Continued Paleoanthropological Investigations at the Hadar Hominid Site, Ethiopia

对300万至400万年前人类进化的科学理解主要基于来自埃塞俄比亚哈达尔遗址的信息。自20世纪70年代初以来，亚利桑那州立大学人类起源研究所（IHO）的古人类学家已经在哈达尔遗址进行了9个季节的实地研究。该研究已获得近350个古人类标本，其中绝大多数属于3.0-3.4 Myr时期的南方古猿阿法种（Australopithecus afarensis）。哈达尔原始人类样本中包括“露西”，这是在A.L. 333处至少13个人的残片遗骸，以及该物种的第一个相当完整的头骨（A.L. 444-2）。原始人类化石记录中持续存在的数据缺口之一是在3.0至2.0亿古年间，这一时期见证了特化的、体型巨大的“强壮的”南方古猿谱系的多样化，以及我们自己的“人属”的兴起。代表这一区间的沉积物在哈达尔遗址的东部和西部沿阿瓦什河支流暴露。1976年，H. Roche和J. Harris以及1992-1993年，S. Semaw在戈纳河支流边缘的一些地方出土了2.5米奥尔多万石器。1994年，国际卫生组织小组对卡达哈达尔支流沿岸暴露的年轻沉积物进行了实地考察，并在2.33 Myr沉积物表面发现了能人上颚（A.L. 666-1）和石器。一次小规模的试掘发现了现场工具和残缺的动物遗骸。地质和动物研究推断，2.95 Myr之后，哈达尔向更干燥、更开放的条件发生了重大转变，这在地层上代表了位于重大侵蚀事件（所谓的大不整合面，或MDS）之上的沉积物。这项为期两年的研究计划的最终目标是在哈达尔增加有关人类化石记录中这一相对鲜为人知的时期的文献证据。对石器和骨骼同时出现的其他地点的挖掘将伴随着火山火山灰对比研究和古地磁采样，以获得更精细的mds后序列时间框架。此外，这项研究计划还包括在独特的A.L. 333阿法种遗址进行进一步的挖掘，该遗址在发现20年后仍在继续出土古人类化石。最后，可以对1970年代初短暂访问过的边远地区进行侦察调查。这些地区已知是化石，似乎处于临界的2.0-3.0迈瑞范围内。

Scientific understanding of human evolution in the period between 3.0 and 4.0 million years ago is based chiefly on information derived from the Ethiopian site of Hadar. Since the early 1970s paleoanthropologists now with the Institute of Human Origins (IHO) at Arizona State University have conducted nine seasons of field work at the Hadar site. This research has yielded nearly 350 hominid specimens, the great majority of which fall within the 3.0-3.4 Myr time period and are attributed to the species Australopithecus afarensis. Included in the Hadar hominid sample are "Lucy," the fragmentary remains of at least 13 individuals at A.L. 333, and the first fairly complete skull of the species (A.L. 444-2). One of the persistent data gaps in the hominid fossil record lies within the period between 3.0 and 2.0 myr, a period that witnessed the diversification of the specialized, megadont "robust" Australopithecus lineage and the rise of our own, Homo. Sediments representing this interval are exposed along Awash River tributaries in both the eastern and western sectors of the Hadar site. 2.5-Myr Oldowan stone tools were excavated at localities on the edge of the Gona tributary in 1976 by H. Roche and J. Harris and in 1992-1993 by S. Semaw. In 1994 the IHO team conducted field work in young sediments exposed along the Kada Hadar tributary and recovered a hominid upper jaw of Homo aff. H. habilis (A.L. 666-1) and stone tools on the surface of 2.33 Myr sediments. A small trial excavation uncovered in situ tools and fragmentary faunal remains. Geological and faunal studies infer a significant shift toward drier, more open conditions at Hadar after 2.95 Myr, represented in sediments stratigraphically situated above a significant erosional event (so-called Major Disconformity Surface, or MDS).The ulitmate goal the two year research plan is to increase the documentary evidence at Hadar concerning this relatively poorly known period in the human fossil record. Excavation of additional localities where stone tools and bones co-occur will be accompanied by volcanic tephra correlation studies and paleomagnetic sampling to achieve a more finely resolved temporal framework for the post-MDS sequence. In addition, this research plan includes further excavations at the unique A.L. 333 A. afarensis locality, which, 20 years after its discovery, continues to yield hominid fossils. Finally, reconnaissance survey of outlying areas that were visited briefly in the early 1970s may be undertaken. These areas are known to be fossilferous and appear to lie within the critical 2.0-3.0 Myr range.