jaws and teeth ofaustralopithecus afarensis from maka, middle awash, ethiopia

Jaws and Teeth of Australopithecus afarensis From Maka,Middle Awash, Ethiopia

TIM D. WHITE,1* GEN SUWA,2 SCOTT SIMPSON,3AND BERHANE ASFAW4

1Laboratory for Human Evolutionary Studies, Museum of VertebrateZoology, and Department of Integrative Biology, University of California,Berkeley, California 94720-31402University Museum, University of Tokyo, Hongo, Bunkyo-ku,Tokyo 113, Japan3Department of Anatomy, Case Western Reserve University,Cleveland, Ohio 44106-49304Rift Valley Research Service, Addis Ababa, Ethiopia

KEY WORDS mandible; Pliocene; hominid; dentition; Afar

ABSTRACT The Maka locality in Ethiopia’s Middle Awash area hasyielded new craniodental remains dated to 3.4 million years (myr) in age.These remains are described and assessed functionally and systematically.The fossils are assigned to Australopithecus afarensis. Maka thus joins Hadarand Laetoli as the third major locality yielding this species. As with previoussite samples, the Maka collection displays a wide range of size variation. Thenearly complete and undistorted MAK-VP-1/12 adult mandible from Maka isan excellent match for Hadar and Laetoli counterparts, confirming thegeographic and temporal distribution of A. afarensis. This specimen showsthat this taxon is functionally and developmentally hominid in its incisor/canine/premolar complex. A postulated evolutionary trajectory through A.anamensis to A. afarensis would have involved postcanine megadontia andother adaptations to a more heavily masticated diet relative to the earlierArdipithecus ramidus. Am J PhysAnthropol 111:45–68, 2000. r 2000 Wiley-Liss, Inc.

When the species Australopithecus afaren-sis was named in the late 1970s, mandiblesand teeth played a key role in its diagnosisand description (Johanson and White, 1979;Johanson et al., 1978, 1982a). The ensuingdecade witnessed debates over the unity andphylogenetic relationships of this taxon(summarized by Boaz, 1988). The geographicseparation of Laetoli and Hadar, and thevariation seen in the A. afarensis paratypeseries, led some investigators to suggestthat multiple species had been pooled (seediscussion in White, 1985). The reopening ofpaleoanthropological research in Ethiopia in1990 allowed continuation of research in theMaka catchment of the Middle Awash paleo-anthropological study area of Ethiopia.

Pliocene hominids were discovered at Be-lohdelie and Maka on the eastern side of the

Middle Awash paleoanthropological studyarea in 1981 (Asfaw, 1987, 1988; Clark et al.,1984; White, 1984). A return to Maka in theautumn of 1990 resulted in the recovery ofadditional remains, including teeth and jawsattributed to A. afarensis. These specimenshave been precisely placed in a refined chro-nostratigraphic sequence (White et al., 1993;Renne et al., 1999). Subsequent research onthe western side of the study area, at Ara-

Grant sponsor: National Science Foundation; Grant sponsor:Japanese Society for the Promotion of Science; Grant sponsor:Japanese Ministry of Education, Science, Sports, and Culture;Grant sponsor: CWRU Research Initiation Grant Program;Grant sponsor: University of California Collaborative ResearchProgram of the Institute of Geophysics and Planetary Physics atLos Alamos National Laboratory.

*Correspondence to: Tim White, Department of IntegrativeBiology, 3060 VLSB, University of California at Berkeley, Berke-ley, CA 94720-3140. E-mail: [email protected]

Received 23 June 1998; accepted 19 August 1999.

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 111:45–68 (2000)

r 2000 WILEY-LISS, INC.

mis, Sagantole, and Kuseralee Dora, hasyielded remains of hominids attributed toArdipithecus ramidus (White et al., 1994,1995; WoldeGabriel et al., 1994, 1995). Makaprovides the first substantial sample of A.afarensis remains outside of the paratypesites of Hadar and Laetoli. The Maka fossilsprovide fresh data bearing on systematicand functional issues surrounding A. afaren-sis.

The Maka described here sample a timeperiod, (3.0–3.6 million years ago) (myr),that has now yielded fairly abundant fossilsthat have already been afforded detaileddescription in this journal. We subscribe tointerpretations that recognize A. afarensisas the only documented species of earlyhominid occupying that time period. Themandibles and teeth of A. afarensis arewell-known, and specimens recovered in the1970s are fully described elsewhere (White,1977, 1980, White and Johanson, 1982; Jo-hanson et al., 1982b; Suwa, 1990; Suwa etal., 1994, 1996). As will be seen in thecomparative descriptions to follow, the Maka

remains depart in no anatomically signifi-cant way from A. afarensis as defined by theHadar and Laetoli hypodigm. However, theydo offer significant new insights into func-tional and systematic issues surroundingthat taxon.

PROVENIENCE

The Maka specimens described here weresurface finds, but preservational characteris-tics and their relationship to the erodingsediments clearly indicate that they wereembedded in the sands and gravels referredto informally as the ‘‘Maka sands’’ of theMatabaietu Formation. These faunally-richsand and gravel deposits represent pedi-alluviational aggradation into an area of theMiddle Awash previously occupied by exten-sive, relatively deep lakes. The Maka sandswere deposited discomformably about 7 mabove the Cindery Tuff, and 6 m above theVT-3 (5 Wargolo) tuff horizons (Fig. 1). Thesetuffs are dated to 3.85 6 0.083 and 3.74 60.023 myr, respectively (White et al., 1993).Interdigitated with the hominid-bearing

Fig. 1. A view toward the north of the Maka sands in the upper Maka catchment. Arrow indicates apaleontologist in a white hat at the discovery site of the MAK-VP-1/12 mandible. A lens of the Sidiha Koma Tuff(SHT), dated to 3.4 myr, is interfingered in these sands and constrains the age of the Maka hominids.

46 T.D. WHITE ET AL.

Maka sand unit is a volcanic lens, MA90-16,whose glass chemistry we correlate with theSidiha Koma Tuff near the base of the HadarFormation, and with tuff MA90-28 at thenearby Wee-ee fossil locality (White et al.,1993). These units are dated to 3.40 6 0.03myr and 3.39 6 0.036 myr, respectively(Walter and Aronson, 1993; White et al.,1993). Thus, we have high confidence thatthe age of the Maka hominids described hereis ca. 3.4 myr, just slightly older than theearliest hominids recovered from the base ofthe Hadar Formation to the north.

MATERIALS AND METHODS

The 1960s Homo habilis controversy ap-pears to have made a lasting impression onmany workers who subsequently found anddescribed fossils in eastern Africa. Perhapsreluctant to revisit the heated controversiesof the previous decade, 1970s workers pub-lished descriptions of hominid fossils thatavoided phylogenetic and taxonomic conclu-sions. A series of publications largely devoidof explicit comparisons or other systematicconsiderations resulted (e.g., Leakey et al.,1971; Leakey and Wood, 1973; Leakey andWalker, 1973; Day and Leakey, 1973; Day etal., 1976; White, 1977; Johanson et al.,1982a; Leakey and Walker, 1985). Betweenthe initial announcements of fossils (usuallyin Nature) and monographic treatment, theAmerican Journal of Physical Anthropologywas used as the outlet for the disseminationof information about the new hominids fromKoobi Fora, Laetoli, and Hadar. These de-scriptions apparently were not written to beread as text, but rather to provide detailedpublished archival inventories of preserva-tional and anatomical characteristics foreach specimen.

The avoidance of explicit anatomical com-parisons has led to a plethora of specimendescriptions, many of which, in our view, arenot helpful. For example, when a retromolarfossa was described as ‘‘wide’’ in a descrip-tion, did it mean ‘‘wide’’ relative to humans,to gorillas, or to other conspecific individu-als? We recognize that, our views notwith-standing, the place and nature of detailedanatomical descriptions in paleoanthropol-ogy will continue to be debated and modifiedas scanning, archiving, and casting technolo-gies advance. Nevertheless, we wish to go on

record as favoring an explicitly comparativeapproach, which we employ here.

The descriptions that follow are explicitlycomparative. All observations concerningspecimens discussed below were made onthe original fossils. The comparative sampleof A. afarensis used in this analysis includesall published specimens from Laetoli as wellas all Hadar specimens recovered prior to1990. The original Maka remains are perma-nently housed in the PaleoanthropologyLaboratory at the National Museum of Ethio-pia in Addis Ababa. Comparative observa-tions and data on modern ape dentognathicremains were made on the original speci-mens at the Cleveland Museum of NaturalHistory and additional collections describedbelow.

PRESERVATION

MAK-VP-1/2 (Figs. 2, 4b). Adult rightside of a mandible with condyle, M1–M3. Thespecimen was found in 19 pieces by Yo-hannes Haile-Selassie on October 10, 1990.The surface is perfectly preserved except fora few root etchings. All joins were good, andthere is no residual distortion. The specimenlacks most of the gonial angle and coronoidprocess, and little of the base remains. Theteeth show substantial plant root etchingbut are otherwise well-preserved and undis-torted.

MAK-VP-1/4 (Fig. 8d). Right lower M2.This specimen was found by Yohannes Haile-Selassie on October 11, 1990. It is a completecrown without roots.

MAK-VP-1/6 (Fig. 8). Corpus fragmentfrom the left side of a mandible. The speci-men was found by Tim White on October 11,1990. It is very poorly preserved, with thedistal M2 and total M3 roots in place, but notooth crowns. The bone surface is mostlyexfoliated.

MAK-VP-1/12 (Figs. 3–7). Adult man-dible with LI2-M3, RP3-M3, and both con-dyles. The specimen was found by Tim Whiteon October 12, 1990. The first segment foundwas a portion of right corpus with M1. Afterintensive slope collection and sieving, a totalof 109 fragments was found to comprise therestored specimen (Fig. 3). With so manysequential glue joins in the ramus, there is

47A. AFARENSIS FROM MAKA

probably slight distortion, particularly inthe setting of the condyles relative to thedentition. However, the continuity of bonysurface indicates that all structures are

within a millimeter of their true position.The coronoid processes and most of bothgonial angles are missing. The surfaces ofboth rami are weathered and crossed by

Fig. 2. The MAK-VP-1/2 mandible. a: Medial view. b: Occlusal view. c: Anterior view. All natural size.


many fracture lines. The corpus is well-preserved, with some loss of labial alveolarbone across the incisor arcade. Even the thinmental spine is perfectly preserved, butbased on previous experience we predictthat this fragile structure will be broken byfinger or caliper within 3 years of this publi-cation. There is light etching on the bonesurfaces, most pronounced on the left cor-pus, and particularly intensive on the rightcondyle. The teeth are macroscopically well-preserved. Microscopically they all exhibitvarious degrees of postdepositional modifica-tions to their external surfaces. These rangefrom some flaking of the external surface ofthe enamel to mild erosion of the fine surfacedetails.

MAK-VP-1/13 (Fig. 8e). Left upper firstmolar. This specimen was found on October15, 1990 during the sieving operation forMAK-VP-1/12. The crown is fractured andlacks its buccal and mesial faces. Portions ofthe enamel are root-etched.

MAK-VP-1/83 (Fig. 8a). Left mandibularramus. This specimen was found by AlemuAdemassu on October 20, 1990. It was recov-ered in three major fragments that areaccurately restored into one piece. The lat-eral end of the condyle is missing, the medialend is abraded, and the lateral surface of theramus surface is mildly etched by root acids.

The comparative descriptions below focuson the MAK-VP-1/12 specimen because of itscompleteness. They are supplemented,where appropriate, by reference to the fourother dental and mandibular specimens re-covered from the Maka sands during the1990 field season. The single upper tooth isdescribed at the end. Tables 1 and 2 supple-ment the text and photographs. These pro-vide metrics comparable to those previouslypublished for the paratype series of A. afaren-sis.

DESCRIPTIONS

The descriptions of the Maka remains areorganized by tooth and element, not byindividual specimen as presented above. De-scriptions are for MAK-VP-1/12 except wherenoted.

Dentition: macroscopic observationsIndividual teeth.Lower lateral incisor. The crown is worn toapproximately the midcrown point, expos-ing a subrectangular dentine patch 5.0 3 1.4mm. In size, the incisor is near the A.afarensis mean. There is a slight lingualbevel to the occlusal platform. Lingual reliefis minimal, closely matching the A.L.333w-58 specimen.

Lower canine. The crown apex is worn toexpose a 1.5 mm-diameter dentine patch. Inlabial (anatomically lateral) view the occlu-sal wear plane turns abruptly at midcrown,and the flat wear surface slants postero-inferiorly at approximately 45° toward thedistal marginal tubercle. This angulation ofthe occlusal wear surface is also seen inL.H.-14, A.L. 333w-58, A.L. 198-1, and A.L.400a. The often planar wear on the distaledge of A. afarensis lower canines is formedby contact with the mesial incisal ridge ofthe upper canine tooth (as seen in the A.L.200-1a upper canine). In size, shape, andocclusal wear, the Maka canine is a closematch for L.H.-14 and A.L. 400-1a, although

Fig. 3. Pieces from the MAK-VP-1/12 sieve operationpotentially belonging to the hominid mandible. Onehundred and nine of these pieces were reassembled toform the mandible.


Fig. 4. a: MAK-VP-1/12, posterior view. b: MAK-VP-1/2, lateral view. Both natural size.


Fig. 5. MAK-VP-1/12. a: Basal view. b: Left condyle, superior view. c: Cross-sectional view. d: Lateraloblique view of canine ‘‘step.’’ Natural size, except b and c scaled as shown (in millimeter increments).


Fig. 6. MAK-VP-1/12. a: Lateral view. b: Left canine, lingual view. c: Left canine, buccal view. d: Leftcanine, mesial view. e: Left canine, distal view. f: Oblique view of exposed LP3 root. g: RP3, buccal view.h: RP3, mesial view. i: Mesial view of exposed LP3 root within broken mandible. j: Basal view of brokencrown base of the RP3. Buccal at left, mesial at top. All natural size.


Fig. 7. MAK-VP-1/12. The mandible of A. afarensis (center) compared to a modern male commonchimpanzee (right), and a modern human (left). Photograph natural size.


both of the latter specimens have greaterlingual relief. There is a small, ca. 0.3-mmdiastema between the canine and P3.

Lower third premolar. The left P3 is moreheavily worn than the right and exhibits acircular, 0.4 mm diameter apical pit withexposed dentine atop the protoconid. Thecrowns are unequal in size, but near the A.afarensis mean (White et al., 1993). Themetaconid is swollen and weakly separated

from the protoconid by a shallow fissure.The moderately defined anterior fovea at themesiolingual corner of the crown is circum-scribed by weak marginal ridges. Overallcrown shape, anterior foveal development,and occlusal relief and wear are comparableto the HadarA.L. 266-1, 333w-46, and 333-10specimens.

Both right and left root systems consist ofindependent mesial and distal roots (Fig. 6).Both sides exhibit similar morphology, anddetailed observation and measurement waspossible on the right P3 before mandibularassembly. The mesial root is plate-like, witha bucco-lingual breadth of 6.5 mm. It is setmesially and is only weakly oblique to thedistal root, which is 8.4 mm in breadth. Thisroot system approximates the ‘‘molarized’’pattern considered by some to be character-istic of ‘‘robust’’ Australopithecus P3s (e.g.,Wood et al., 1988). Such an incipiently molar-ized condition is also seen occasionally inother ‘‘nonrobust’’ taxa (OMO 18-33,KNM-ER 1814, STW 231/233, and STW240). Natural fracture sections ca. 2–3 mmbelow the cervix reveal single root canals inboth mesial and distal roots, with the distalcanal elongated buccolingually.

Lower fourth premolar. The right P4 ismuch more heavily worn than the left, withdentine exposed in an irregular 1.0–2.0 mm-wide trough down the buccal occlusal sur-face. Right and left crown sizes are asym-metrical, and near the A. afarensis mean.Shape and occlusal relief and wear are closelymatched by the Hadar A.L. 266-1 and 400-1aand Laetoli L.H.-4 specimens.

Lower first molars. The right first molar ismore worn distally, with dentin exposureson the protoconid (1.8 mm, circular), thehypoconid (2.2 diameter) and the hypoconu-lid (0.6 mm). Crown shape is square, andsize is near the A. afarensis mean. Theocclusal morphology and relief are similar tothe Hadar A.L. 333w-60 and Laetoli L.H.-4specimens. The slightly larger and moreheavily worn M1 of the MAK-VP-1/2 indi-vidual is a good match for the Hadar A.L.277-1 specimen, with which it shares a deep,cupped exposure of dentine on the buccalocclusal surface.

Fig. 8. Maka 1990 hominids. a: MAK-VP-1/83 ra-mus, lateral view. b, c: MAK-VP-1/6 mandible corpus,lateral and occlusal views, respectively. d: MAK-VP-1/4lower molar. e: MAK-VP-1/13 upper molar. All naturalsize.


Lower second molars. The new Maka sam-ple comprises four second molars, the firsttwo of which are from MAK-VP-1/12. Crownsize of the latter is near the A. afarensismean. Crown wear on this specimen is highlyasymmetric, with far more dentine wearexposure on the right M2 at both the protoco-nid and hypoconid positions (deep, pitlikeexposures of 3.2 mm diameter and 2.6 mm,respectively). In size, shape, and wear, theright second molar is similar to Hadar A.L.333w-59 and the left is a fair match forL.H.-4. The larger, more heavily worn sec-ond molar of the MAK-VP-1/2 individualbears a deep, extensive dentine wear expo-sure on the hypoconid/hypoconulid and pro-toconid. Its overall crown shape, size, andwear are similar to the Laetoli L.H.-23 M2.The largest of the three Maka individuals atthe M2 position is MAK-VP-1/4. This slightlyworn crown is slightly narrower and longerthan the A.L. 277-1 specimen’s M2. A.L.277-1 is at the high end of the A. afarensisM2 size range.

Lower third molars. The MAK-VP-1/12third molars are nearly equally worn, with-out enamel perforation. The MAK-VP-1/2individual displays a more heavily wornright M3, which also lacks dentine exposure.It is slightly larger. The Maka specimens arenear the A. afarensis mean in crown size. Insize and shape, the Maka specimens liebetween L.H.-4 and A.L. 333w-57.

Upper first molar. The MAK-VP-1/13 speci-men is broken, but its mesiodistal dimen-

sion is the smallest known for A. afarensis.It bears a deep, bilobed protocone dentineexposure that extends from the protocone tothe mesial marginal ridge.

Overall dentition.Macroscopic wear. The MAK-VP-1/12 speci-men exhibits the typical A. afarensis occlu-sal and interproximal wear pattern, in whichthere is a strong wear gradient combinedwith retained cusp saliency. The wear gradi-ent is similar to that seen on the A.L. 288-1and L.H.-4 specimens. The extent of wear onthe Maka dentition is intermediate betweenthese. The Maka postcanine rows showstrong occlusal relief relative to other Austra-lopithecus species, with sharp, occlusallyprojecting metaconid and entoconid edges.The marked asymmetry of occlusal wear(particularly on the P4) is possibly related tothe degenerative changes on the mandibu-lar condyles (see below). The MAK-VP-1/2specimen was an older individual with asteep molar wear gradient.

Proportions. The proportions between an-terior and posterior teeth are very similar tothose seen in other specimens of A. afaren-sis from both Hadar and Laetoli (Fig. 11).

The C/P3 complex. The distal incisal edgeof the MAK-VP-1/12 lateral incisor is leveland continuous with the worn mesial incisalridge of the canine, as it is in the A.L. 400-1aspecimen. However, unlike the A.L. 400specimen, the Maka specimen shows a steep‘‘drop’’ of the occlusal edge across the poste-

TABLE 1. Dental measurements1

I2 C P3 P4 M1 M2 M3 M1

Mesiodistal lengthRightMAK-VP-1/2 13.1 (13.6) 14.7 (15.0) 15.6MAK-VP-1/4 16.2MAK-VP-1/12 (9.7) 9.5 (9.7) 12.6 (13.0) 13.8 (14.2) 14.9 (15.2)LeftMAK-VP-1/12 7.2 (w) 9.5 9.1 (9.3) 8.8 (9.0) 12.8 (13.1) 13.6 (14.0) 14.8 (15.3)MAK-VP-1/13 10.9

Buccolingual breadthRightMAK-VP-1/2 12.4 13.0 13.0MAK-VP-1/4 13.8MAK-VP-1/12 11.3 max 10.8 12.1 13.3 13.4LeftMAK-VP-1/12 8.0 10.2 max 11.2 max 9.9 12.2 13.3 13.4

1 All measurements are in millimeters and follow techniques outlined in Johanson et al. (1982b). Estimates are in brackets. w, worn;max indicates maximum oblique buccolingual measure.


rior surface of the canine (Fig. 5d). In otherwords, there is a marked ‘‘step’’ or ‘‘drop-off’’from the higher incisal/anterior canine edgeto the lower occlusal surface of the thirdpremolar. This would also have been thecase for L.H.-4 as well as for many of theother A. afarensis mandibles. This is verydifferent from the condition in apes, wherethe incisor and premolar occlusal surfacesboth lie inferior to the level of the canineapex. In humans and other species of Austra-lopithecus, the occlusal surfaces of all threecrowns are at about the same height. TheMAK-VP-1/12 specimen shows a small gapbetween the left C and P3, and there are no

interproximal facets on the distal C or me-sial P3 crown faces. Diastema are common inA. afarensis, previously recorded in approxi-mately half of the available sample.

Microscopic wear and enamel thickness. Oc-clusal and interproximal wear are presenton all of the teeth. Although not formallystudied, the molar occlusal microwear isdominated by long, buccolingually orientedstriae. Very few pits or mesiodistally ori-ented striae are observed. This is moresimilar to wear patterns described for A.africanus than A. robustus (dominated bypits) (Kay and Grine, 1988). Additional stud-

TABLE 2. Mandible measurements1

At crownsI1

I2 C P3 P4 M1 M2 M3Between crowns I1/I2 I2/C C/P3 P3/P4 P4/M1 M1/M2 M2/M3

Perpendicular corpus heightRight, at crownsMAK-1/12 x x x (33.0 6 0.5) 31.3 29.7 (27.7 1 1) (28.2 1 1)MAK-1/2 32.6 30.7Right, between crownsMAK-1/12 x x x (36.7 6 0.5) 34.5 31.8 29.2 (27.2 1 1)MAK-1/2 34.6 31.8Left, at crownsMAK-1/12 x x (34.4 6 1) 33.7 33.6 31.3 31.1 33.9Left, between crownsMAK-1/12 x x x 34.8 34.1 33.0 31.0 32.0

Minimum corpus breadthRight, at crownsMAK-1/12 21.6 x 20.9 19.6 18.2 18.8 20.8 RamusMAK-1/2 19.6 21.4 RamusRight, between crownsMAK-1/12 21.2 20.8 20.5 18.5 17.8 20.2 25.4MAK-1/2 20.2 23.6Left, at crownsMAK-1/12 21.4 20.5 20.6 18.6 17.2 18.6 20.3 RamusLeft, between crownsMAK-1/12 21.4 20.5 19.2 17.8 17.4 18.9 23.9

Various metrics, MAK-VP-1/12Bi-internal alveolar margin breadth:

I1, 4.6; I2, 11.6; C, 20.4; P3, 26.7; P4, 29.5; M1, 31.5; M2, (35 6 1); M3, (43 6 1)Bi-crown center breadth:

C, (30 6 1); P3, 35.8; P4, 38.0; M1, 42.0; M2, 44.4; M3, 50.3Maximum bicondylar breadth (118 6 2)Minimum bicondylar breadth 68.2Mental foramen height 1.9; 1.0 (R) (multiple); 1.6; 1.0 (L) (multiple)Mental foramen length 2.6; 1.0 (R) (multiple); 3.8; 1.3 (L) (multiple)Minimum height, base of mental foramen to basal contour 16.4 (R) (multiple); 15.3 (L) (multiple)Minimum height, base of mental foramen to alveolar margin 18.4 (RP4) (multiple); 19.1 (R) (multiple)Top condyle to basal plane (76 6 2) (R); (77 6 2) (L)Maximum mandibular length (120 6 2)Maximum condylar breadth (M-L) 31.7 (L)Maximum condylar length (A-P) (15) (L; pathological)Bi-mental foramen breadth (anterior edge) 40.3Height of condyle above occlusal plane (I1–M3) (47 6 2) (R); 42 (L)Various metrics, MAK-VP-1/2Minimum anteroposterior ramus length 52.4Height of condyle above occlusal plane (M2–3) (63 6 2)Various metrics, MAK-VP-1/83Minimum anteroposterior ramus length 58.61 All measurements are in millimeters and follow techniques outlined in White and Johanson (1982). Estimates are in parentheses.x, broken.


ies of A. afarensis microwear beyond those ofRyan and Johanson (1989), Greenfield(1990b), Puech et al. (1983, 1986), and Puechand Albertini (1983, 1984) are needed.

Enamel thickness can be measured ateither the occlusal surface or points of frac-ture (here limited to the cervical margins,far less informative about overall enamelthickness than measurements at the occlu-sal surface). Both the canine and the incisorlend themselves to occlusal surface measure-ment better than the molars. In molars,estimation of enamel thickness using occlu-sally exposed dentine is complex due touncertainty about the topography of thedentin-enamel junction and erosion of theenamel. The best way to measure molarenamel thickness is in broken or sectionedspecimens.

In the Maka right P4, the advanced wearallows assessments of coronal enamel thick-ness at the MB (1.7 mm) and DB (1.3 mm)corners of the crown. In the canine, thethickness along the labial face can be mea-sured near the crown apex cusp, where ithas a thickness of ,1.6 mm. The enamel issubstantially thinner on the lingual anddistal sides. Minor attrition has thinned theenamel somewhat at these locations. Chim-panzees in a limited sample do not exceed0.7–0.9 mm thickness in similar labial loca-tions. Humans characteristically haveenamel on the labial C surface of greaterthan 1 mm in a homologous location.

The significance of these enamel thick-ness values on the Maka and other A. afaren-sis specimens is that selection for increase inenamel thickness in the molars and premo-lars (the dietarily significant dimension) mayhave resulted in a systemic increase inenamel thickness in the anterior teeth. Thisis especially the case for the occlusal surfaceenamel.

Dentition: microscopicand developmental observations

Surface topography. The excellent pres-ervation and nearly full complement of per-manent teeth afford an opportunity to ad-dress issues of dental histology anddevelopment for the MAK-VP-1/12 speci-men. The teeth were examined by binocularmicroscope and the surface details by scan-ning electron microscopy (SEM) on epoxy

positives. There is a ‘‘stair-step’’ morphologyproduced by the flaking of enamel along theoutermost planes of the striae of Retzius(SOR). There is also minor erosion of thesurface, perhaps due to postdepositionaletching.

Perikymata were visible on all teeth. Theyexhibit the characteristic morphology of hu-man perikymata of an increasing densitytowards the cervical margin. No tooth yieldeda complete cusp to cervix count of periky-mata. Occlusal wear and polishing obliter-ated the most cuspal perikymata. Crownformation periods could not be estimatedusing this approach. The perikymata followan expectedly sinusoidal path in the cervicalareas.

In the lateral incisor, the perikymata den-sity increases from cusp to cervix, indicatinga slowing of growth as the cervix wasreached. This is similar to other A. afarensisteeth and contrasts with the regular cusp tocervix spacing seen in robust Australopithe-cus incisors (Bromage and Dean, 1985; Bey-non and Dean, 1988). For Maka, the densityof perikymata markedly increases per mmof height (10 per 1.4 mm to 10 per 1.0 mm) inthe area where the labial and lingual exten-sions bifurcate. This is also seen in L.H.-2(Beynon and Dean, 1988). This pattern sug-gests that modifications of the growth param-eters (especially duration) occur at the moredevelopmentally plastic cervical portionrather than at the cuspal portion (Simpsonet al., 1990; Simpson and Kunos, 1998; Reidet al., 1998a,b).

Pathology and development. The MAK-VP-1/12 dentition exhibits evidence of patho-logical growth. The RP4 has a macrochipwith rounded edges whose origin is indeter-minate. Like some other A. afarensis indi-viduals (Johanson et al., 1982b), the Makaspecimen has multiple enamel surface de-fects. The lateral incisor and the canine bothhave three major transverse surface defectson their labial enamel surfaces, each withmultiple identifiable perikymata in theirtroughs. The right M1 has a single, thin,cervically located band. Shallow transversestriae are also visible on the P4 and the othermolars.

Based on the number of perikymata ineach defect, it is possible that the most


cuspal defect on the Maka canine is a prod-uct of the same episode as the one locatedmost cervically on the lateral incisor. If weassume that this match is valid, the patternof dental growth in the Maka specimen maybe compared (Fig. 9) with developmentaldata from a large series of humans (n 5 422)and African apes (n 5 99) (Simpson et al.,1990, 1992; Simpson and Kunos, 1998).

MAK-VP-1/12 shows a reduced caninecrown and an earlier development of thecanine relative to the lateral incisor than inthe extant apes. The earlier, more progna-thic Australopithecus species, A. afarensisand A. africanus, are intermediate in theirpattern of dental development between theAfrican apes and the more orthognathichominids (A. robustus, A. boisei, H. sapiens).

Fig. 9. Bivariate comparison of the development ofthe mandibular canine and lateral incisor. On a scale of0.00–2.00, 0.00 equals no evidence of crown, 0.50 equalsenamel crown one-half complete, 1.00 equals crowncomplete with no root formation, etc. Open circles,

humans; gray squares, African apes; large open box,MAK-VP-1/12. Box includes full range of possibilities forregistering the hypoplastic bands. Note that the relativegrowth of the MAK-VP-1/12 canine is derived towards amore human ontogenetic pattern.


Not only had A. afarensis reduced the size ofthe canine, it also appears to have changedits relative ontogenetic pattern (Simpson etal., 1990, 1992). It appears that in A. afaren-sis the large canine no longer played acentral role in the acquisition or mainte-nance of social rank or reproductive success.(Johanson and White, 1979; Lovejoy, 1981).

The mandible

Previous comparative assessments of theA. afarensis mandible figured prominentlyin the recognition and systematic assess-ment of the taxon (Johanson et al., 1978;Johanson and White, 1979; White et al.,1981). The four new Maka specimens do notextend the mandibular size range of knownA. afarensis. The most complete, MAK-VP-1/12, is almost exactly the same size as theholotype L.H.-4 specimen (Table 2). Theramus fragment MAK-VP-1/83 is also anappropriate size match for these. The smallfragment MAK-VP-1/6 is at the small end ofthe A. afarensis range in corpus dimensionsat M2/M3. The largest of the Maka speci-mens, MAK-VP-1/2, is still considerablysmaller than the largest A. afarensis speci-mens from Hadar.

Bony morphology of all four specimens iswell within the established A. afarensisranges in all features (Figs. 10, 12, 13), butas for the teeth (Fig. 11), the completeness ofthe Maka specimens allows them to addvaluable information about that species.

Mandible corpus.Occlusal aspect. The overall shape of thedental arcade is almost exactly like A.L.400-1a and L.H.-4. The postcanine tooth rowis straight. Incisors and canines are verti-cally implanted in a tight arc, contrastingstrongly with the procumbent incisors ofmost African apes.

Lateral aspect. Both Maka specimensdeepen slightly anteriorly, as do most A.afarensis mandibles. The lateral promi-nence is difficult to assess in the MAK-VP-1/2 specimen, but is moderate in MAK-VP-1/12. This feature is highly variable in A.afarensis. The relative placement and mor-phology of the ramus root/corpus junction

was the most poorly understood area of theA. afarensis mandible prior to the new Makaspecimens. In a true lateral view, the ramiobscure the entire third molar crowns ofboth new specimens. This is very differentfrom the ape condition where the ramusarises more posteriorly, usually obscuringless of the third molar, even in the gorilla.This anteriorly arising, vertically orientedramus was indicated on the broken Hadaradults (except for A.L. 198-1) and was pre-saged by the immature 333-43 specimen.This young individual, with both deciduousmolars in place, shows that even early inontogeny the A. afarensis ramus was anteri-orly placed, large, and robust compared tothat of extant apes. In addition to the ante-rior position of the ramus root, a substantialextramolar sulcus (the anterior ramus edgeis set 13 lateral to the buccal anterior M3crown) is present on both Maka individuals.

A distinguishing feature of A. anamensisand A. afarensis mandibles is the lateralcorpus contour hollow, framed by the swol-len alveolar region above, by the root of theramus behind, and inferiorly by the basalmarginal torus sweeping upward to join theC/P3 root jugae antero-inferiorly. The men-tal foramen is usually set at the antero-inferior corner of this hollow, which varies indepth among described A. afarensis man-dibles. Both of the new Maka mandibles thatpreserve this area display this lateral corpuscontour hollowing. It is intact on both sidesof MAK-VP-1/2 where its extent, depth, anda-p elongate shape are near the A. afarensismean, approximating the hollows on theA.L. 198-1 and A.L. 400-1a specimens.

The mental foramen is multiple on bothsides of the MAK-VP-1/12 specimen. Asgauged perpendicular to the alveolar mar-gin of the P3–M1 series, the foramen iscentered below midcorpus at the P3/P4 posi-tion. As in most other A. afarensis speci-mens, the foramen opens antero-superiorly,toward the midcanine crown. A single acces-sory foramen is set midway between themajor mental foramen and the alveolar mar-gin on both sides, strongly recalling thesituation in L.H.-4.

As in other A. afarensis, the lateral toanterior corpus transition is accomplishedacross an even curve to which both the C and


P3 roots contribute. This is very differentfrom the condition in apes, where the caninejugum is the dominant, and often moreabrupt, turning point. Platysmatic striae

are seen on both Maka specimens, and thoseon MAK-VP-1/12 are similar to those on theHadar A.L. 288-1 mandible in prominence,orientation, and position.

Fig. 10. Mandibular corpus cross sections. Uppertwo rows are sections taken through casts at the firstmolar midcrowns, perpendicular to the lingual alveolarmargins. The lower sections were taken through themidlines, with the sections oriented relative to the

alveolar row. Broken portions and mental spines indi-cated by dotted lines. Note similarity of the Maka andLaetoli holotype specimens in shape and size, and theplacement of these individuals within the range of A.afarensis mandibles from Hadar.


Medial aspect. The alveolar prominence isnot marked in either specimen, and thebasal portion of the medial corpus is onlyweakly hollowed in the subalveolar region.This is a highly variable feature in A. afaren-sis. The disposition of the mylohyoid line isalso typical for A. afarensis on both Makaspecimens.

Anterior symphyseal region. In true lateralview, the angulation and shape of the mid-line profile of the mandible’s anterior sym-physeal region have come under recent scru-tiny with the announcement of two newspecies of Australopithecus (Leakey et al.,1995; Brunet et al., 1996). The range ofvariation in this feature in modern chimpan-zees is great, from a subvertical, flat alveo-lar region with a bulbous base, to moreevenly angled, posteriorly raking profiles.Similar variation is also seen in the gorilla.

The more vertically implanted the incisors,the more vertical the alveolar portion of thesymphysis tends to be. Variation in shapeand slant of this region is also substantialamong early hominids, ranging from theA.L. 288-1 specimen (fairly vertical, evenlyrounded) to the L.H.-4 mandible (superiorlyvertical, sharply sloping inferiorly, creatinga ‘‘bulbous’’ symphysis). The new Maka speci-men is similar to the A.L. 288-1 specimen inthese features (particularly in the subincisaljugae region), but at a larger size, and with aslightly more posterior slant. It is narrowerthan the A.L. 400-1a specimen, but its basalhalf does not slope as strongly posteriorly asdoes L.H.-4.

At the break between the alveolar andbasal portions of the midline contour thereis a low, rounded, palpable eminence thatoccupies the symphyseal tuber position. This

Fig. 11. Dental size and proportions in Australopithe-cus afarensis and Ardipithecus ramidus. All publishedspecimens from Hadar/Laetoli sufficient to show rela-tive dental proportions are depicted (specimens with atleast three measured canine or postcanine teeth). Notethat MAK-VP-1/12 has dental proportions typical for A.afarensis, and at midsize range. The Ardipithecus rami-dus dental set (White et al., 1994) shows small postca-

nines, especially P4 thru M3, and a relatively largecanine. Postcanine dimensions are the square root ofmeasured crown area, with estimates made allowing forpartial crown damage when appropriate. Measuredcrown areas were taken from Suwa (1990) and Suwa etal. (1994), or measured in the present study followingthe same methods. Canine dimension is buccolingualbreadth.


is similar to, but placed more inferiorlythan that seen in the L.H.-4 mandible.The basal incisura is not so marked as inL.H.-4 because the inferior anterior mar-ginal tubercles are not so prominently devel-oped.

Posterior symphyseal region. The postinci-sive planum of MAK-VP-1/12 is deeply hol-lowed, both transversely and supero-inferi-orly. This area is slightly narrower herethan in L.H.-4, but wider than in A.L. 288-1.It is very similar to what is seen in A.L.400-1a. The superior transverse torus andthe genioglossal fossa, whose superior bound-ary it forms, are developed in Maka to thesame extent as in L.H.-4. In true occlusalview the torus extends posteriorly to theanterior P4 position, as seen in most other A.afarensis specimens. The supraspinous fora-men of MAK-VP-12/1 perforates the floor ofthe genioglossal fossa, surmounting a verti-cal bony septum that bisects the fossa and iscontinuous inferiorly with a prominent,single bony spine. This differs from theL.H.-4 arrangement only in the narrownessand prominence of the single mental spine.The inferior transverse torus is similar in

size, shape, and disposition, but in the Laetolispecimen it extends more posteriorly rela-tive to the superior transverse torus becauseof the more receding nature of the basalportion of its symphyseal area.

Basal aspect. The basal aspect of the Makaspecimen is similar to that of A.L. 288-1 inshape. It is not so posteriorly everted as inthe L.H.-4 specimen, largely because of thelatter’s more posteriorly extending inferiortransverse torus. Digastric fossae are smalland shallow when compared to the extensivescalloping on the A.L. 400-1a base below theinferior transverse torus.

Mandible ramus.Lateral aspect. The three new Maka speci-mens confirm that the A. afarensis mandibu-lar ramus was vertically disposed, anteri-orly placed, tall, and robust compared tothat in chimpanzees. These features areapparent even in comparisons of very youngA. afarensis individuals (A.L. 333-43). TheMAK-VP-1/2 ramus is the largest, and is astall and wide as the large, very similar A.L.333-108 from Hadar. The coronoid process of

Fig. 12. Oblique view of the MAK-VP-1/12 (a) and the A.L. 288-1 (‘‘Lucy’’) (b) mandibles of A. afarensis.


MAK-VP-1/83 is very broad and similar tothe A.L. 333-100 specimen from Hadar in alldetails, including the lack of lateral flareand marked temporalis rugosity. The ecto-condyloid buttress is weak in all three speci-mens. There are very strong but brokenectoangular tuberculi on both MAK-VP-1/12and MAK-VP-1/2. Preserved portions of go-nial angle on both show that this part of theramus was fairly vertical and framed bythese masseteric attachments, neither in-verted nor everted, but with a moderatemasseteric fossa within the frame.

Medial aspect. The medial surface of theramus of both Maka specimens shows verylarge tuberosities for the medial pterygoidmuscles that encroach well onto the ramus.There is a deep excavation in the area of thetriangular planum on MAK-VP-1/2, similarto that seen on the A.L. 333-100 specimen.The MAK-VP-1/83 endocondyloid buttress ismore salient than the low but rugose endo-coronoid process. The former structure de-marcates the perpendicular transition fromthe area antero-inferior to the condyle to themedial surface of the ramus. The expansive

Fig. 13. Reconstructed mandibular bodies of themost complete mandibles from the three major A. afaren-sis sites. Top: Maka MAK-VP-1/12. Right: LaetoliL.H.-4. Left: Hadar A.L. 400-1a. Alignment of thespecimens in this nonstandard orientation facilitatescomparisons of dental size and arcade shapes. It is

difficult to find individuals whose dental arcades matchso closely in contemporary populations of African apes,lending strong support to the interpretation of A. afaren-sis as a single, ecologically and geographically wide-spread early hominid species.


surface between the Maka specimen’s endo-coronoid buttress and the anterior edge ofthe ramus is rugose, with the proportionsand relief in this region very similar to thoseseen in A.L. 333-100. The wide bony areaanterior to the buttress sets A. afarensisapart from extant apes. The retromolar fossais extensive in both Maka specimens,bounded laterally by the sharp ramus rootthat is already distinct at a vertical positionat the level of the alveolar margin. Themandibular foramen exits postero-superi-orly behind the retromolar fossae, into asulcus that extends nearly to the posteriorramus margin below the condyle.

Mandibular condyles. All three new Makaspecimens preserve portions of the condyle.

The MAK-VP-1/12 specimen is arthritic andis further described below. The MAK-VP-1/2condyle is broken in half, but was evidentlyin the midportion of the known A. afarensissize range. This condyle, as well as that ofMAK-VP-1/83, is very similar in articularcoverage and size to A.L. 333w-16.

Bony pathology

The only clearly pathological conditionseen on the new specimens involves themandibular condyles of MAK-VP-1/12. Thebetter-preserved left condyle shows severejoint degeneration, with a very rough, irregu-lar, pitted subchondral surface. This is theearliest bilateral temporomandibular jointdisease documented among hominids. It may

Fig. 14. Lateral radiographs of MAK-VP-1/12. Top: Right corpus. Bottom: Left corpus. Approximately naturalsize.


be the cause or consequence of the morpho-logical and occlusal wear asymmetries de-scribed above for this individual.

Radiography

Both MAK-VP-1/12 and MAK-VP-1/2specimens reveal subocclusal morphologyconsistent with previous descriptions of Ha-dar A. afarensis mandibles (Ward et al.,1982; Fig. 14). The mandibular canal can beseen to pass above the distal M3 root apex,curve downward to reach its lowest positionbelow M1, and then curve upward to reachthe mental foramen at the P3/P4 position.The distance between the M1 root apex andthe mandibular canal is greater in the MAK-VP-1/2 mandible, possibly related to themore heavily worn M1 crown and presumedcontinuous eruption. Of note are the double-rooted right and left P3’s with subequalmesial and distal root canal dimensions, andthe single-rooted P4 on both sides. The rootcanal is singular on the right P4, whereas asmaller distal canal furcation occurs on theleft side at midroot height.

DISCUSSION

The new specimens from Maka are verysimilar in all respects to the paratype seriesfrom Hadar and Laetoli. They do not signifi-cantly extend the known metric or morpho-logical ranges for this species, except per-haps in mandibular premolar root form.However, the preservation of the Maka man-dibles allows them to contribute signifi-cantly to systematic and functional consider-ations of A. afarensis.

The A. afarensis mandible

The mandible and its dentition playedcritical roles in the original description of A.afarensis. The Laetoli L.H.-4 specimen waschosen as the holotype of this taxon (Johan-son et al., 1978). Primitive dental and man-dibular characters were used to distinguishA. afarensis from other early hominids. Thefunctional dentognathic morphology of thisspecies, described as unique, has been fur-ther elucidated by additional discoveriesover the last 20 years, culminating with therecovery of a large adult male skull of thespecies that includes the largest known man-dible of A. afarensis (Kimbel et al., 1994).This discovery confirms earlier interpreta-

tions of the cranial morphology of the spe-cies (Kimbel et al., 1984).

The Maka MAK-VP-1/2 individual wasprobably a male, based on its position to-wards the large end of the overall speciesrange. The more complete but smaller MAK-VP-1/12 individual is nearer to the A. afaren-sis mean size, and its sex cannot be reliablydetermined. Descriptions of the large seriesof mandibles and teeth recovered from theslightly younger Hadar site to the immedi-ate north (Kimbel et al., 1994) will be crucialin clarifying the nature of mandibular anddental variation in this species.

With the discoveries of A. anamensis andA. ramidus, A. afarensis is no longer themost primitive fossil hominid. This newperspective is an important one for bothphylogenetic and functional studies.All threeof the new Maka mandibles reveal a primatewith a unique masticatory apparatus. A.afarensis differs from all extant apes and themore primitive Ardipithecus in the rela-tively small size of its canines, and itsrelatively large, thick-enamelled postcaninedentition. Relative to the chimpanzee, A.afarensis mandibles feature tall, verticallyoriented rami positioned anteriorly relativeto the dentition. Relative to the chimpanzee,A. afarensis mandible bodies are more ro-bust and the postcanine chewing platform isenlarged, with thicker enamel. This alreadymegadont taxon, and perhaps its closelyrelated temporal precursor A. anamensis,represent initial functional steps that wouldeventually culminate in the far more de-rived, specialized masticatory apparatus oflater hominid species, particularly A. boisei.

The A. afarensis canine/premolar complex

The C/P3 complex of A. afarensis lacks thefunctional honing seen in extant and extinctapes (Greenfield, 1990b). Prior to the recov-ery of MAK-VP-1/12, the best mandibularspecimen available to show the occlusalrelationships of the lateral incisor, canine,and third premolar was A.L. 400-1a fromHadar. However, the lateral incisor wear inA.L. 400-1a was unusual and the A.L. 198-1specimen lacked the incisor. The MAK-VP-1/12 Maka specimen, combined with evi-dence from other Hadar specimens, showsthat A. afarensis differs from the ape condi-tion in the arrangement and wear of these


three teeth and their maxillary counter-parts, confirming previous predictions byGreenfield (1990a,b, 1992). Gorilla incisorsare smaller and more vertically implantedthan those of chimpanzees, whose incisorstend to wear on the lingual surface ratherthan in a narrow, rectangular occlusal strip.Hominids have very vertically implanted,nonprocumbent incisors that wear from theincisal edge down toward the root. In adultapes, the incisal edges and the occlusal apexof P3 lie at a level well below the canine apex.In humans, the occlusal edge of the incisorsis on the same level as the C and P3 apices.The evolutionarily intermediate condition isbest exemplified by the MAK-VP-1/12 speci-men. Here, the incisal surface of the I2 is atthe same level as the anterior edge (mesialmarginal ridge) of the canine.

In A. afarensis, the functional incisal edgethus extends halfway across the lower ca-nine, whose anterior apex is blunted horizon-tally in early wear. Posteriorly, the lowercanine crown presents a sharply angleddisto-inferior slope down to the level of thepostcanine occlusal edge (midcrown P3). Thiscanine ‘‘rise’’ or ‘‘step’’ may function to pro-tect the third premolar and canine crownsfrom extreme wear in A. afarensis and conse-quently set up a steep wear gradient alongthe postcanine tooth row (White et al., 1981).This rise is present in younger individuals ofA. afarensis. Most old individuals of A.afarensis feature first molar crown wearexhaustion (A.L. 198-1, A.L. 311-1). TheM1–M3 wear gradient is extreme in theMAK-VP-1/2 specimen, a clear precursor tothese older individuals. Such strong gradi-ents are rarely seen in apes.

Early Australopithecus systematicsand evolution

Among the recurrent controversies sur-rounding the taxon A. afarensis are ques-tions regarding variation in the paratypeseries and pooling of the Laetoli and Hadarspecimens. These have been widely dis-cussed elsewhere, but the Maka discoveriesprovide a test of interpretations presentingA. afarensis as a single taxon (Johanson andWhite, 1979). The presence of both verylarge and very small specimens from a singlehorizon at Maka reinforces previous indica-tions of extensive size variation in this taxon

(Johanson and White, 1979). The close met-ric and morphological matches between theMAK-VP-1/12 specimen and the L.H.-4 holo-type of A. afarensis (Fig. 13) show that thistaxon was geographically widespread.

Within the context of the detailed anddominant mandibular and dental morpho-logical similarities between the Maka speci-mens and the pre-existing A. afarensis hy-podigm, particularly noteworthy is theoccurrence of a distinct root system in theMAK-VP-1/12 mandibular P3. Although two-rooted P3s have been previously known anddescribed for A. afarensis (White, 1977; Wardet al., 1982), it is only with the unambiguousobservation available for MAK-VP-1/12 thata partially molarized root form is recognizedto be part of the normal species range ofvariation. Structurally, this root pattern maybe associated with a relatively developedmesiolingual corner of the P3 crown, albeitwithin the normal A. afarensis ranges ofcrown variation, which differ significantlyfrom the ‘‘molarized,’’ ‘‘robust’’ Australopithe-cus condition.

Known A. afarensis mandibular P3 rootpolymorphism encompasses a wide range ofstructures. Some P3s exhibit the primitiveape pattern, consisting of a mesiobuccallyplaced relatively columnar root and a moreplate-like distal one (e.g., L.H.-4, A.L. 266-1). Within this category, the L.H.-24 P3possesses a distal root that is fully dividedinto buccal and lingual portions, thus effec-tively having three roots. Such a root pat-tern has recently featured prominently inthe ‘‘diagnosis’’ of ‘‘Australopithecus bahrel-ghazali’’ from Chad. Other A. afarensis speci-mens exhibit the structurally simplifiedTome’s root condition (e.g., L.H.-14, A.L.145-35), whereas MAK-VP-1/12 shows thepartially molarized root system, a conditionalso approximated by some Hadar speci-mens (cf. A.L. 333w-60). It is not surprisingthat a partially molarized P3 root system ispart of normal variation in A. afarensis, ataxon likely to be characterized by an en-hanced masticatory apparatus relative tothe ancestral hominid condition as dis-cussed above. We conclude that premolarroot form is highly polymorphic in A. afaren-sis, and that species-level diagnosis of earlyhominids should take such patterns ofwithin-species variation more fully into ac-


count (contra Wood, 1991, and Brunet et al.,1996).

What do the Maka discoveries have tocontribute to an understanding of the evolu-tionary relationships of the various earlyhominid species now recognized? The recog-nition of A. anamensis has shed new light onthe early evolution of Australopithecus. Rela-tive to the older Ardipithecus ramidus, A.anamensis shares with all later Australopi-thecus the derived character complex of thickmolar enamel and an enlarged postcaninedentition. The most persuasive characterused to distinguish A. anamensis from A.afarensis was the strong postero-inferiorinclination of the symphyseal region in theformer species (Leakey et al., 1995). TheLaetoli holotype of the latter species has aposteriorly angled anterior corpus regionrelative to many Hadar mandibles, and nowthe Maka counterparts. It may be temptingto argue for a gradual increase in symphy-seal steepness by seriating known man-dibles as follows: the KNM-KP-29281 man-dible (ca. 4.15 myr), the L.H.-4 mandible (ca.3.5 myr), and the new Maka mandible (3.4myr). The small sample sizes should, how-ever, give us pause, particularly when com-bined with observations of modern chimpan-zees. Here, the amount of variation betweenL.H.-4 and MAK-VP-1/12 or A.L. 400-1a(Fig. 10) can be matched in small (n 5 10,Cleveland Museum of Natural History)samples of modern chimpanzees. It is truethat the hominid symphysis became morevertical through time, but the rate at whichthis happened is still in the realm of conjec-ture, given the available samples.

We suggest that an appropriate samplewith which to test proposals of evolutionarystasis in A. afarensis (Johanson and White,1979; White et al., 1993) will be the enlargedHadar collection of teeth and mandibles.These specimens, spanning the 400,000years immediately postdating the Makasands, will provide a more robust test ofhypotheses concerning evolutionary modeand tempo than comparison of isolated fron-tal bones (Kimbel et al., 1994).

ACKNOWLEDGMENTS

Thanks go to the Ethiopian Centre forResearch and Conservation of Cultural Heri-tage, the Ethiopian Ministry of Information

and Culture, and the National Museum ofEthiopia for permission and support; to Dr.Tekelab Mekbib for radiographic assistance;to R. Kono-Takeuchi for preparing Figure14; to the Afar people of Gewane, Aramis,and Sagantole for field support; to Ato AlemuAdemassu for laboratory assistance; to J.D.Clark, Y. Beyene, and G. WoldeGabriel forleadership of the Middle Awash project; andto the following field workers for assistancein the 1990 work at Maka: J. DeHeinzelin, Y.Haile-Selassie, B. Latimer, K. Schick, S.Yirga, A. Negash, Z. Assefa, G. Hundie, W.K.Hart, and E. Vrba. We thank C.O. Lovejoy,D. DeGusta, H. Gilbert, three devoted re-viewers, and E. Szathmary for helpful com-ments on the manuscripts.

LITERATURE CITED

Asfaw B. 1987. The Belohdelie frontal: new evidence ofearly hominid cranial morphology from the Afar ofEthiopia. J Hum Evol 16:611–624.

Asfaw B. 1988. Pliocene cranial remains from Ethiopia:new perspectives on the evolution of the early hominidfrontal bone. Ph.D. dissertation, University of Califor-nia at Berkeley.

Beynon AD, Dean MC. 1988. Distinct dental develop-ment patterns in early fossil hominids. Nature 335:509–514.

Boaz NT. 1988. Status of Australopithecus afarensis.Yrbk Phys Anthropol 31:85–113.

Bromage T, Dean MC. 1985. Re-evaluation of the age atdeath of immature fossil hominids. Nature 317:525–527.

Brunet M, Beauvilain A, Coppens Y, Heintz E, MoutayeAHE, Pilbeam D. 1996. Australopithecus bahrel-ghazali, une nouvelle espece d’hominide ancien de laregion de Koro Toro (Tchad). C R Acad Sci [IIa]322:907–913.

Clark JD, Asfaw B, Assefa G, Harris JWK, Kurashina H,Walter RC, White TD, Williams MAJ. 1984. Paleoan-thropological discoveries in the Middle Awash Valley,Ethiopia. Nature 307:423–428.

Day MH, Leakey REF. 1973. New evidence of the genusHomo from East Rudolf, Kenya I. Am J Phys Anthro-pol 39:341–354.

Day MH, Leakey REF, Walker AC, Wood BA. 1976. Newhominids from East Turkana, Kenya. Am J PhysAnthropol 45:369–436.

Dirks W. 1998. Histological reconstruction of dentaldevelopment and age at death in a juvenile gibbon(Hylobates lar). J Hum Evol 35:411–426.

Goodman AH, Armelagos GJ. 1985. Factors affecting thedistribution of enamel hypoplasias within the humanpermanent dentition. Am J Phys Anthropol 68:479–493.

Greenfield LO. 1990a. Canine reduction in early man: acritique of three mechanical models. Hum Evol 5:213–226.

Greenfield LO. 1990b. Canine ‘‘honing’’ in Australopithe-cus afarensis. Am J Phys Anthropol 82:135–143.

Greenfield LO. 1992. Origin of the human canine: a newsolution to an old enigma. Yrbk Phys Anthropol35:153–185.

Johanson DC, White TD. 1979. A systematic assessmentof early African hominids. Science 202:321–330.


Johanson DC, White TD. Coppens Y. 1978. A new speciesof the genus Australopithecus (Primates: Hominidae)from the Pliocene of Eastern Africa. Kirtlandia 28:1–14.

Johanson DC, Taieb M, Coppens Y. 1982a. Pliocenehominids from the Hadar Formation, Ethiopia (1973–1977): stratigraphic, chronologic, and paleoenviron-mental contexts, with notes on hominid morphologyand systematics. Am J Phys Anthropol 57:373–402.

Johanson DC, White TD, Coppens Y. 1982b. Dentalremains from the Hadar Formation, Ethiopia: 1974–1977 collections. Am J Phys Anthropol 57:545–603.

Kay R, Grine FE. 1988. Tooth morphology, wear and dietin Australopithecus and Paranthropus from southernAfrica. In: Grine F, editor. Evolutionary history of the‘‘robust’’ australopithecines. New York:Aldine de Gruy-ter. p 427–447.

Kimbel WH, White TD, Johanson DC. 1984. Cranialmorphology of Australopithecus afarensis: a compara-tive study based on a composite reconstruction of theadult skull. Am J Phys Anthropol 64:337–388.

Kimbel WH, Johanson DC, Rak Y. 1994. The first skulland other new discoveries of Australopithecus afaren-sis at Hadar, Ethiopia. Nature 368:449–451.

Leakey MG, Feibel CS, McDougall I, Walker AC. 1995.New four-million-year-old hominid species from Ka-napoi and Allia Bay, Kenya. Nature 376:565–571.

Leakey RE, Walker AC. 1985. Further hominids fromthe Plio-Pleistocene of Koobi Fora, Kenya. Am J PhysAnthropol 67:135–163.

Leakey RE, Wood BA. 1973. New evidence of the genusHomo from East Rudolf, Kenya II. Am J Phys Anthro-pol 39:355–368.

Leakey RE, Mungai JM, Walker AC. 1971. New austra-lopithecines from East Rudolf, Kenya. Am J PhysAnthropol 67:135–163.

Lovejoy CO. 1981. The origin of man. Science 211:341–350.

Puech P, Albertini H. 1983. Usure des dents chezAustralopithecus afarensis: examen au microscope ducomplexe canine superieure/premiere inferieure. C RAcad Sci 296:1817–1822.

Puech P, Albertini H. 1984. Dental microwear andmechanisms in early hominids from Laetoli and Ha-dar. Am J Phys Anthropol 65:87–91.

Puech P, Cianfarani F, Albertini H. 1983. Tooth mi-crowear and dietary patterns in early hominids fromLaetoli, Hadar, and Olduvai. J Hum Evol 12:721–729.

Puech P, Cianfarani F, Albertini H. 1986. Dental mi-crowear features as an indicator of plant food in earlyhominids: a preliminary study of enamel. Hum Evol1:507–515.

Reid DJ, Schwartz GT, Dean C, Chandrasekera MS.1998a. A histological reconstruction of dental develop-ment in the common chimpanzee, Pan troglodytes. JHum Evol 35:427–448.

Reid DJ, Beynon AD, Ramirez-Rozzi FV. 1998b. Histo-logical reconstruction of dental development in fourindividuals from a medieval site in Picardie, France. JHum Evol 35:463–478.

Renne PR, WoldeGabriel G, Hart WK, Heiken G, WhiteTD. 1999. Chronostratigraphy of the Miocene-PlioceneSagantole Formation, Middle Awash Valley, Afar Rift,Ethiopia. Geol Soc Am Bull. 111:869–885.

Ryan AC, Johanson DC. 1989. Anterior dental mi-crowear in Australopithecus afarensis—comparisonswith human and nonhuman primates. J Hum Evol18:235–268.

Simpson SW, Kunos CA. 1998. A radiographic study ofthe development of the human mandibular dentition.J Hum Evol 35:479–505.

Simpson SW, Lovejoy CO, Meindl RS. 1990. Hominoiddental maturation. J Hum Evol 19:285–297.

Simpson SW, Lovejoy CO, Meindl RS. 1992. Furtherevidence on relative dental maturation and somaticdevelopmental rate in hominoids. Am J Phys Anthro-pol 87:29–38.

Suwa G. 1990. A comparative analysis of hominid dentalremains from the Shungura and Usno Formations,Omo Valley, Ethiopia. Ph.D. thesis, University ofCalifornia at Berkeley. 522 p.

Suwa G, Wood BA, White TD. 1994. Further analysis ofmandibular molar crown and cusp areas in Plioceneand early Pleistocene hominids. Am J Phys Anthropol93:401–426.

Suwa G, White TD, Howell FC. 1996. Mandibularpostcanine dentition from the Shungura Formation,Ethiopia—crown morphology, taxonomic allocations,and Plio-Pleistocene hominid evolution. Am J PhysAnthropol 101:247–282.

Walter RC, Aronson JL. 1993. Age and source of the SidiHakoma Tuff, Hadar Formation, Ethiopia. J HumEvol 25:229–240.

Ward SC, Johanson DC, Coppens Y. 1982. Subocclusalmorphology and alveolar process relationships of homi-nid gnathic elements from the Hadar Formation:1974–1977 collections. Am J Phys Anthropol 57:605–630.

White TD. 1977. New fossil hominids from Laetolil,Tanzania. Am J Phys Anthropol 46:197–230.

White TD. 1980. Additional fossil hominids from Laetoli,Tanzania. Am J Phys Anthropol 53:487–504.

White TD. 1984. Pliocene hominids from the MiddleAwash, Ethiopia. Courier Forschunginstitut Sencken-berg 69:57–68.

White TD. 1985. The hominids of Hadar and Laetoli: anelement-by-element comparison of the dental samples.In: Delson E, editor. Ancestors: the hard evidence.New York: Alan R. Liss. p 139–152.

White TD, Johanson DC. 1982. Pliocene hominid man-dibles from the Hadar Formation, Ethiopia: 1974–1977 collections. Am J Phys Anthropol 57:501–544.

White TD, Johanson DC, Kimbel W. 1981. Australopithe-cus africanus: its phyletic position reconsidered. S AfrJ Sci 77:445–470.

White TD, Suwa G, Hart WK, Walter RC, WoldeGabrielG, de Heinzelin J, Clark JD, Asfaw B, Vrba E. 1993.New discoveries of Australopithecus at Maka, Ethio-pia. Nature 366:261–265.

White TD, Suwa G, Asfaw B. 1994. Australopithecusramidus, a new species of early hominid from Aramis,Ethiopia. Nature 371:306–312.

White TD, Suwa G,Asfaw B. 1995. Corrigendum: Austra-lopithecus ramidus, a new species of early hominidfrom Aramis, Ethiopia. Nature 375:88.

WoldeGabriel G, White TD, Suwa G, Renne P, deHeinzelin J, Hart WK, Heiken G. 1994. Ecological andtemporal placement of early Pliocene hominids atAramis, Ethiopia. Nature 371:330–333.

WoldeGabriel G, Renne P, White TD, Suwa G, deHeinze-lin J, Hart WK, Heiken G. 1995. Age of early hominids.Nature 376:559.

Wood BA. 1991. Koobi Fora research project. Volume 4.Hominid cranial remains. Oxford: Clarendon Press.466 p.

Wood BA, Abbott S, Uytterschaut HT. 1988. Analysis ofthe dental morphology of Plio-Pleistocene hominids.IV. Mandibular postcanine root morphology. J Anat156:107–139.


jaws and teeth ofaustralopithecus afarensis from maka, middle awash, ethiopia

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