Integrative Anatomy Program, Department of Pathology and Anatomical Sciences, University of Missouri, Columbia, MO 65212;
Department of Medical Anatomical Sciences, College of Osteopathic Medicine of the Pacific, Western University of Health Sciences, Pomona, CA 91766-1854.
Proc Natl Acad Sci U S A. 2017 Jun 6;114(23):6000-6004. doi: 10.1073/pnas.1702229114. Epub 2017 May 22.
The evolution of the human pattern of axial segmentation has been the focus of considerable discussion in paleoanthropology. Although several complete lumbar vertebral columns are known for early hominins, to date, no complete cervical or thoracic series has been recovered. Several partial skeletons have revealed that the thoracolumbar transition in early hominins differed from that of most extant apes and humans. , and all had zygapophyseal facets that shift from thoracic-like to lumbar-like at the penultimate rib-bearing level, rather than the ultimate rib-bearing level, as in most humans and extant African apes. What has not been clear is whether had 12 thoracic vertebrae as in most humans, or 13 as in most African apes, and where the position of the thoracolumbar transitional element was. The discovery, preparation, and synchrotron scanning of the partial skeleton DIK-1-1, from Dikika, Ethiopia, provides the only known complete hominin cervical and thoracic vertebral column before 60,000 years ago. DIK-1-1 is the only known skeleton to preserve all seven cervical vertebrae and provides evidence for 12 thoracic vertebrae with a transition in facet morphology at the 11th thoracic level. The location of this transition, one segment cranial to the ultimate rib-bearing vertebra, also occurs in all other early hominins and is higher than in most humans or extant apes. At 3.3 million years ago, the DIK-1-1 skeleton is the earliest example of this distinctive and unusual pattern of axial segmentation.
人类轴状分段模式的进化一直是古人类学中相当有争议的话题。尽管已经有几个完整的腰椎柱为早期人类所知，但迄今为止，还没有发现完整的颈椎或胸椎系列。一些部分骨骼表明，早期人类的胸腰椎过渡与大多数现生猿类和人类不同。这些骨骼都有关节突关节面，它们在倒数第二根肋骨承载的水平而不是大多数人类和现生非洲猿类的最后一根肋骨承载的水平上从类似胸椎的位置向类似腰椎的位置转移。目前还不清楚是像大多数人类一样有 12 节胸椎，还是像大多数非洲猿类一样有 13 节胸椎，以及胸腰椎过渡元素的位置在哪里。来自埃塞俄比亚迪基卡的 DIK-1-1 部分骨骼的发现、准备和同步加速器扫描，提供了 6 万年前之前唯一已知的完整人类颈椎和胸椎。DIK-1-1 是唯一已知的保存了所有七节颈椎的骨骼，并提供了 12 节胸椎的证据，其关节突形态在第 11 胸椎水平发生了变化。这种过渡的位置，即在最后一根肋骨承载的椎骨的一个节段颅侧，也发生在所有其他早期人类中，比大多数人类或现生猿类都要高。在 330 万年前，DIK-1-1 骨骼是这种独特而不寻常的轴状分段模式的最早例子。
