Continued Paleoanthropological Investigations at the Hadar Hominid Site, Ethiopia

对300万至400万年前的人类进化的科学理解主要是基于从埃塞俄比亚哈达尔遗址获得的信息。自20世纪70年代初以来，现供职于亚利桑那州立大学人类起源研究所(IHO)的古人类学家在哈达尔遗址进行了九个季节的野外工作。这项研究已经产生了近350个原始人标本，其中绝大多数属于3.0-3.4Myr时间段，并被归因于南方古猿阿法斯物种。包括在哈达尔原始人样本中的是“Lucy”，这是A.L.333年至少13个个体的碎片遗骸，以及该物种第一个相当完整的头骨(A.L.444-2)。人类化石记录中持续存在的数据空白之一是在3.0到2.0年之间，在这段时间里，见证了专门的、巨齿类“强壮的”南方古猿谱系的多样化，以及我们自己的人的崛起。在哈达尔遗址的东段和西段，代表这一区间的沉积物沿着Aawash河支流出露。2.5--1976年，H.Roche和J.Harris和S.Semaw在戈纳支流边缘的一些地方挖掘了Myr Oldowan石器。1994年，IHO小组在Kada Hadar支流沿线裸露的年轻沉积物中进行了实地工作，发现了AfHomo人的一个原始人上颌。能人(A.L.666-1)和2.33Myr沉积物表面的石器。一次小规模的试掘发现了原位工具和零碎的动物遗骸。地质学和动物学研究推断，2.95Myr之后，哈达尔发生了显著的转向更干燥、更开阔的条件，表现为位于重大侵蚀事件(所谓的主要不整合面，简称MDS)上方的沉积物。最终目标是，两年的研究计划是增加哈达尔关于这一人类化石记录中相对鲜为人知的时期的文献证据。在发掘石器和骨骼共同存在的更多地点的同时，将进行火山特弗拉对比研究和古地磁采样，以实现更精细地分辨后MDS序列的时间框架。此外，这项研究计划还包括对独特的A.L.333A.afarensis地点的进一步挖掘，在发现该地点20年后，仍在继续发现原始人化石。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。这些区域是已知的化石，似乎位于关键的2.0-3.0Myr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.