与有时被归类为匠人的科比福拉标本不同。这些发现表明，尽管直立人可能由多个物种组成，但分化是复杂的，标本不能轻易地按地理或时间进行分组。因此，必须考虑更复杂的情况来解释在直立人内部观察到的变异。
