生物谷报道：四年前在乍得发现了被称为Toumai的头骨，从此引发了一场争论。动物学研究表明，该头骨的年龄接近700万年；而其较小的头盖则表明，它的大脑跟黑猩惺的大脑差不多大。发现Toumai的研究小组认为它属于一种原始人类，在黑猩猩与人类的分化中更靠近人类一边，但其他研究人员则认为它更像猿。现在，Toumai物种（Sahelanthrupus tchadensis）牙齿和颌骨碎片的发现表明，该物种与猿相差较远，而与黑猩猩和人类最后的共同祖先关系很近。对Toumai头盖所做的虚拟重建为该物种与人类之间的密切关系提供了更多证据。本期Nature封面上所刊登的是已知最早原始人类的面部。
该文发表在：Nature 434, 752 - 755 (07 April 2005); doi:10.1038/nature03392
New material of the earliest hominid from the Upper Miocene of Chad
MICHEL BRUNET1, FRANCK GUY1,2, DAVID PILBEAM2, DANIEL E. LIEBERMAN2, ANDOSSA LIKIUS3, HASSANE T. MACKAYE3, MARCIA S. PONCE DE LEÓN4, CHRISTOPH P. E. ZOLLIKOFER4 & PATRICK VIGNAUD1
1 Laboratoire de Géobiologie, Biochronologie et Paléontologie Humaine, CNRS UMR 6046, Faculté des Sciences, Université de Poitiers, 40 Avenue du Recteur Pineau, 86022 Poitiers Cedex, France
2 Peabody Museum, Harvard University, 11 Divinity Avenue, Cambridge, Massachusetts 02138, USA
3 Université de N'Djamena, BP 1117, N'Djamena, Tchad
4 Anthropologisches Institut/MultiMedia Laboratorium, Universität Zürich-Irchel, Winterthurerstrasse 190, 8057 Zürich, Switzerland
Correspondence and requests for materials should be addressed to M.B. (michel.brunet@univ-poitiers.fr).
Discoveries in Chad by the Mission Paléoanthropologique Franco-Tchadienne have substantially changed our understanding of early human evolution in Africa. In particular, the TM 266 locality in the Toros-Menalla fossiliferous area yielded a nearly complete cranium (TM 266-01-60-1), a mandible, and several isolated teeth assigned to Sahelanthropus tchadensis and biochronologically dated to the late Miocene epoch (about 7 million years ago). Despite the relative completeness of the TM 266 cranium, there has been some controversy about its morphology and its status in the hominid clade. Here we describe new dental and mandibular specimens from three Toros-Menalla (Chad) fossiliferous localities (TM 247, TM 266 and TM 292) of the same age. This new material, including a lower canine consistent with a non-honing C/P3 complex, post-canine teeth with primitive root morphology and intermediate radial enamel thickness, is attributed to S. tchadensis. It expands the hypodigm of the species and provides additional anatomical characters that confirm the morphological differences between S. tchadensis and African apes. S. tchadensis presents several key derived features consistent with its position in the hominid clade close to the last common ancestor of chimpanzees and humans.
