New geochronologic and palaeomagnetic data for the hominid-bearing Hadar Formation of Ethiopia

Aronson, James L.; Schmitt, T. J.; Walter, Robert C.; Taieb, Maurice; Tiercelin, Jean-Jacques; Johanson, Donald C.; Naeser, Charles W.; Nairn, A.E.M.

doi:10.1038/267323a0

Cited by 82 publications

(15 citation statements)

References 9 publications

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“…The first rounds of K/Ar dating, conducted by J.L. Aronson at Case Western Reserve University, produced ages broadly consistent with inferences from the fauna (Taieb et al, 1975Aronson et al, 1977;Walter and Aronson, 1982). Thus, the Hadar specimens constituted the first substantial collection of fossil hominin remains securely dated to older than 3 Ma.…”

Section: First Discoveries and Early Impressions Hadarsupporting

confidence: 59%

“Lucy” redux: A review of research on Australopithecus afarensis

Kimbel

Delezene

2009

American J Phys Anthropol

208

140

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In the 1970s, mid-Pliocene hominin fossils were found at the sites of Hadar in Ethiopia and Laetoli in Tanzania. These samples constituted the first substantial evidence for hominins older than 3.0 Ma and were notable for some remarkable discoveries, such as the ''Lucy'' partial skeleton and the abundant remains from the A.L. 333 locality at Hadar and the hominin footprint trail at Laetoli. The Hadar and Laetoli fossils were ultimately assigned to the novel hominin species Australopithecus afarensis, which at the time was the most plesiomorphic and geologically ancient hominin taxon. The discovery and naming of A. afarensis coincided with important developments in theory and methodology in paleoanthropology; in addition, important fossil and genetic discoveries were changing expectations about hominin divergence dates from extant African apes. This coincidence of events ensured that A. afarensis figured prominently in the last 30 years of paleoanthropological research. Here, the 301 year history of discovery, analysis, and interpretation of A. afarensis and its contexts are summarized and synthesized. Research on A. afarensis continues and subject areas in which further investigation is needed to resolve ongoing debates regarding the paleobiol- Just over three decades ago, the east African early hominin species Australopithecus afarensis was recognized as the oldest, most apelike human ancestor. Although specimens now attributed to the species had resided in fossil collections since the 1930s, the bulk of the sample was amassed during field work in the 1970s at two sites, Hadar, Ethiopia, and Laetoli, Tanzania. Today, the species' hypodigm numbers more than 400 specimens collected from a half-dozen sites, most of which are still actively being worked (Table 1). Refinements in radioisotopic dating have established the species' first and last known appearances at 3.7 and 3.0 Ma, respectively. At the time of their discovery, these specimens constituted the first informative sample of hominin fossils older than 3.0 Ma.Studies on subjects ranging from the rise of striding bipedal locomotion to the origin of the uniquely human pattern of growth and development to the evolution of hominin dietary adaptations have drawn heavily on data from the remains of A. afarensis. Taxonomic and phylogenetic research, which experienced a major renaissance in paleoanthropology beginning around the time when A. afarensis was discovered, has benefited from the extensive baseline data on fossil hominin skeletal and dental variation residing in the Hadar site-sample. Some of the research topics that focus on A. afarensis-the extent to which terrestrial bipedality was the committed form of locomotion, the degree of sexual dimorphism in body size and implications for social behavior, and the ''shape'' of the phylogenetic tree prior to the emergence of the Homo and robust australopith lineages, to name just three prominent examples-are still actively debated today, which merely drives home the message that finding solutions to scien...

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Section: First Discoveries and Early Impressions Hadarsupporting

confidence: 59%

“Lucy” redux: A review of research on Australopithecus afarensis

Kimbel

Delezene

2009

American J Phys Anthropol

208

140

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“…The Hadar hominid-bearing strata have been dated by means of potassium-argon, fission track, biostratigraphy, and magnetostratigraphic methods to at least 2.8 Myr, probably no older than 3.3 Myr (Boaz et al, 1982;Brown, 1982), but possibly somewhat cider than 3.6 Myr (Taieb et al, 1976;Aronson et al, 1977;Johanson et al, 1978;Taieb et al, 1978;Walter and Aronson, 1982). The AL 288 partial skeleton shows that the creature was about 107 cm tall, weighed 20 to 23 kg, had forelimbs 83.9% as long as hindlimbs (compared with 73% for H. sapiens, 102% for P troglodytes, 116% for G. gorilla and for P pygmaeus, McHenry, 19781, and was clearly adapted to bipedalism (Johanson and Edey, 1981;Johanson and Taieb 1976;Anonymous, 1976).…”

Section: Fossilsmentioning

confidence: 99%

The capitate of Australopithecus afarensis and A. africanus

McHenry

1983

American J Phys Anthropol

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The capitates of Australopithecus afarensis (AL 288-lw and AL 333-40) and A. africanus (TM 1526) have the identical combination of modern pongid, modern hominid, and unique characteristics. These traits include the combination of a length that is proximodistally shortened (Homo sapiens-like), a facet for the second metacarpal that is distolaterally facing (unique), the reduced styloid process on the third metacarpal (pongidlike), a dorsally placed trapezoid facet (pongidlike), mediolaterally constricted metacarpal III facet (pongidlike), a prominent palmar beak (pongidlike), a single elongated facet for the second metacarpal (H. sapiens-like), a waisted neck (pongidlike), and a reduced amount of "cupping" in the third metacarpal facet (H. sapiens-like). In overall shape the bones are more like H. sapiens than other extant hominids, although they are uniquely different. The two A. afarensis capitates provide no evidence that there are two postcranial morphotypes at Hadar. Available evidence shows that A. afarensis and A. africanus are strikingly similar postcranially. The morphological differences between the capitate of Australopithecus and H. sapiens may relate to the retention of climbing ability and an absence of certain grip capabilities in these early hominids.

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“…Recognizing the importance of the basalt to constraining the age of these hominids, Aronson and coworkers 46 and Walter and Aronson 47 devoted considerable effort to K-Ar dating the basalt. Extensive K and Ar analyses of various fractions separated from the basalt resulted in dates ranging from 2.71 Ϯ 0.25 to 3.80 Ϯ 0.21 Ma.…”

Section: Hadar Ethiopiamentioning

confidence: 99%