Australopithecus anamensis
Cambodja
Though not recognized as such for 30 years, the first Australopithecus anamensis discovery occurred in the Kanapoi region of East Lake Turkana in 1965 by a Harvard University expedition.The initial find consisted of a partial left humerus [Johanson and Edgar, 1996]. Aside from a solitary molar discovery in 1982, virtually no further A. anamensis specimens were found until the early 1990's, at which time, Meave Leakey and other affiliates of the National Museums of Kenya organized a research team for the Kanapoi region [Coffing, et al, 1994].
CLASSIFICATION
These 4 million year-old hominid fossils from East Turkana, Kenya, were initially, albeit tentatively, classified as members of Australopithecus afarensis by Kate Coffing, Craig Feibel, Meave Leakey, and Alan Walker in 1994. Meave Leakey and associates, following successful field seasons in the early 1990's, and taking note of the apparent differences between these early Kenyan hominids and typical members of Australopithecus afarensis, reclassified the specimens in 1995. The new species designation was Australopithecus anamensis ("anam" = "lake" in the Turkana language).
GEOLOGICAL SETTING
All A. anamensis fossils were found within a single region, East of Lake Turkana, which is dominated by Pliocene sedimentary sequences. This area includes Kanapoi and Allia Bay, the two most important locales from which these hominids come. The Kanapoi sequence contains strata which were deposited during the an interval between 4.17 and 3.5 million years ago [Leakey, et al, 1995]. This sequence has produced hominid remains from two different levels. The lower level's location, between two layers of volcanic ash (dated to 4.17 and 4.12 million years, respectively), allows a secure date of 4.1 million years to be assigned. The lower level was deposited at a time when an ancient lake, Lake Lonyumun, dominated the landscape. Though most of the Australopithecus anamensis specimens were taken from this level, the assemblage does not include any postcranial material, and mainly consists of elements of this hominid's dentition [Andrews, 1995].
The upper level at Kanapoi can be dated between 4.1 and 3.5 million years ago. Though these chronological boundaries seem to be very secure, it is not clear how closely related the upper and lower levels may be temporally [Leakey, et al, 1995]. Fossils here were found in the context of a small river channel below the locally occurring Kanapoi Tuff, which is about 3.5 million years old. This level has produced important postcranial remains, including the distal humerus from 1965 and a largely complete tibia [Andrews, 1995]. Abundant vertebrate faunas from Kanapoi suggest an open, bushy, or wooded environment [Leakey, et al, 1995], which most-likely varied substantially from place to place.
