Lucy daka bodo biology answer

Anthropology

R E P O R T S

However, the absence of abundant lithic as- semblages at these Hata archaeology sites requires explanation.

At the nearby Gona site, abundant Oldowan tools were made and discarded immediately adjacent to cobble conglomerates that ofïered excellent, easily accessible raw materials for stone-tool manufacture. It has been suggested thai the surprisingly advanced character of this earliest Oldowan technology was conditioned by the ease of access to appropriate fine-grained raw materials at Gona {10). Along the Karari escarpment at Koobi Fora (13). the basin mar- gin at Fcjej ( 14). and the lake margin at Olduvai Gorge {12), hominids also had easy access to nearby outcrops of raw material. In contrast, the diminutive nature ofthe Oldowan assemblages in ilie lower Omo [made on tiny quartz, pebbles {15)] was apparently conditioned by a lack of available large clasts.

Tlie situation on the Hata lake margin was even more difficult for early toolmakers. Here, raw materials were not readily available becau.se of the absence of streams capable of carrying even pebbles. There were no neiirby basalt out- crops. The absence of locally available raw ma- terial on the flat featureless Hata lake margin may explain the absence of lithic artifact con- centrations. The bone modification evidence demonstrates that early hominids were trans- porting stone to Ihe site of carcass manipulation. The paucity of evidence for lithic artifact aban- donment at these sites suggests that these early hominids may have been curating their tools (cores and flakes) with foresight tbr subsequent use. Indications of tool curation by later homi- nids have been found at the more recent Pleis- tocene sites of Koobi Fora [Karari escarpment versus Ileret (¡3)] and Swartkrans [polished bone tools in a single repository {16)],

Additional research into the Hata beds may allow a determination of whether Ihe butchery is related to hunting or scavenging. The Bouri discoveries show that the earliest Pliocene archaeological assemblages and their landscape patterning are strongly condi- tioned by the availability of raw material. They demonstrate that a major function ofthe earliest known tools was meat and marrow processing of large carcasses. Finally, they e.xtcnd this pattern of butcher)' by hominids well into the Pliocene,

References and Notes 1. B. Asfaw et ai. Science 284, xxx (1999). 2. N. J. Hayward and C. J. Ebinger, Tectonics I S , 244

(1996). 3. ] . E. Kalb et ai. Nature 298, 17 (1982). Eleven years

later, J. E, Kalb et ai [Newsl. Stratigr. 29, 21 (1993)] tollowed Clark et al. (4) in reversing Daka/Bodo Member order,

4. J. D. Clark e i ai. Nature 307, 423 (1984). 5. J. D. Clatk e£ ai., Sc/ence 264, 1907 (1994). 6. P. R, Renne. C. WoldeCabrieL W. K. H a n , G. Heiken,

T. D. White, Ceo/. Soc. Am. Bull., in press, 7. The age of this standard is now known to be slightly

older [28.02 Ma {17)]. but comparison with previous data (for example, from the Cona) is facilitated by

retaining the standard age of 27.84 Ma. A table of the Ar isotopic data is available at www.sciencemag.org/ feature/data/991110.shl.

8. F. J. Hilgen, Earth Planet. Sei. iett. 107, 249 (1991).

9, The sedimentation rate inferred is conservative be- cause comparison of the *'Ar/*^Ar age w i t h the age of 2.6 Ma (8} for the Gauss/Matuyama boundary more properly requires the use of the older age of the standard (28.02 Ma) and indicates an - 1 0 % greater sedimentation rate.

10. S. Semaw e i ai. Nature 385, 333 (1997),

11. T. D. White, Prehistoric Cannibalism at Mancos SMTUMR-2346 (Princeton Univ, Press, Princeton, NJ, 1992); L R. Binford, Bones: Ancient Men and Modern Myths (Academic Press, New York, 1981): R, J. Blu- menschine,/ Hum. Evol. 29, 21 (1995); S, D, Capaldo and R. J. Blumenschine, Am. Antiq. 59, 724 (1994),

12. R. J. Btumenschine and F. T, Masao, y. Hum. Evoi 2 1 , 451 (1991).

13. G, L. Isaac, Ed., Koobi Fora Research Project Volume 5: Plio-Pleistocene Archaeology (Clarendon, Oxford, 1997).

14. B, Asfaw et at.J. Hum. Evoi 2 1 . 137 (1991).

15. F. C. Howell, P. Haeserts, J. de Heinzelin, ibid. 1 6 , 6 6 5 (1987),

16. C. K. Brain, Ed., Swartkrans: A Cave's Chronicle of Early Man. vol. 8 of Transvaal Museum Monograph Series (Transvaal Museum, Pretoria, 1993),

17. P. R. Renne e i ai. Chem. Ceoi 145. 117 (1998).

18. The Middle Awash paleoanthropobgical project is multinational {13 countries), w i t h interdisciplinary research codirected by B. Asfaw, Y, Beyene, J. D. Clark, T, D. White, and G. WoldeCabriel. The research re-

ported here was supported by NSF, the Ann and Gordon Getty Foundation (8erkeley Geochronology Center), and the Institute of Geophysics and Plane- tary Physics of the University of California and the Earth Environmental Sciences Division at Los Alamos National Laboratory. Additional contributions were made by the Graduate School, the Office for Ad- vancement of Scholarship and Teaching, and the Department of Geology at Miami University. We thank the Ethiopian Mapping Agency and the NASA Goddard Space Flight Center for imagery. We thank H. Gilbert for fieldwork and for work on the illustra- tions. D. Brill made the photographs and G. Richards and B. Plowman at the University of Pacific made the scanning electron microscope (SEM) image. T. Larson provided invaluable field and laboratory geology sup- port. A. Defleur assisted in field survey and excava- tions at BOU-VP-11. We thank H. Saegusa for pro- boscidean Identifications, D. DeGusta for primate identifications and excavations at BOU-VP-12/1, and F. C. Howell for carnivore identifications. We thank O. Lovejoy, G. Suwa, and 6. Asfaw for helpful com- ments. We thank the Ethiopian Ministry of Informa- tion and Culture, the Centre for Research and Con- servation o l the Cultural Heritage, and the National Museum of Ethiopia. We thanü the Afar Regional Government and the Afar people of the Middle Awash for permission and support. We thank the many individuals who contributed to the camp, transport, survey, excavation, and laboratory work that stands behind the results presented.

25 February 1999; accepted 30 March 1999

Australopithecus garhi: A New Species of Early Hominid

from Ethiopia Berhane Asfaw,̂ Tim White,^* Owen Lovejoy,̂ Bruce Latimer/-^ Scott Simpson,^ Cen Suwa^

The lack of an adequate hominid fossil record in eastern Africa between 2 and 3 million years ago (Ma) bas hampered investigations of early hominid phy- logeny. Discovery of 2,5 Ma hominid cranial and dental remains from the Hata beds of Ethiopia's Middle Awash allows recognition of a new species of Aus- tralopithecus. This species is descended from Australopithecus afarensis and is a candidate ancestor for early Homo. Contemporary postcranial remains feature a derived humanlike humeral/femoral ratio and an apelike upper arm-to-lower arm ratio.

The succession of early hominid genera and species indicates diversification into at least two distinci adaptive patterns by - 2 . 7 Ma, A meager east African hominid record hetween 2 and 3 Ma has caused the pattern and pro-

'Rift Valley Research Service, Post Office Box 5717, Addis Ababa, Ethiopia. ^Laboratory for Human Evolu- tionary Studies, Museum of Vertebrate Zoology, and Department of Integrative Biology. University of Cal- ifornia at Berkeley, Berkeley, CA 94720, USA, 'Depart- ment of Anthropology and Division of Biomédical Sciences, Kent State University, Kent OH 44242, USA. 'Cleveland Museum of Natural History and ^Depart- ment of Anatomy, School of Medicine, Case Western Reserve University, Cleveland, OH 44106. USA. ''Uni- versity Museum, University of Tokyo, Hongo, Bunkyo- ku, Tokyo. 113-0033, Japan.

•To whom correspondence shouEd be addressed. E-

mail: timwhite@socrates,berkeley.edu

cess ol'this diversification to remain obscure. The Aitstrahpirheni.'i afarensis (3.6 to 3.0 Ma) to A. aeihiopicus (2,6 Ma) to A. hoi.sci (2,3 to 1.2 Ma) species lineage is well cor- roborated by craniodenial remains. In con- trast, a suggested relationship between A. a/a- ren.si.s and early Homo has previously been evidenced only by relalively uninfoniuilive isolated teeth (/). a palate {2). and a temporal fragment (3).

The recovery ol" hominid lemains from ilie Hala (abbreviation of Hatayae) Member of thi..- Bouri honnalioii -MMS snh îtantially ti) the in- ventor)'oCtossi Is l>earini;on those phyioiieneiK' issues. These remains comprise craniotiental and postcraniai elements trom several areas in the Middle Awash. The first of tliese was dis- covered in ty')O at Matabaietu and Gamedah.

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Biochronology and Ar/Ar daring place these remains at —2.5 Ma. They include a small left parietal fragment (GAM-VP-1/2) and an eden- tulous left mandible corpus from Gamedah (GAM-VP-1/l). as well as a distal left humérus fTom Matabaietu (MAT-VP-1/1). It is impossi- ble to attribute the humérus and parietal frag- ments to a genus. However, tbe small, fluvially abraded Gamedah mandible retains looth roots and corpus contours. Tbese demonstrate that it is not a robust Aitslralopiihccus.

Tt was not until 1996 - 199ÍÍ that we recov- ered addilional hominid remains of compara- ble antiquity west of the modem Awash, at Bouri. The proximal half of an adult hominid ulna (BOU-VP-lI/1) was found on the sur- face of the Hata beds by T. Assebework on 17 Novetnber 1996. On 30 November. White found a proximal femur and associated fore- arm elements of a smaller individual, --I00 m to tbe WNW (BOU-VP-12/1 A-G). Sieving and excavation revealed additional portions of tbis individual's femur in situ. 1 m above a 2.496 Ma voleanie ash. in a horizon with abundant catfish remains and medium-sized bovid fossils, the latter bearing cut marks (-̂ i).

Tbis partial hominid skeleton includes lairly complete shalts oi' a left femur and tbe right hinneruii. radius, and ulna. A partial fibular shaft, a proximal foot phalanx, and tbe base of the anterior portion of the mandible were also found. There is no evidence that these remains represent more tban one individual. Except for the in situ distal femoral shaft segment, all were surface finds lying within 2 m of one another. All are similarly preserved. Lengths can be accurately estimated for the phalatix, the femur, and the three arm elements. The foot phalanx is similar to remains of A. afarensis in size, length, and curvature. The mandible does not retain diagno.stic morphology. No associated hominid teeth were found on the surface or in a large excavation.

Further search of the same —2.5 Ma horizon led 10 the discovery. 278 m farther NNW. of a partial bominid cranium ( BOU-VP-12/130) on 20 November 1997 by Y. Haile-Selassie (Fig. 1). Anotlier individual's crested cranial vault fragment (BOU-VP-12/87) was found 50 m soulb of the BOU-VP-12/1 skeleton excava- rion. At a more northerly locality in the Esa Dibo area —9 km away. A. Defleur found a fairly complete mandible, with dentition, of another hominid individual (BOU-VP-17/1) on 17 November 1997. An additional hotninid hu- meral shaft (BOU-VP-35/1) was found -1 km farther north of the location of the mandible, on 4 December 1998, by D. DeGusta. On bioehro- nologieal grounds, these Esa Dibo specimens are about the same age as the more southerly cluster of hoininid remains at tiouri localities 11 and 12(4).

Great uncertainty has continued to con- found the origin oi'Homo because of a laek of evidence from the intei'val between 2 and 3

Ma (5). The 2.5 Ma Bouri Hata hominids bear directly on tbese issues. In addition, they are closely associated with behavioral evi- dence of lithic technology (4 ). Aii.stralopithe- cu.s africumis from South Africa is roughly contemporary with the Hata remains. In east- em Africa. A. ai'ihiopicns and at least one other putative lineage ancestral to early Homo are contemporaries in (he Turkana Ba- sin. The BOU-VP-12/130 cranial remains represent no previously named species. Only the recovery of additional specimens witb a.ssoeiated crania and dentitions may allow tbe Bouri postcrania to be positively attribut- ed to this new taxon. Therefore, the new species described below is established strictly on tbe basis of craniodental remains.

The following is a description of Attsira-

topiihecus garhi, based on the BOU-VP-12/ 130 specimen: order. Primates Linnaeus 1758; suborder. Antbropoidea Mivart 1S64: genus. Australopithecus DART 1925; and species. Amiraiopithecus garhi.

£tymology. Tbe word garhi means "sur- prise" in tbe Afar language.

Holotj'pe. ARA-VP-12/130 is an associated set of cranial fragments cotnprising the frontal, parietals, and maxilla with dentition. It was found by Y. Haile-Selassie on 20 November 1997. Tbe holotype is housed at the National Museum of Ethiopia. Addis Ababa.

Locality. Bouri Vertebrate Paleontolo- gy locality 12 (BOU-VP-12) is on the east- ern side of the Bouri peninsula, west of the modem Awash River, in the Middle Awash paleoanthropological sttidy area. Afar depres-

Fig. 1. Cranial parts of BOU-VP-12/130. (Top) Superior view of the original fossil. Nonstandard orientation (rotated posteriorly - 1 0 ° from Frankfurt horizontal) to show maximum anatomy. (Bottom) Lateral view of casts to show cranial and maxillary profiles. Note that neither Frankfurt horizontal nor placement of the maxilla relative to the vault can be accurately determined and that reconstructed portions (indicated by oblique lines) are speculative. Photos ©David L. Brill 1999\Atlanta.

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sion, Ethiopia. Tlie BOU-VP-I2/I30 holotype was tbund at 10^15.6199'N, 40°33.8445'E. at -'5Si) m elevation.

Hori/on and associations. The holotype was recovered from silty clays within 2 m of the top ofthe Maoleem vitric tuff, whieh has been dated to 2.496 Ma by Ar/Ar. Vertebrate fossils, including additional hominids, were Ibund at the same stratigraphie horizon on nearby outcrops (4).

Diagnosis.. Au.stralopiihecus garhi is a species of .4uslralopilhccus distinguished from other hominid species by a combination of characters presented in fable I. It is dis- tinguished from .i. ajwcnsis by its absolutely larger postcanine dentition and an upper third premolar morphology with reduced niesio- buccal enamel line projectioEi and less occlu- sal asymmetry, .^mu-alopilhccus ^arlii lacks the suite of derived dental, facial, ¡md cranial

features shared by A. aelhiopicus, A. robus- Im, and A. hoisei. Ausfnilnpithecm garhi is di.stinguished trom A. africamis and other early Homo species by its primilive froiitül. facial, palatal, and subnasal morphology. •*-Dciital description. The postcanine den-

tal si/L' is remarkable, at or beyond tiie known nonrobusl and .-). rahusltis extremes (I-ig. 2). The anterior dentition is also large, with 11 and canine breadths equivalent to or cxceed-

Table 1. List of characters. Listed are characters widely used in consideration of hominid pbylogenetics (IT. 13) that are preserved on the BOU-VP-12/130 bolotype cranium. Because of arbitrary boundaries of presence or absence criteria, variability within species, limited sample sizes, and possible correlation between features, we caution against a numerical ctadistic application of these tabulated data, Ratber, this character list is meant to demonstrate the phenetic status of the single known A. garhi specimen with respect to features used to

evaluate early hominid fossils. Note that despite tbe large postcanine dentition, no shared derived characters link A. garhi with A. robustus or A. boisei. The "early Homo" column comprises specimens assigned by various authors to both H. habilis and H. rudolfensis. Abbreviations are as follows: mod., moderate; asym., asymmetric; disp., disparate; sym., symmetric; rect., rectangular; para., parabolic; var., variable; conv,, convergent; div., divergent; ant., anterior; prom,, prominent; proc, procumbent: cont, continuous; interm., intermediate.

Canine to postcanine ratio Incisor to postcanine ratio Postcanine absolute size UP3 occlusal outline

UP3 mesiobuccal line extension Postcanine PM/M cusp wear Canine lingual sbape Premolar molarizatlon Enamel thickness

Ant. vertical thickness Dental arcade sbape Posterior dental arcade Ant, depth UI2/UC diastema Incisor alveoli relative t o bicanine line

C jugum Ant. pillars Inferolateral nasal aperture margin UI2 root lateral to nasal aperture Canine fossa Maxillary fossula Anterior zygomatic root position Zygomattcoalveolar crest ciivus contour Subnasal prognathism Incisor procumbency Subnasal to intranasal contours Separation of vomeral/ant. septal

insertion Lateral ant. facial contour Facial dishing

Frontal trigon Costa supraorbitalis Temporal line's frontal convergence Postorbital constriction Sagittal crest in male Relative size of posterior temporalis Parietal transverse expansion/tuber Parietomastoid angle Cranial capacity

A. afarensis

large large mod. asym.

frequent disp. asym. none moderately

thirk Ll 111.1^

thin rect. conv. shallow common ant.

prom. absent sharp lateral present absent M l arched convex strong proc. discrete strong

bipartite absent

present present mod. mod. present large absent flared small

A. garhi (n=^)

large smaller large more oval absent disp. asym. minor tbick

thin rect. div. shallow present ant.

prom. absent sharp in line present absent M1-P4 arcbed convex strong proc. discrete strong

bipartite absent

present present mod. mod. present interm. absent weak small

Early Homo

Dentition large large mod. more oval

rare disp. asym. minor thick

Paiate thin para. div. deep rare var.

Lower face var. absent sharp medial var. absent M1-P4 arched flat/convex var. var. discrete usually strong

var. absent

Vault absent torus weak mod. rare interm. present weak enlarged

Males of

A. africanus

large smaller mod. to large more oval

rare disp. asym. minor thick

thin var. div. var. absent ant.

prom. present var. medial present absent M1-P4 var. flat var. var. var. weak

var. absent

absent interm. weak mod. rare interm. absent weak small

A. aethiopicus

(n-l)

unknown smaller? large oval

absent flat unknown pronounced hyperthick

thick recL conv. shallow absent in line

weak absent blunt medial absent absent P4 weak concave strong proc. cont. weak

straight dished

present present strong marked present large absent flared small

A. robustus

small small large oval

absent flat more sym. pronounced hyperthick

tbick para. div. usually deep absent in line

weak present var. medial absent present P4-P3 var. flat to concave weak more vertical cont weak

straight dished

present present strong marked present small absent weak slightly enlarged

A. boisei

small small large oval

absent flat more sym. pronounced hypertbick

thick para. div. deep absent in line

weak absent var. medial absent absent P4/M1-P3 var. flat to concave weak more vertical var. weak

straight dished

present present strong marked present small absent weak slightly enlarged

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ing those of their largest known Australo- pithecus and early Homo homologs. Thus, despite exceptional postcanine size, dental proportions of the holotype deviate markedly from the robust Australopithecus condition. The canine-to-premolar/molar size ratios are comparable to those of .̂ i. afarensis., A. afri- canus, and early Homo. Relative canine to incisor alveolar length is most similar to that OÍA. africanus. Postcaiiine wear, with devel- oped angular facets and retention of buccal cusp saliency. differs distinctively from the robust Australopiihecus pattern. The upper P3 is more derived than that of .4. afarensis and most A. africanus specimens in e.xiiihit- ing a reduced mesiobuccal crown quadrant and a weak transverse crest. The hiiccolingual narrowing of prcmolars and first molars often seen in early Homo is absent.

Cranial description. The lower face is prognathic. with procumbent incisors. Canine roots arc placed well lateral to the nasal aperture margin. The premaxillary surface is separated from the nasal floor by a blunt ridge and is transversely and sagittally con- vex. The palate is vertically thin (~3 mtn at M1/M2 midline). The zygomatic roots origi- nate above P4/MI. The dental arcade is U- shaped, with slightly divergent dental rows (Fig. 3). The temporal lines encroach deeply on the frontal, past the midsupraorbital posi- tion, and probably met anterior to bregma. The postglabellar frontal squama is depressed in a frontal trigon. The localized frontal sinus

is limited to the medial one-third of the su- praorbital surface. Postorbital constriction is marked. The parietal bones have a well- formed, bipartite, anteriorly positioned sagit- tal crest that divides above lambda. An endo- cast was made from the aligned parietals and frontal and was completed by sculpting by R. lloUoway. Crania! capacity was about 450 cm', as measured b\' water displacement.

Taxonomic discussion. There is no cunent agreement about how many pre-erecft/5 Homo species should be recognized or even on how the genus Homo should be defined. The tradi- tional conservative definition emphasizes adap- tive plateau. Ironically, by this definilion. the early Homo species H. rudolfensis and H. ha- bilis miglit be better placed in Australopithecus., as this would affiliate the major adaptive break- throughs in anatomy and behavior that charac- terize H. erectus (ergaster) with the earliest defined occurrence oï Homo. \fA. garhi proves to be the exclusive ancestor of the Homo elade (see discussion below), a cladistic classification might assign it to genus Homo. Here we provi- sionally adopt the conservative, grade-sensitive alternative, emphasizing its small brain and large postcanine dentition by assigning the new Bouri species to .4ustralopitÍK'ctis. This attribu- tion as well as our diagnosis and description may require emendation when additional indi- viduals representing the species are recovered and firm postcranial associations are estab- lished (rt).

Although the Bouri Hata postcrania cannot

presently he assigned to the new species A. garfti., tliey illuminate a.spects of hominid evo- lution. The past few years have witnessed a rash of attempts to estimate early hominid limb length proportions from fragmentary and unas- sociated specimens. These specimens have been used to generate a variety of ftinctional and phylogenetic scenarios. Accurate estimates of the limb proportions of early hominids. how- ever, must be confined to the very lew speci- mens that actually preserve relevant elements, such as the A.L. 288-1 ("Lucy") specimen and KNM-WT 15000. The new Bouri VP-12/1 specimen is only the third Plio-PIoistocene hominid to provide reasonably accurate limb length proportions. The Olduvai Hominid 62 specimen of Homo hahilis has been erroneously argued to show humerus-to-femur proportions more primitive than those of "Lucy" (7, (V), but

its femur length cannot be accurately estimated. Other studies of limb proportions in early Aus- tralopiiiwcus species are based on unassociated joints and not on actual (or even estimated) limb lengths (7).

The postcranial remains recovered from BOU-VP-11, -12, and -35 cannot be conclu- sively allocated to taxon. The BOU-VP-12/1 specimen features a humanlike humeral/fcm- orai ratio (Fig. 4). This ratio may be an important derivation relative to A. ajarensis. because it marks the earliest known appear- ance of the relative femoral elongation that characterizes later hoininids. However, as in A. afarensis, the specimen's brachial index is

Canin« Breadth

BOU-VP-12/130 •

I—I m

10 11 12 13 14 15 mm 12 13 IS 16 17 IB 19 20 mm

1.2-

Helative Canine Breadth

2.2-

Helaüve 11 to C Alveolw LengthFig. 2. Dental size of A. garhi compared with other early hominid taxa and speci- mens. (A) Canine breadth for various taxa. (B) The square root of calculated (MD X BL) premolar area. (C) Tbe square root of calculated (MD x BL} second molar area. (D) Canine breadth relative t o postcanine tooth size for various taxa. (E) Anterior alveolar length (mesial II t o distal C) rela- tive t o postcanine tooth size. In (A) tbrough (C), taxon means, standard deviations, ranges, and sample sizes (in parentheses) are given. All measures were taken by T.W. and G.S. on originals except for A.L. 444-2 and A.L 417-1 (A. afarerisis) and A.L. 666-1 (Homo), which are from (2. 14). Dental metrics for the BOU-VP-12/130 specimen are as follows (XX broken; parentheses = estimate; mesiodistal measure reported first, followed by buccolingual): RII XX, (9.2); R12 6.9, 6.8; RC 11.6.12.9; RP3 (11.0), 16.0; RP4XX, XX; RMl XX, XX; RM2 (14.4), (17.7); RM3 (15.2). 16.9; LÍ2 6.7, 7.0; LC 11.7, 12.9; LP3 (11.4), 16.0; LP4 (11.4). 16.0; LMl (14.4), (16.5), D , A. afarensis: O , A. africanus; A, Horr)o; • , A. robustus: A, A. boisei\ • , BOU-VP-12/130,

I t - C - l1-C..'tM2 Area

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apelike. This suggests thai upper arm-to- lower arm ratios persisted into the basal Pleistocetie and that ihc first hominid with modern forearm proportions was probably ihmo vrectus {ergasicr). Because the A. afa- rensis forearm was also long relative to both the humérus and femur, the femur must have elongated bctbri; Ibreami shortening in early iiominids.

Ihc BOU-VP-11 ulna is from a larger individual, as is the BOU-VP-35/1 humeral shaft (estimated total humeral length ^ 310 to 325 mm). The latter is absolutely longer than the humenis of BOU-VP-12/1 but is less rugose and probably bore a smaller deltopec- toral crest. These differetices (in both size and mgosity) are well within the species ranges of extiint liominoids. If both luimcri represent the same taxon. they could reflect sexual dimorphi.sm. whieh would be comparable to that currently seen in A. afarensis. However, it is perilous to speculate on differences be- tween only two specimens as they may reflect only fluctuating intraspeeific variation in morphology and body mass.

The few and fragmentary nonrobust Tur- kana Basin hominids that span the 2.7 to 2.3 Ma time range are similar lo the Uouri specimens in both size and aspects of morphology. Postca-

nitie dental arcade length of BOU-VP-12/130 is equivalent to that ofOmo 75-14. whereas indi- vidual teeth of the smaller Middle Awash man- dibles (CiAM-VP-l/l and BOU-VP-17/1) are comparable in size to the smaller specimens of the Omo nonrobust collection. It is also impor- tant that BOU-VP-1III exhibits a derived lower P3 morphology (/) most similar to the Omo nonrobust and early Homo conditions and a dental arcade shape concordant with thai of the holotype of ^. garhi.

On the basis of size. BOU-VP-12/130 is a male. The eraniodenta) size dimotphism doc- umented for the closely related A. afarensis and A. boisei therefore predicts smaller indi- viduals in A. garhi. The biochronologically contemporary and morphologically compati- ble BOU-VP-17/] and GAM-VP-l/1 speci- tnens are considerably smaller and may be females. This would suggest a shift in either or both body and dentognathic sizes to aver- ages greater than in A. afarensis. More spec- imens are needed to test this hypothesis.

The diseoveiy of/l. ^arhi provides a strong test of many phylogenetic hypotheses that have addressed the relationships among Plio-Pleisto- cene hominid taxa. The Soutli African species A. africanus was once widely considered to be the most primitive hominid. Discoveries oí A.

afarensis at Hadar and Laetoli displaced A. africanus. This more primitive sister species (.-J. afarensis) was in turn stipplaiitcd when the increasingly older and more primitive sister taxa A. anamensis ( 9) and ArdipiihecLts raniiihi.-i (¡0) were identified. However, the geometry of posi-iifarcnsis hominid phylogeny continues to be the focus of debate.

The position of .1. africanus relative to the emergence of the genus Homo has been par- ticularly difficult to resolve, even in the face of unduly elaborate phylogenetic analyses ( / / ) . One reason for this dillkulty is the fundamental disagreement on whether early Homo comprises one sexually dimorphic {//.

Fig. 3. The most complete palates of A. afarensis (A.L 200-1a; canine reset) (A) and A. boisei (OH-5) (B) compared with that of A. garhi (C and 0). The photograph (©David L Brill 1999\Atlanta) vi/as mirror-imaged on midline. Australopithecus garhi has relatively large canines like A. afarensis and absolutely large but morphologically nonrobust premolars and molars. Drawings ©L. Cudi.

Fig, 4. Probable stages in the progressive differ- entiation of hominid long bone proportions (all bones shown to the same scale). The humérus (top), antebrachium (middle), and femur (bot- tom) are of about equal length in chimpanzees (Pan). Modern bumans differ in two primary ways. Although our humérus is virtually the same length, the femur is elongated and the antebra- chium is shortened. These changes appear to have emerged fully by 1.5 Ma in H. erectus [all three limb segments are virtually complete in KNM-ER- 15000 (75)]. On the basis of the other two partial skeletons in whicb long bone length can now be reliably estimated, the modern human pattern appears to have emerged In two stages: (i) elon- gation of the femur, which is intermediate in length relative to the humérus in A.L 288-1 but exhibits modern proportions in BOU-VP-12/1; and (ii) shortening of the antebrachium, which retains primitive proportions in both specimens (76). Drawings ©I.. Gudz.

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Fig. 5, (A) A cladogram depicting relationships among widely recog- nized early hominid taxa, including the new species A. garhi. Note that an addition- al clade is required vi/hen tVi-o contempo- rary forms of early Homo are recognized A variety of possible cladograms have been generated from the data available in the hominid fossil record, but none of these sat- isfactorily resolve the polychotomy illustrat- ed here (7 7), This cla- dogram adds A, garhi to the unresolved node. (B) The chronological relationships of early bominld taxa. Age is given in Ma. (C t o F) Altemative phytogenies depicting possible rela- tionships among early hominid taxa. Note that

these altematives do not exhaust tbe possibiOties and tbat not all are entirely consistent with the cladogram. It is not presently possible to choose among tbese altematives. . • . ,

hubilis) or two (//. habiiis and H. rudulfen- sis) species. Most phylogenetic efforts have placed A. africanus as the link hetween A, afureiisis and early Homo. This hypothesis has been widely, hul not universally, ac- cepted. Most predicted that a population of A, africanus would be found in eastern Africa when the 2.5 Ma gap there was filled by fossil discoveries.

The 2.5 Ma A. garhi is derived toward me- gadontia from A. afarensis, but in cranial anat- omy it is definitively not A, africanus. Neither is it a repre.sentative ofthe contemporary A, ae- ihiopicus. It is in the right plaee. at the right time, to he the ancestor of early Homo, however defined. Nothing about its morphology would preclude it from occupying this position. The close spatial and temporal association between .-i. ^arlii and behaviors thought to characterize later Homo provide additional circumstantial support. The temporal and possible phyloge- netic placements of various hominid taxa rela- tive to the new speeies from Bouri are reviewed in Pig. 5.

Plio-Pleistocene hominid phylogenetics is hcdeviled hy atomization of functionally coiTe- lated character complexes that probably ema- nate from restricted genomic shifts as well as inadequate fossil samples (particularly for early Homo). Table 1 compiles characters available for A, garhi and related laxa hearing on phylo- genetic placement. The discovery ofthe KNM- WT 17000 specimen of .4. aethiopicus demon- strated the pervasiveness of homoplasy in hom- inid evolution {12). Specimens such as K.NM- ER 1590, KNM-ER 1470, KNM-ER 1802,

Malawi UR 5ÜI, and Omo 75-14 make il ob- vious that some early Homo specimens exhibit megadontia evolved in parallel with robust Aus- fralupithecus, Aitslralopifhecus garhi is cetlain- ly megadont., at least relative to craniofacial size. However, its laek of derived robust char- acters leaves it as a sister taxon to Homo but absent many derived Homo charaeters. A strict- ly cladistic analysis of available data has con- tinually failed to resolve the issue of the posi- tion of A. africanus {! I). Tlie resulting current- ly unresolved polychotomy (Fig, 5) stems fî om the fact that those characters most widely used in early hominid phylogcnetie systematics are predominantly related to masticatory adaptation and are known to be both interdependent and susceptible to parallel evolution. Otlier charae- ters such as cranial base flexion and craniofacial hafting are even more poorly understood. The atomization of such morphological complexes has led to lengthy trait lists, but the valence of the individual "characters" is clearly compro- mised. Such exercises have been useful in es- tablishing the extensive homoplasy present among early hominids, hut such conflnnation only accentuates the precarious nature of phy- logenetic reconstructions based on an incom- plete and highly fragmentary fossil record.

Even a combination of all available tempo- ral, spatial, and (circumstantial) behavioral ev- idence fails to resolve whether the origin of Homo was from South African A. africanus or east African A. afarmsis (or both). We now know that a nonrobust species derived from A. afarensis persisted in eastern Africa until at least 2.5 Ma. Only additional fossils will con-

firm whether this form participated in a rapid evolutionary transition or transitions resulting in an eariy fonn or fomis oí Homo. Such rapid transition may be signaled hy the recently de- scribed A.L. 266-1 palate from Hailar deposits that are claimed to be 2,33 Ma {2). This palate is more derived than thai of A. garhi, \fA. garhi is the direct anceslor of early Homo, as repre- sented by sueh younger specimens as KNM-l-R 1590 and KNM-ER 1470, additional major craniotacial changes must have occurred afkr 2.5 Ma, many of them as direct consequences of brain enlargement. Novel behavioral shifts associated with meat and marrow procurement by means of lithic technology may have played instrumental selective roles during this critical and perhaps short period of evolution.

References and Notes 1. G. Suwa, T. D. White, F, C. Howell, Am. J. Phys.

Anthropoi 101, 247 (1996). 2. W.H.K\tnbe[ et ai.J. Hum. Evol. ^^. S49 (1996); D. C.

Johanson and Y. Rak, Am. J. Phys, Anthropoi 103, 235 (1997).

3. A. Hilf, S. Ward, A. Deino, G. Curtis, R. Drake, Nature 35S, 719 (1992).

4. J. de Heinieün et al.. Sdence 284, 625 (1999). 5. B. A. Vi/ood, Nature 355, 783 (1992). 6. The Chemeron temporal (3) tías been called ttíe

earliest Homo, but the only two characters cited in support of this attribution (a medially positioned mandibular fossa and a sharp petrous crest) are miss- ing from the Bouri holotype, and neither provides unambiguous evidence of brain expansion. Only ad- ditional discoveries will test whether Chemeron is a Kenyan representative of A. garhi.

7. H. M, McHenry and L R. Berger,/ Hum. Evoi 35, 1 (1998).

8. S, Hartwig-Scherer and R, D, Martin, ibid. 2 1 , 439 (1991).

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9, M. G. Leakey, C. S. Feibel, 1, McDougall, A. C. Walker, Nature 376, 565 (1995).

10. T. D. White, C. Suwa, B, Asfaw, ¡bid 3 7 1 , 306 (1994);

ib¡d. 3 7 5 . 8 8 ( 1 9 9 5 ) . n . A. T. Chamberlain and B. A. W o o d , / Hum. Evoi 16.

119 (1987); R. R. Skelton and H. M. McHenry, ¡bid. 23, 309 (1992); D. S. Strait. F. E. Grine, M. A. Monii, ¡bid. 32, 17 (1997); R. R. Skelton and H, M. McHenry, ibld, 34, 109 (1997).

12. F. Ë. Grine, Ed., Evolutionary History of "Robust" Aus- tralopithecines (de Gruyter. New York, 1988): A. C. Walker. R. E. Leakey, J. M. Harris. F. H- Brown. Nature 322. 517 (1986); H. M. McHenry. in Contemporary Issues in Human Evolution, W. E. Meikle. F. C. Howell. N. G. jablonski, Eds. (California Academy of Sciences. San Francisco, 1996), pp. 77-92.

13. W . H . K i m b e l . T D, White. D. CJohanson.-Am./P/iys. Anthropoi 6 4 , 337 (1984); G. Suwa et ai. Nature 389, 489 (1997); P. V. Tobias. Olduvai Corge. Volume 4: The Skulls, Endoeasts and Teeth of Homo habilis (Cambridge Univ. Press. Cambridge. 1991).

14. W. H. Kimbel, D. C. Johanson, Y. Rak. Nature 368, 449 (1994).

15. A. C. Walker and R. E. Leakey. Eds., The Narlokotome Homo erectus Skeleton (Harvard Univ. Press, Cam- bridge. MA. 1993).

16. Femur and humérus length were virtually complete in A.L 288-1 [D. C. johanson et ai.. Am. J. Phys, An- thropoi 5 7 , 4 0 3 0982)1- In B O U - V P - U / 1 . the femur is preserved from the intersection of the medial terminus of the neck with the (missing) femoral head (proximally) to a point on the medial supracondylar line just superior to the gastrocnemius impression (distally). This distance was measured in a sex- and species-balanced sample of Pan. Corilla. and Homo [N - 60) and used to regress (least squares) femoral length [correlation coefficient (K) - 0.9S2: 95% confidence interval of estimate ^ i O . 2 8 ] . This re- gression computes the BOU-VP-12/1 femur at 348 mm. On anatomical grounds, we faeiieve it to have actually been slightly shorter (about 335 mm). Mucfi of the shaft of the BOU-12/1 humérus is preserved, including the point of confluence between the diaph- ysis and the medial epicondylar apophysis and the distalmost extent of the deltopertoral crest. This distance was used to regress humeral length with the same sample (length estimate - 226 m m ; r^ = 0.876: 95% confidence interval of estimate = i 0 . 4 0 ) . On anatomical grounds, we estimate the humérus to have been slightly longer (about 236 mm). Radial length was estimated for A.L. 288-1 with multiple linear regressions from the same sample (breadth distal articular surface; maximum diameter radial head; length radial neck; r' = 0.929; 95% confi- dence interval of estimate = ±0.29) and for 8OU-VP- 12/1 (radial head to nutrient foramen: maximum diam- eter radial head; length radial neck: r^ = 0.937; 95% confidence interval of estimate = -'"0.27). These regres- sions estimate a length of 203 mm for A.L 288-1 and 231 mm for BOU-VP-12/1. On anatomical grounds, the BOU-VP-12/1 estimate appears correct. However, we believe that the A.L 288-1 radius is underestimated on the basis of a lack of sufficient "anatomical space" with which to accommodate all of the preserved pieces of the bone. A regression limited to a sample of common chimpanzees and bonobos {N - 36) estimates a length ot 215 m m (r' - 0.S29; 95% confidence interval of estimate - .' 0.36). This result appears more probable. Only exceptionally pronounced errors in any of the above predictions would alter the conclusions made in the legend of Fig. 3. nor are these conclusions altered by regressions based only on single hominoid species.