In the late 1960s, the French paleoanthropologist Maurice Taieb started geological exploration of the relatively unexplored area of Ethiopia known as the Afar Triangle, located in the north of the country.
Also known as the Danakil depression or Afar depression, this triangle is the lowest point in Ethiopia and one of the lowest in Africa.
The principal materials for dating East Africa hominid sites are volcanic ashes, yet many of these ashes are not deposited as primary air fall (Greek for ash).
Rather, most are reworked by stream action and are redeposited into the sedimentary environment.
Such numerical calibrations are crucial to understanding rates and timing of evolutionary change.
K-Ar dating has played a key role in unraveling the temporal patterns of hominid evolution as far back as the first significant discovery of East African australopithecines at Olduvai Gorge in 1959.
The four men established the International Afar Research Expedition (IARE), with Johanson in charge of the paleoanthropology aspect of the expedition.
Furthermore, the area had feldspars and volcanic glass that would be valuable for chronometric dating.Further visits to AL 333 resulted in the discovery of 23 additional postcranial and 3 mandibular and dental specimens.This increased the estimate from 13 to at least 17 individuals (9 adults, 3 adolescents, and 5 young children). In 2000, a complete fossil of the fourth metatarsal was recovered from AL 333. afarensis had transverse and longitudinal foot arches and therefore also had a very human-like bipedal gait.Recent advances in K-Ar geochronology, specifically the Ar dating has been a major factor in this success.This grain-discrete method now permits precise and accurate ages to be measured on single grains and, thus, contaminating grains can be eliminated.