Department of Anatomy, Midwestern University, 19555 N. 59th Ave., Glendale, AZ 85012, USA.
Department of Anthropology, Southern Connecticut State University, 501 Crescent St., New Haven, CT 06515, USA.
J Hum Evol. 2022 Jan;162:103102. doi: 10.1016/j.jhevol.2021.103102. Epub 2021 Dec 8.
Two Early Pleistocene fossils from Gona, Ethiopia, were originally assigned to Homo erectus, and their differences in size and robusticity were attributed to either sexual dimorphism or anagenetic evolution. In the current study, we both revisit the taxonomic affinities of these fossils and assess whether morphological differences between them reflect temporal evolution or sexual variation. We generated virtual reconstructions of the mostly complete ∼1.55 Ma DAN5/P1 calvaria and the less complete 1.26 Ma BSN12/P1 fossil, allowing us to directly compare their anterior vault shapes using landmark-based shape analysis. The two fossils are similar in calvaria shape to H. erectus and also to other Early Pleistocene Homo species based on a geometric morphometric analysis of calvaria landmarks and semilandmarks. The DAN5/P1 fossil bears a particularly close affinity to the Georgian H. erectus fossils and to KNM-ER 1813 (H. habilis), probably reflecting allometric influences on vault shape. Combined with species-specific traits of the neurocranium (e.g., midline keeling, angular torus), we confirm that these fossils are likely early African H. erectus. We calculated regression-based estimates of endocranial volume for BSN12/P1 of 882-910 cm based on three virtual reconstructions. Although BSN12/P1 is markedly larger than DAN5/P1 (598 cm), both fossils represent the smallest adult H. erectus known from their respective time periods in Africa. Some of the difference in endocranial volume between the two Gona fossils reflects broader species-level brain expansion from 1.77 to 0.01 Ma, confirmed here using a large sample (n = 38) of H. erectus. However, shape differences between these fossils did not reflect species-level changes to calvaria shape. Moreover, the analysis failed to recover a clear pattern of sexually patterned size or shape differences within H. erectus based on our current assessments of sex for individual fossils.
来自埃塞俄比亚贡纳的两个早更新世化石最初被归入直立人，它们在大小和粗壮程度上的差异归因于性二型或进化趋同。在当前的研究中，我们重新审视了这些化石的分类亲缘关系，并评估了它们之间的形态差异是否反映了时间进化或性变异。我们对大部分完整的约 1.55 Ma DAN5/P1 颅骨和不太完整的 1.26 Ma BSN12/P1 化石进行了虚拟重建，使我们能够使用基于标志的形状分析直接比较它们的前颅顶形状。这两个化石在颅骨形状上与直立人相似，也与其他早更新世的人类物种相似，这是基于颅骨标志和半标志的几何形态测量分析得出的。DAN5/P1 化石与格鲁吉亚的直立人化石和 KNM-ER 1813（能人）最为相似，这可能反映了颅骨形状的比例影响。结合神经颅骨的种特异性特征（例如，中线隆凸，角形脑环），我们确认这些化石可能是早期非洲直立人。我们根据三个虚拟重建计算了 BSN12/P1 的基于回归的内颅容量估计值为 882-910cm³。尽管 BSN12/P1 明显大于 DAN5/P1（598cm³），但这两个化石代表了非洲各自时期已知的最小成年直立人。两个贡纳化石之间的一些内颅容量差异反映了从 1.77 到 0.01 Ma 的更广泛的种级大脑扩张，这在此处使用了大量的直立人样本（n=38）得到了证实。然而，这些化石之间的形状差异并没有反映出颅骨形状的种级变化。此外，根据我们对单个化石的性别评估，该分析未能恢复到直立人性别模式大小或形状差异的清晰模式。
