CALIFORNIA STATE UNIVERSITY, NORTHRIDGE

VALIDITY OF THE SPECIES:

Australopithecus afarensis

A thesis submitted in partial satisfaction of the requirements for the degree of Master of Arts in

Anthropology

by

James Braxton

May, 1983 The Thesis of James Braxton is approved:

California State University, Northridge

ii ACKNOWLEDGEMENTS

I wish to thank the following people for their support and

guidance. First, the members of my committee. Second, my

family for their generous support, ideas, and allowing me the time to complete my endless obsession. Finally, to

Nancy Murray who generously donated her time, her computer expertise, and for solving my constant program errors.

iii TABLE OF CONTENTS

Acknowledgements • iii

List of Tables vi

List of Figures vii

Abstract • viii

CHAPTER

I. INTRODUCTION 1

II. LITERATURE REVIEW • 4

Biostratigraphical and Geochronological Evidence 4

Osteological Remains 7

Morphological Characteristics • 10

Jaw and Dental Characteristics 10

Cranial Characteristics • 14

Postcranial Morphology 15

Biological Species Concept 17

The International Code of Zoological Nomenclature and the Taxonomic Status of Hadar-Laetoli Fossils .• 17

Summary • 20

iv Table of Contents (continued)

II I. MATERIALS AND METHODS 22

Materials--Fossil Hominid Sample • 22

Comparative Sample • 25

Measurement Data • 28

Methods 28

Univariate Analysis 31

Multivariate Analysis 31

Fossil Hominid Sample 32

IV. RESULTS • 34

Univariate Analysis Histograms: Fossil Hominid Sample Variation 34

Multivariate Analysis: Fossil Hominid Sample 41

Canonical Variate Analysis 48

Summary of Results 50

v. DISCUSSION 55

Morphological Characteristics • 55

International Code of Zoological Nomenclature • 56

Geographic Isolation 57

Statistical Implication • 58

VI. CONCLUSION 61

Literature Cited • 64

v LIST OF TABLES

Table Page

1. Comparison Between A.afarensis and later Australopithecus and Early Homo • • • • • • • • 11

2. Fossil Hominid Specimens Included in the Analysis and their Geologic Origin • • • • . . . 23 3. Taxonomic Assignments of the Fossil Hominid Specimens • • • • • • • • • • • • • • • • 26 4. Fossil Hominid Sample Data - Maxillary Dentition . . . . 29 5. Fossil Hominid Sample Data - Mandibular Dentition . . . 30 6. Fossil Hominid Sample Data • ...... 33 7. Principal Component Analysis -Maxillary Dentition • 42

8. Principal Component Analysis - Mandibular Dentition 43

9. Principal Component Scores - Maxillary Dentition • • 44

10. Principal Component Scores - Mandibular Dentition 46

11. F Test of Mahalanobis D2 -Maxillary and Mandibular Dentitions • • • • • • ...... 49 12. Jackknifed Classification - Maxillary and Mandibular Dentitions • • • • • • • • • ...... 53

vi LIST OF FIGURES

Figure Page

1. Geological Column of the Hadar Formation Histograms 6

2. Maxillary Dentition - Canine . . . . 35 3. Maxillary Dentition - p3 ...... 36

4. Maxillary Dentition - Ml 37

5. Mandibular Dentition - Canine 38

6. Mandibular Dentition - P3 39

7. Mandibular Dentition - M1 40

8. Bivariate Plot of Principal Component Scores - Maxillary Dentition • • • • • • • • • • • • . . . . . 45 9. Bivariate Plot of Principal Component Scores - Mandibular Dentition •••••••••••• . . . . . 47 10. Bivariate Plot of Canonical Variate Analysis - Maxillary Dentition • • • • • • • • • • • • . . . . . 51 11. Bivariate Plot of Canonical Variate Analysis - Mandibular Dentition • • • • • • • • • • • • . . . . . 52

vii ABSTRACT

VALIDITY OF THE SPECIES:

Australopithecus afarensis

by

James Braxton

Master of Arts in Anthropology

This thesis is an attempt to test the hypothesis that Austra­ lopithecus afarensis is not significantly different from any other

Plio-Pleistocene hominid. This problem is of interest to anthro­ pologists because corroborating the hypothesis of the proposed taxon

A.afarensis has important implications for interpretations of early hominid phylogeny. Analyses of fossil material from Hadar and Laetoli suggest the following: 1) A.afarensis is the earliest known bipedal hominid, 2) the extreme degree of morphological variation exhibited by A.afarensis can most likely be attributed to sexual dimorphism

(rather than the Hadar-Laetoli fossils representing more than one species), and 3) controversy over the taxon A.afarensis has caused a reinterpretation of early hominid evolution. The validity of the proposed species, A.afarensis, was evaluated by a critical review of

viii the literature and statistical analyses of dental measurements of a representative sample of Pliocene and Pleistocene hominids. Uni­ variate and multivariate statistical methods were utilized to compare the variability exhibited by A.afarensis with that of the Fossil

Hominid sample. The results of these analyses suggest that A. afarensis is a valid taxon.

ix CHAPTER I

INTRODUCTION

Fossil remains of the Pliocene and Pleistocene hominids that represent the genus Australopithecus show considerable geographical, temporal, and morphological variation. Interpretation of these vari­ ations has led to many hypotheses, such as those proposed by: 1)

Wolpoff (1973) and Brace (1979), who state that sexual dimorphism within one species can account for the known morphological variation exhibited by the genus Australopithecus, 2) Walker and Leakey (1978) who hypothesized that more than one species evolved, such that dif­ ferent australopithecene species may have been contemporaneous both in time and space, and 3) Robinson (1963), whose dietary hypothesis suggests that several genera may have co-existed simultaneously.

Plio-Pleistocene sites from Eastern and Southern Africa have yielded fossil material for many hominids and among these remains, several australopithecine forms have been discovered. Australopithe­ cus africanus remains may be represented at Lake Turkana, Kenya, and

Omo, Ethiopia, as well as the South African sites of Makapansgat and

Sterkfontein (Howell, 1969; Leakey, 1978; Wolpoff (1971). However,

Cronin et al. (1981) doubt the existence of A.africanus in the East

African geographic area. Fossil material for A.boisei comes from

Olduvai Gorge, Tanzania, and Omo, Ethiopia. Fossil remains for Aus­ tralopithecus robustus come from Lake Turkana, Kenya, as well as the

1 2

South African sites of Kromdraai and Swartkrans (Leakey, 1978;

Wolpoff, 1971). These East and South African deposits represent time

spans of 3.0 million to 1.5 million years for hominids finds (Howell,

1969; Leakey, 1966; Leakey, 1972; Tobias, 1976).

Fossil remains of the proposed hominid Australopithecus afarensis

were found at two Pliocene sites in East Africa (subsequent use of the

name A.afarensis is for descriptive purposes only and not an advocated

position). These sites are Hadar, Ethiopia, and Laetoli, Tanzania, whose hominid yielding deposits are dated between 3.65 and 4.2 million years (Johanson et al., 1978; Leakey et al., 1976).

Interpreting the features of the fossil material for A.afarensis,

Johanson and White (1979:325-327) suggest that dental, cranial, and

postcranial characteristics show considerable differences from pre­ viously known Plio-Pleistocene hominids. Such features include:

1) large canines that project beyond the tooth row, 2) a diastema that interrupts the tooth row between the lateral incisors and 3 canines, 3) a C/P3 cutting complex, 4) sectorial P3 's, 5) P 's with two and sometimes three distinct roots, and 6) alveolar prognathism.

Furthermore, fossil remains from Hadar and Laetoli are interpreted by

Johanson (1980) to represent a new form of early hominid which is characterized by size variation, most likely due to sexual dimorphism.

To test the null hypothesis that A.afarensis is not significantly different from all other Plio-Pleistocene hominids, the following points will be examined: 1) biostratigraphical and geochronological evidence, 2) current concepts on A.afarensis' taxonomic status, 3) anatomical comparisons between A.afarensis and other known australo­ pithecines, and 4) biometric analyses of dental measurements for 3

~.afarensis and a representative sample of Pliocene and Pleistocene

hominids. The validity of Weinert's classification of the Garusi I

specimen as Meganthropus africanus will also be discussed (Johanson,

1980). Therefore, it is the purpose of this paper to test the null

hypothesis that Australopithecus afarensis is not significantly

different from any other Plio-Pleistocene hominid. The alternate

hypothesis is that ~.afarensis is significantly different from all

other known Plio-Pleistocene hominids. The paramount issue is whether the morphological differences between A.afarensis and other

Plio-Pleistocene hominids are sufficient to justify a separate

taxonomic classification for A.afarensis.

Characteristics of the cranial, dental, and postcranial morphology can be used to ascertain the taxonomic status of fossil material. Teeth, either isolated or associated with other fossil material, along with mandibles and maxillae, represent the majority

of fossil hominid remains from Pliocene and Pleistocene deposits.

Dental morphology has proved to be invaluable when making taxonomic

distinction between australopithecine species (Robindon and Steudel,

1973).

To analyze dental variation, statistical (biometric) procedures were performed on measurements from a representative sample of

Pliocene and Pleistocene hominids. Results from these statistical analyses were used to test the null hypothesis. CHAPTER II

LITERATURE REVIEW

The collection of fossil remains of the proposed hominid

Australopithecus afarensis comes from two known Pliocene sites in

Eastern Africa. These sites are Hadar, Ethiopia (11N, 40 30E) and

Laetoli, Tanzania (3 128, 35 11E) which have been dated between 3.65

and 4.2 million years old (Aronson et al., 1977; Johanson et al.,

1982; Leakey~ al., 1976; Walter and Aronson, 1982). The similar­

ities between fossil remains at Laetoli and Hadar suggest that these

remains may represent a single taxon according to Johanson (1980).

Although fossil remains for A.ararensis come from two East African

sites, the majority of hominid material is from Hadar, Ethiopia.

Laetoli Hominid-4 (LH 4) was selected by Johanson (1980) as the

holotype (a single specimen designated as "the type" for a new

species or subspecies in the original description) for both locations

because: 1) its morphology is characteristic of the species and 2)

it has been previously described and illustrated (Johanson, 1980;

White, 1977).

A. Biostratigraphical and Geochronological Evidence

The Afar sedimentary basis, which is approximately 150 km long

and 60 km wide, is located in a depression at the northern end of the

East African rift valley and is dated to Plio-Pleistocene age (Taieb

et al., 1976:289). A considerable amount of this basin is capped by

4 5

Pleistocene sand and gravel, with the underlying Pliocene strata being termed the Central Afar Group. The Central Afar Group can be further subdivided into a number of sequences including Amado, Gewane,

Gueraru, Hadar, Haouna, Leadu, and the Meschelle. It is the Hadar formation including the Kada Hadar (KH Member), Denen Dora (DD Mem- her), Sidi Hakoma (SH Member), and the Basal Members (see Figure 1), totaling about 140 meters of the deposits which has produced the known hominid material of the Afar region (Taieb et al., 1976).

The majority of fossils collected at Hadar have been surface finds; however, small-scale excavations have uncovered in situ materials

(Johanson and Taieb, 1978). Hominid remains have generally been located within two members: 1) the Sidi Hakoma Member, about 40 meters above the basalt flow, and 2) the Denen Dora Member, approx- imately 40 meters below the basalt flow (Johanson and Taieb, 1978).

Information gathered from these two stratigraphic layers was analyzed so that an accurate date could be provided.

Initial isotopic dating (K-Ar decay, utilizing "an extraction system with an 38Ar spike pipette and a MS-10 mass spectrometer") performed on the SHT tuff, located about 15 meters below the marker bed, proved to be inconclusive when three out of the five tests pro- duced dates which were inconsistent (this was later attributed to use of "weathered" tuff in the analyses) with a range of values between

3.1-5.3 Myr ± 0.03 Myr (Taieb et al., 1976:292).

Faunal material such as fossil remains of pigs and elephants played an important role in establishing an accurate date for the

Hadar formation. Cooke's (1978) sequence of several pig lineages, which span nearly four million years of evolution, provided evidence 6

Figure 1

Geological column of the Hadar Forma.tion

rv ..... ~-'-- BKT 3 '>I vvvv_v>~ ·.~·.;·"lt•'~··/:t~ 2.88 f0.08 m.y. (K/Ar) BKT 2 .; V;tv .( v "".J 2.70 ~.20 m.y. (fission track) KH MEMBER

'I';;,,, •; ,• •'•: ~:: BKT 1 vVVVV ""' ,. ·.·~ •11:~1·' cc :§@@, KHT """"~~ 162 DD MEMBER DD-3 J!:~~·:~o;:.;,•:; *188 *241, 333

DD-2 .!•• ~.~-~ *366, 58 *161

TT 2-3 ~v vv vv'lv.J *207 TT 1 Y VVI/ Vl/v'J *211, 322 Basalt ~ 3.65 +0.15 m.y. (K/Ar) *266 - SH MEMBER Gastropods T.·7·'1"r-v,... v t.:;> ;...<.;_ v *311 --v-~ .~~~.·tJ,:,~!: *228 SH-3 •• " t' .. •' ~ ...... - • ""' • "i *277, 400, 411 '- SH-2 .,,•.;.(.·t~ *137, 166 *128, 129, 145 SHT 2 "" V'i o,Jv'l/ *198, 199, 200, 249 BASAL MEMBER SHT 1 vi/'V'\1 -l'lV ~-~·-l.-P c - ----,

* Fossil remains of the Hadar Formation

From: Johanson, Taieb, and Coppens (1982:390) 7

that the original 3.0 Myr basalt date was too young. Additional K-Ar tests on pure basalt samples collected from the Sidi Hakoma Member during the 1976-1977 field session produced dates of 3.75 million years± 0.10 Myr (Aronson~ al., 1977; Walter and Aronson, 1982).

This new date now shows that the Hadar and Laetoli fossil material, which are nearly identical in morphology, are also nearly identical in age (Johanson and White, 1979).

Finally, in addition to K-Ar tests, geomagnetic analyses were performed on the basalt flow to determine its polarity. Paleomagnetic analysis is accomplished by studying the magnetic crystals in rocks and charting the position of their polarity (normal = North Pole positive and South Pole negative; the reverse is considered abnormal).

Tests conducted by Schmitt and Aronson (1977) indicate that the basalt layer probably was formed during the Gilbert reversal period, some 3.4 to 4.2 million years ago.

B. Osteological Remains

The first significant fragmentary fossil evidence for Australo­ pithecus afarensis, according to Johanson and White (1979), was dis­ covered at Garusi, Tanzania, in 1939 by Kohl-Larsen. The remains consist of a maxillary fragment with both upper premolars and a well preserved alveolus (socket) for a canine tooth (Kohl-Larsen, 1943).

The first Ethiopian fossil evidence was discovered at Hadar in

1973. These remains consisted of four associated leg bones (right and left proximal femora and a right proximal tibia and distal femur; labeled as A1 128, 129) which were located in a mudstone deposit, the

Sidi Hakoma Member (Johanson and Taieb, 1976). 8

The 1974 Hadar field work produced considerable hominid and mammalian discoveries, including a partial skeleton of a female hom­

inid found in the KHT stratum member and labeled AL 288-I (Johanson

and Taieb, 1978). This fossil hominid specimen was given the name

"Lucy" and is the most complete Pliocene fossil hominid specimen

(with approximately 40% of the skeleton recovered) known to date

(Johanson and Edey, 1981).

Fossil material for the species A.afarensis characteristically has "strong dimorphism in body size" and a high degree of robusticity

in respect to muscle and tendon insertions when compared to the known fossil material for the genus Australopithecus (Johanson et at.,

1978:7). Analyses of the pelvis, femur, tibia, and patella have produced evidence that A.afarensis was well adapted to bipedal loco­ motion (Johanson et al., 1976; Lovejoy, 1974). However, Stern and

Susman (1982) suggest that the postcranial material from Hadar

indicates locomotor abilities which may have included a significant amount of arboreal activity. From this postcranial material, it appears that Australopithecus afarensis had well developed powerful peroneal muscles. Both the peroneus longus and brevis are instru­ mental in extending and everting the foot (Stern and Susman, 1982;

Lovejoy, 1974). The powerful peroneal muscles, in conjunction with:

1) curvature of the pedal and manual phalanges, 2) orientation of the scapular glenoid, and 3) a high humerofemora index, support Stern and

Susman's proposal that A.afarensis was capable of arboreal activity.

Furthermore, they suggest that ~.afarensis possessed a method of transferring weight from the hip to the front of the foot which was different from that of modern H.sapiens. They cite the following 9

evidence to support this contention: 1) the articular surface of the acetabulum lacks a pubic contribution, 2) several Laetoli footprints lack an impression for the ball of the hallux, and 3) the variable length of the lateral toe relative to the length of the hallux. Fur­ ther evidence for bipedal locomotion was found in footprints left in volcanic ash at Laetoli, nearly four million years ago. Leakey and her research team (1979) strongly suggest that these footprints were left by a bipedal hominid walking through wet volcanic ash. The pelvis of A.afarensis resembles corresponding fossil material for

Sts 14 found at the South African site of Sterkfontein (Johanson and

Taieb, 1976:296).

Finally, associated paleontological evidence indicates that a lake was present at Hadar some three to four million years ago (Gray,

1979). Environmental conditions of the lake and the river(s) that supplied it were important to the australopithecines. The lake mar­ gins probably supplied food and certainly supplied water but at the same time these regions were most likely dangerous for early hominids.

Predators such as lions and leopards probably stalked A.afarensis at the lake's edge but danger extended beyond the simple predator to the elements themselves, in the form of flash floods. Certain hominid remains located at Hadar may represent either a family unit (fossil site AL 333) or at least a cohesive unit of adults and children.

Although the AL 333 site had fossil remains for both sexes and represents age groups from infant to adult, the exact number of individuals represented at this site is uncertain (Johanson, 1976;

Johanson and Edey, 1981). 10

C. Morphological Characteristics

One method for assessing the validity of the species A.afarensis

is to compare dental characteristics between A.afarensis with those

of later australopithecines and specimens of early Homo (see Table 1;

from Greenfield, 1980:356-357). This table clearly illustrates that

A.afarensis does indeed exhibit primitive dental characteristics when

compared to later australopithecines and specimens of early Homo.

Finally, a more detailed analyses of dental characteristics displayed

by A.afarensis, later australopithecines, and early members of the

genus Homo (the Plio-Pleistocene hominid sample) can be found in

Chapter 3.

Morphological characteristics which Johanson and co-workers

consider distinctive for A.afarensis are discussed next.

D. Jaw and Dental Characteristics

Mandibles of the Hadar-Laetoli specimens are variable in size

and are moderately thick dimensionally. These specimens have a

rounded, evenly curved symphysis. In the Hadar specimens the sym­

physis is characterized by having two internal transverse tori which

extend across the medial face of the symphysis (Johanson and White,

1979). A slight variation exists between Hadar and Laetoli hominids,

relative to the length of the mandibular transverse tori (Johanson

~ al., 1978). At the Hadar site, the two transverse tori are: 1)

nearly identical in length, 2) rounded in configuration, and 3) less

shelf-like in appearance than the Laetoli fossil remains. Laetoli

hominid remains are identified by a single lower transverse torus

which is shelf-like in appearance and extends further to the rear of Table 1

Comparison between A.afarensis and later Australopithecus and early Homo

A.afarensis later Australopithecus and early Homo

Incisors a. Relative size X = 26 (N=l) X = 18 OR 12-21 (N=5)

(11 area) b. Angle of r1 projection X = 60° (N=1) X = 72° OR 69-77° (N=4)

C/P3 Complex Maxilla: combined sexes Maxilla: combined sexes a. Relative size X = 67 OR 61-77 (N=5) X = 48 OR 33-73 (N=14)

(C 1 area) M 1 area Mandible: combined sexes Mandible: combined sexes

X = 53 OR 45-68 (N=3) X = 41 OR 24.63 (N=22) b. Canine projection Both sexes, slight projection, Both sexes, crown tip reduced reduction of crown tip to cheek to cheek tooth occlusal plane tooth occlusal plane delayed rapidly compared to A.afarensis c. Canine interlock and Early interlock with P3 and other Rare interlock, little or no wear canine, eventual loss of interlock shear, tip blunted with reduction of canine's height, shear, and blunting

1-' 1-' Table 1 (continued)

A.afarensis later Australopithecus and early Homo d. Diastemata (crown) Variable in size between r2 Rarely seen - except in some and cl early Homo e. Canine dimorphism Primarily metric two sizes Primarily metric two sizes f. P3 morphology Sectorial with major and minor cusps, Multi-cusped, round blunting elongate and less oval, early shear only but followed rapidly by blunting g. P3 orientation 45-60° orientation with tooth row Not angled in most specimens

P3/P4 heteromorphy Intermediate-extreme Slight-none p3 morphology Triangular or rectangular, buccal Rectangular face broader than lingual, some mesial edge concavity

Tooth Rows Primarily straight some curve Most curved medially, elongated medially, V-shaped or elongate parabola or parabola some square parabola, general shape long anteriorly, general shape shorter and narrow and broader than A.afarensis

Zygomatic insertion Primarily Ml and MlfM2 Primarily p4fMl, Ml and MlfM2

DM1 morphology Molarized premolar some honing Molariform wear, raised trigonid

Source: Greenfield (1980:356-357)

...... N 13

the symphysis than do the Hadar specimens (Johanson and White, 1979;

Johanson et al., 1978). It has a subrectangular shape and a diastema interrupts the tooth row between the lateral incisors and canines, in

AL 200-Ia and b (Johanson and White, 1979; Johanson et al., 1978).

The central incisors of A.afarensis are characterized by a large mesio-distal length while the lateral incisors of A.afarensis are reduced in size (Johanson et al., 197 8).

Australopithecus afarensis is characterized by variation in canine size and form which can be attributed to sexual dimorphism, according to Johanson and White (1979). The canines for both "sexes" project beyond the occlusal level of the adjacent teeth and the canine roots are long and massive, extending well into both upper and lower jaws. Wolpoff (1979) suggests that the wear facet which exists on the distal-lingual face of the upper canine and the associated exposed dentin of the P3 were caused by a C/P3 dental cutting complex.

White (1981) disagrees with Wolpoff's interpretation since supporting evidence is confined to the occlusal wear facets on the right P3 of

LH-14. Instead, White suggests that rotation of the P3's crown caused a malocclusion with the upper canine and p4, and this resulted in the unique wear facets described by Wolpoff.

The postcanine teeth of A.afarensis are generally large, and are broader buccal-lingually than mesial-distally (Johanson and White,

1979).

Premolar teeth normally are comprised of a dominant mesio­ distally elongated buccal cusp. The usual configuration of the occlusal outline is that of an elongated oval. The P3 orientation is "mesio-buccal to disto-lingual at an angle of between 45 to 60 14

degrees to the mesio-distal axis of the tooth row" (see Table 1) which is not typical of most specimens of later australopithecines or

Homo (Johanson and White, 1979:322). The lower third premolar (P3) often has two separate roots, while the upper third premolar (p3) sometimes has three distinct roots (Johanson and White, 1979). The 3 P3 is a sectorial tooth and the P is usually a little larger than the fourth upper premolar (p4) (Johanson and Edey, 1981). The fourth premolar does not exhibit "mesio-distal elongation of the buccal crown" area (Johanson and White, 1979:322).

Lower molars are characteristically squared in outline and "the cusps are arranged in a simple Y-5 pattern" (Johanson and White,

1979:322). This is observed in the M1 and M2 teeth and the usual molar size sequence is M3-M2-M1 (Johanson and White, 1979; Johanson etal., 1978).

E. Cranial Characteristics

The adult specimens of A.afarensis exhibit: 1) strong alveolar prognathism, 2) procumbent incisors, 3) widely flaring zygomatic arches, 4) shallow palate, and 5) a compound temporal-nuchal crest which is characterized by strong muscle marking (see Table 1)

(Johanson et al., 1978). In addition, the mastoid process is large and the external auditory meatus is tubular in shape (similar to pongids) from a basal perspective (Johanson and White, 1979). Cranial estimates for Australopithecus afarensis are between 380 and 450 cubic centimeters (Kimbel and White, 1980). These estimates are within the known range of cranial capacity for chimpanzees (320-475 cc) as well 15 I· as gracile (428-500 cc) and robust (500-530 cc) australopithecines

(Holloway, 1978:387).

F. Postcranial Morphology

The Hadar-Laetoli specimens exhibit both "strong sexual dimorphism in body size" and a high degree of skeletal robusticity with "regards to muscle and tendon insertions" (Johanson et al.,

1978:7).

The Hadar hand bones are different from those of modern humans in several respects (although the South African site of Sterkfontein has produced fossils with similar characteristics): 1) the capitate is "waisted," 2) the third metacrapal lacks a styloid process, and

3) the "phalanges are curved longitudinally" (Johanson and White,

1979:324).

The pelvis of Australopithecus afarensis (AL 288-I) has an elongated shape (as compared to those of the pongids) when viewed from the transverse plane with an anterior-posterior orientation.

Furthermore, Lovejoy (1980) suggests that broadening of the pelvic basis, as reflected by the breadth of the pelvic inlets, in

A.afarensis was necessary to support the lower viscera during upright stance. This allows for efficient bipedalism, but not the birth of large-headed infants (Lovejoy, 1980).

Observations made by Johanson and co-workers on the A.afarensis os coxae indicate the presence of the following: 1) broadened ilium, posterior extension of the iliac crest, and the position and orien­ tation of the ischial tuberosity with respect to the acetabulum, which closely resemble those features associated with hominids, 16

2) strongly developed anterior spines (inferior and superior) which have straight anterior margins, 3) shallow acetabulum compared to that of Homo sapiens and the fossil specimen Sts 14 (A.africanus), and 4) presence of a distinct greater sciatic notch (Johanson and

White, 1979; Johanson et al., 1978). Furthermore, both the ilium and ischium are short in length, relative to their respective widths

(Lovejoy, 197 4).

The morphology of the femur (AL 128, 129, and 288-I) resembles that for modern humans (Johanson et al., 1976). These characteristics include: 1) large bicondylar angle, 2) deep groove on the patella with a high lateral ridge, and 3) an anterioposteriorly elongated lateral condyle which also is characterized by a flattened articular surface (Johanson and Taieb, 1978). The knee joint of A.afarensis has the following hominid characteristics: 1) an oval shape of the patella and 2) both knees meet at the midline of the body. These morphological characteristics indicate that A.afarensis was adapted to bipedal walking (Lovejoy, 1974, 1980).

Leakey (1979) has examined the foot bones and footprints left in wet volcanic tuff at Laetoli and concluded that A.afarensis had a foot similar to that of modern man. However, Leakey and her research team failed to specify exactly which tests were performed. The

A.afarensis foot had a longitudinal arch similar to that of Homo sapiens, curved foot phalanges, and a hallux (great toe) which showed no indication of divergence from the other toes (Johanson and White,

1979; Leakey and Hay, 1979). 17

G. Biological Species Concept

From new phyletic material, taxonomic status must be determined according to the principles of Systematic Zoology or, more specifi­ cally, to the strict interpretations of the International Code of

Zoological Nomenclature. Furthermore, the fundamental taxon incor­ porated within the Linnaean hierarchy of Systematic Zoology is the biological species.

A biological species as defined by paleontologists is an objec­ tive, nonarbitrary group of populations, which are reproductively isolated from other such groups (Mayr, 1969; Simons, 1967). Further­ more, species are populations composed of animals, not "types," which exhibit different degrees of variability. A definition of a species should stress its distinctness rather than its differences (Buettner­

Janusch, 1973). Moreover, the genotype (the genetic constitution of a taxon) of the population is the fundamental element in speciation, and mutually exclusive geographical ranges, producing reproductive isolation, are the prerequisite for this process to occur (Buettner­

Janusch, 1973). Finally, this definition of a biological species allows for potential evolutionary change to occur without endangering the integrity of the species.

H. The International Code of Zoological Nomenclature

and the Taxonomic Status of Hadar-Laetoli Fossils

Johanson and White (1979) have concluded that A.afarensis, the oldest and most primitive hominid (apart from Ramapithecus) that can be substantiated by the fossil record be considered the basal hominid. In their taxonomic scheme, A.africanus is considered at an 18

intermediate stage of development between A.afarensis and A.robustus.

Moreover, they do not consider A.africanus to be ancestral to Homo.

Objections to Johanson and White's taxonomic scheme have been voiced by several paleoanthropologists including Brace, Day, Mary and

Richard Leakey, Olson, Walker and Wolpoff. The Leakeys, along with

Day, Olson and Walker, disagree with Johanson and White's interpreta­ tions of the International Code of Zoological Nomenclature as well as their classification of the Hadar and Laetoli fossil material as

Australopithecus afarensis (Day et al., 1980; Leakey and Walker,

1980). Day et al. (1980) suggest that Johanson and White violated certain articles of the International Code of Zoological Nomenclature, particularly Numbers 53, 74a, and 74e, when they proposed the new species, Australopithecus afarensis. Leakey and Day state that

Johanson and White have incorrectly designated one Laetoli hominid

(LH 4) as a holotype, which violates Article 74a, instead of using the correct term of lectotype (Day et al., 1980). Day and co-workers further state that Article 74e is violated by including the Garusi I

"Meganthropus africanus" specimen in the type-series of A.afarensis.

Listing "Meganthropus africanus" as an outmoded systematic name had the effect of making A.afarensis a replacement name for Weinert's

M.africanus, which is thought to be in violation of Article 53 (Day et al. , 1980).

According to strict interpretation of the International Code of

Zoological Nomenclature, Weinert did not satisfy Article 13a(i) because he failed to include a diagnostic statement by which

"Meganthropus africanus" can be differentiated from all other known taxa (Johanson, 1980; Mayr, 1969). After prolonged studies of the 19

Garusi I remains, Remane (1951) proposed the following list of its diagnostic characteristics: 1) three rooted p3, 2) enamel extension on the buccal face of the p3, and 3) large and projecting canines.

Remane firmly supported Weinert's classification of the Garusi I specimen and stated that its premolar construction resembled that of the pongids more than that of the known hominids (Remane, 1954).

Other paleoanthropologists, including Robinson (1953), Tobias

(1965), and Pilbeam (1972), doubt the close affinity between the

Garusi I specimen "Meganthropus africanus" and the Meganthropus II mandible from Java "Meganthropus paleojavanicus". Robinson (1953) stated that M.africanus should be considered an an australopithecine which is more closely related to the South African specimens than to

·~.paleojavanicus". Tobias (1965) and Pilbeam (1972) think that the

Garusi I specimen represents a gracile australopithecine.

Therefore, since Weinert failed to substantiate his taxon M. africanus, it must be considered an invalid binomen (Johanson, 1980).

As a result, two implications are indicated: 1) A.afarensis cannot be considered a junior homonyn of A.africanus and 2) Johanson did not violate Article 53 of the International Code of Zoological

Nomenclature.

Finally, Johanson and White (1979) followed the International

Code of Zoological Nomenclature when: 1) proposing the new species

A.afarensis and 2) satisfying Articles 13a(i) and 72 and Recommenda­ tions 73B and 73C; therefore, no violation of Article 74a or 74e occurred.

Richard Leakey's comments have varied from stating that A. afarensis was not ancestral to Homo to claiming that A.afarensis 20

has Homo characteristics and should be considered a member of that genus (Leakey and Lewis, 1977; Leakey and Walker, 1980).

Wolpoff (1981) and Brace (1979) contend that A.afarensis resem­ bles !·africanus too closely to be considered a separate species.

They suggest that morphological differences due to dramatic sexual dimorphism can account for the variation seen in the fossil material for A.afarensis and should not be considered taxonomically signifi­ cant from !·africanus (Brace, 1979; Wolpoff, 1980).

Kennedy (1979) challenges the validity of A.afarensis on the basis of its morphological distinctiveness, and cites inconsistencies in Johanson's list of primitive features for A.afarensis as support.

Characteristics such as large, projecting canines, the "waisted" appearance of the capitate, and a lack of a styloid process on the third metacarpel, can be seen in gracile australopithecine fossil remains from the South African site of Sterkfontein. Finally, she states that the cusps of the anterior premolars and orientation of the tooth row in A.afarensis are similar to the dental morphology seen in the Miocene hominid Ramapithecus.

Summary

Johanson and White have stated that fossil specimens recovered from Laetoli and Hadar exhibit primitive characteristics in dental, cranial, and postcranial material when compared to the known fossil remains for the genus Australopithecus (Johanson and White, 1979;

Johanson et al., 1978). Primitive dental characteristics of the

Hadar~Laetoli fossils include the following: 1) large projecting canines, 2) canine/premolar dental cutting complex, and 3) diastema 21

between the canines and the lateral incisors. Hadar-Laetoli fossil remains also provide evidence of bipedalism as indicated by analyses conducted on postcranial material at Hadar and on footprints preserved at Laetoli. Furthermore, Johanson and White have suggested that the fossil material from Laetoli and Hadar represent a new species of

Australopithecus: A.afarensis (Johanson and White, 1979).

Support for Johanson and White's classification of the Hadar and

Laetoli material as Australopithecus afarensis can be substantiated by the following: Articles 13a(i) and 72 and Recommendations 73B and

73C of The International Code of Zoological Nomenclature. Australo­ pithecus afarensis appears therefore, to represent the oldest and most primitive hominid that can be substantiated by the fossil record.

Validity of the proposed species Australopithecus afarensis has been challenged by paleoanthropologists including Brace, Day, the

Leakeys, Kennedy, Olson, Walker, and Wolpoff. The Leakeys, along with Day, Olson and Walker suggest that Johanson and White incorrectly assigned Laetoli hominid (LH 4) as the holotype and violated Articles

53, 74a and 74e of The International Code of Zoological Nomenclature, when the proposed the new species Australopithecus afarensis (Day et al., 1980; Leakey and Walker, 1980). Brace (1979) and Wolpoff (1980) suggest that once sexual dimorphism is considered, there is little significant difference between A.afarensis and A.africanus. Finally,

Kennedy (1979) suggests that primitive features (such as large, pro­ jecting canines, and the "waisted" appearance of the capitate) asso­ ciated with A.afarensis can also be found in fossil remains of A. africanus from Sterkfontein. CHAPTER III

MATERIAL AND METHODS

The purpose for analyzing the Fossil Hominid sample was to ascertain if the proposed species A.afarensis is significantly dif­ ferent from other species of the genus Australopithecus. The fossil specimens and the statistical methods used in this study are described in this chapter. The validity (testing of the null hypothesis) of the proposed species A.afarensis was partially evaluated by statistical analysis of dental measurements of a representative sample of Pliocene and Pleistocene hominids (Fossil Hominid sample). Mandibular and max­ illary dental measurements of these Plio-Pleistocene hominids were evaluated by univariate and multivariate statistical methods to com­ pare the variability exhibited by !•afarensis with that of the Plio­

Pleistocene hominid sample.

Material

A. Fossil Hominid Sample

Table 2 lists the geologic origins of the specimens in the Fossil

Hominid sample. Each fossil specimen is identified by its museum accession number and accompanied by the following: 1) its strati­ graphic position and 2) an estimate of its geologic age. Three spec­ imens, one from each of the three sites at Hadar, Ethiopia, were included in the analysis. The sites are located in the Sidi Hakoma member. Five specimens are from four sites in the Ileret and Koobi

22 23

Table 2

Fossil Hominid Specimens Included in the

Analysis and Their Geologic Origin

Specimen Local Stratigraphy Age (my) Source

East African Sites Afar

AL 199-1 Hadar Formation, Sidi Hakoma member 3.6 3 AL 200-1a Hadar Formation, Sidi Hakoma member 3.6 3 AL 266-1 Hadar Formation, Sidi Hakoma member 3.6 3

Lake Turkana

ER 729 Ileret, below middle tuff 1.6-1.8 5 ER 992 Ileret, below Chari tuff 1.4-1.6 5 ER 1590 Lower member Koobi Fora Formation, 1.9-2.3 5 below the KBS tuff ER 1802 Lower member Koobi Fora Formation, 1.9-2.3 5 below the KBS tuff ER 1813 Upper member Koobi Fora Formation 1.57 5

Laetoli

Garusi I Laetolil Beds 3.6 4 LH 3 Laetolil Beds 3.6 4 LH 4 Laetolil Beds between Aeolian 3.6-3.7 4 tuff b and c

Olduvai Gorge

OR 5 Surface FLK, Bed 1 1.7-2.1 1 OR 7 FLK NN; middle Bed 2 1.75 1

Lake Natron

Nat ron Peninj lacustrine facies 1.5 2

South African Sites Kromdraai

TM 1512 Kromdraai B (Late Swartkrans 1.5-2.0 7,8 Faunal Span) TM 1517 Kromdraai B (Late Swartkrans 1.5-2.0 7,8 Faunal Span) TM 1600 Kromdraai B (Late Swartkrans 1.5-2.0 7,8 Faunal Span) 24

Table 2 (continued)

Specimen Local Stratigraphy Age (my) Source

Makapansgat

MLD 2 Gray Breccia (Phase 1 Breccia) 3.0 6,7 MLD 18 Gray Breccia (Phase 1 Breccia) 3.0 6,7 MLD 40 Gray Breccia (Phase 1 Breccia) 3.0 6,7

Sterkfontein

STS 7 Limestone Breccia 2.5 7,8 STS 17 Limestone Breccia 2.5 7,8 STS 52 Limestone Breccia 2.5 7,8 STS 55 Limestone Breccia 2.5 7,8

Swartkrans

SK 13 Pink Breccia 2.0-2.6 6,7 SK 23 Pink Breccia 2.0-2.6 6,7 SK 27 Pink Breccia 2.0-2.6 6,7 SK 46 Pink Breccia 2.0-2.6 6,7 SK 48 Pink Breccia 2.0-2.6 6,7 SK 55 Pink Breccia 2.0-2.6 6,7

List of Sources: 1. Hay (1976) 2. Isaac and Curtis (1974) 3. Johanson and Taieb (1976) 4. Leakey et al. (197 6) 5. Leakey (1978) 6. Partridge (197 3) 7. To bias (1976) 8. Vrba (1975) 25

Fora formations, east of Lake Turkana, Kenya. Temporal limits for these sites are 1.4 to 2.3 million years BP (Leakey, 1978). Three specimens are from sites located in the Laetoli Beds, Tanzania, which are dated between 3.6-3.75 million years BP (Leakey et al., 1976).

Two specimens come from Bed I Olduvai Gorge, Tanzania. Dating for the base of Bed I is from 1.7-2.1 million years BP (Hay, 1976).

The Lake Natron (Peninj) specimen has been dated at approxi­ mately 1.5 million years BP (Isaac and Curtis, 1974).

The South African site of Kromdraai is represented by three specimens. Tobias (1976) and Vrba (1975) have stated that the hominid bearing breccia of Kromdraai is 1.5-2.0 million years old. Three hom­ inid fossil specimens come from Makapansgat, the majority of which are associated with the Phase I Breccia (gray breccia) which is dated at approximately 3.0 million years BP (Partridge, 1973; Tobias, 1976).

Four hominid specimens come from Sterkfontein breccia which is dated at approximately 2.5 million years old (Tobias, 1976; Vrba, 1975).

Finally, six hominid specimens come from the "pink breccia" of

Swartkrans, which is dated by Partridge (1973) and Tobias (1976) as being between 2.0-2.6 million years BP.

B. Comparative Samples

The sample of Pliocene-Pleistocene fossil hominid specimens has the composition described as follows:

Australopithecines. Data on twenty-seven Australopithecus specimens (!.africanus, A.robustus, and A.boisei; see Table 3 for taxonomic assignments) were selected from Johanson and Taieb (1976),

Leakey (1978), White (1977), and Wolpoff (1971). Only specimens with 26

Table 3

Taxonomic Assignments of the

Fossil Hominid Specimens

Specimen Classification Source

East African Sites

Afar

AL 199-I Australopithecus afarensis 1

AL 200-Ia Australopithecus afarensis 1

AL 266-I Australopithecus afarensis 1'

Lake Turkana

ER 729 Australopithecus robust us 2

ER 992 Homo habilis 2

ER 1590 Homo habilis 2

ER 1802 Australopithecus robustus 2

ER 1813 Australopithecus africanus 2

Laetoli

Garusi I Australopithecus afarensis 3

LH 3 Australopithecus afarensis 3

LH 4 Australopithecus afarensis 3

Olduvai Gorge

OH 5 Australopithecus boise! 4

OH 7 Homo habilis 4

Lake Natron

Natron AustraloEithecus boisei 4 27

Table 3 (continued)

Specimen Classification Source

Kromdraii

TM 1512 Australopithecus robustus 4

TM 1517 Australopithecus robustus 4

TM 1600 Australopithecus robust us 4

Makapansgat

MLD 2 Australopithecus africanus 4

MLD 18 Australopithecus africanus 4

MLD 40 Australopithecus africanus 4

Sterkfontein

STS 7 Australopithecus africanus 4

STS 17 Australopithecus africanus 4

STS 52 Australopithecus africanus 4

STS 55 Australopithecus africanus 4

Swartkrans

SK 13 Australopithecus robustus 4

SK 23 Australopithecus robustus 4

SK 46 Australopithecus robustus 4

SK 48 Australopithecus robustus 4

SK 55 Australopithecus robustus 4

List of sources:

1. Johanson and Taieb (1976) 2. Leakey (1978) ·3. White (1977) 4. Wolpoff (1971) 28

data on the mandibular and maxillary canine, first premolar, and first molar teeth were selected as suggested by Johanson (Johanson and Edey, 1981:276). The Fossil Hominid sample represents several geographic regions, although not all are equally represented.

Homo. Data on three Homo habilis specimens were also taken from

Leakey (1978) and Wolpoff (1971). These specimens have been classi­ fied as belonging to the taxon Homo habilis (OH 7 is considered the type specimen) following the arguments set forth by Leakey et al.

(1964).

C. Measurement Data

Data for each specimen were gained from measurements of mesio­ distal and bucco-lingual crown diameters of the upper (C, p3 and M1) and lower (~, P3 and M1) dentitions. Table 4 presents data for the

Fossil Hominid sample with a key to the sources of data.

Data was obtained from the aforementioned primary sources, as funding was unavailable for personal examination of the original fossil specimens.

D. Methods

The mandibular and maxillary dental measurement data were anal­ yzed by using univariate and multivariate statistical methods. Uni­ variate statistical analyses were performed to describe variability within the Fossil Hominid sample. Multivariate statistical analysis of the Fossil Hominid sample dealt with among-group variability.

Finally, these statistical analyses were performed to determine the 29

Table 4

Fossil Hominid Sample Data

Maxillary Dentition

Dimension (mm) c p3 M1 Specimen (L) (B) (L) (B) (L) (B) Source

AL 199-1 (1) 8.70 9.30 7.30 11.20 10.10 12.00

AL 200-1a (1) 9.40 10.95 8.95 12.10 11.80 13.15

ER 1590 (2) 11.35 12.35 10.15 13.45 13.40 13.90

ER 1813 (2) 8.10 8.40 8.00 11.10 12.20 12.50

LH 3 (3) 11.60 12.50 8.90 13.40 12.90 14.60

OH 5 (4) 8.75 9.80 10.90 17.00 15.20 17.70

Natron (4) 7.35 8.20 16.25 16.00

TM 1512 (4) 8.80 9.40 8.90 11.90 12.00 13.60

TM 1517 (4) 10.10 13.70 13.70 14.60

STS 17 (4) 8.70 12.90 11.45 13.40

STS 52 (4) 9.85 9.80 8.65 12.80 12.25 14.05

STS 55 (4) 9.10 13.90

SK 13 (4) 9.75 13.15 13.40 14.90

SK 27 (4) 10.60 10.40 9.50 13.40 14.00 13.20

SK 46 (4) 8.30 13.20 11.90 15.20

SK 48 (4) 8.20 8.80 9.20 13.70 13.10 14.00

SK 55 (4) 8.25 8.75 9.50 13.30 14.50 14.40

List of sources: 1) Johanson and Taieb (197 6); 2) Leakey (1978); 3) White (1977); 4) Wolpoff (1971). 30

Table 5

Fossil Hominid Sample Data

Mandibular Dentition

Dimension (mm) c p3 M1 Specimen (L) (B) (L) (B) (L) (B) Source

AL 266-1 (1) 9.15 10.10 12.10 11.95

ER 729 (2) 8.50 10.00 12.00 13.00 15.50 15.50

ER 992 (2) 9.15 8.70 9.35 11.15 11.95 10.80

ER 1802 (2) 10.40 12.10 14.65 13.20

Garusi I (4) 10.10 11.70 14.80 13.60

LH 3 (3) 11.70 10.40 12.60 10.60 13.40 13.30

LH 4 (3) 10.30 10.00 11.85 12.60

OR 7 (4) 9.05 9.05 9.60 10.20 14.30 12.30

Natron (4) 7.35 8.20 9.55 13.50 16.25 15.40

TM 1517 (4) 9.95 11.50 14.40 13.00

TM 1600 (4) 9.80 12.20 13.50 13.20

MLD 2 (4) 10.75 13.50 14.80 13.85

MLD 18 (4) 9.00 10.50 10.00 12.20 11.60 13.00

MLD 40 (4) 8.30 9.50 10.00 11.00 12.80 12.30

STS 7 (4) 9.20 11.00 8.50 12.00 12.00 12.70

STS 52 (4) 9.10 10.00 9.00 11.70 13.20 12.90

SK 23 (4) 7.95 7.90 9.50 11.45 14.75 14.65

SK 55 (4) 9.60 11.00 14.35 13.70

List of sources: 1) Johanson and Taieb (1976); 2) Leakey (1978); 3) White (1977); 4) Wolpoff (1971).

' ~ 31

phenetic relationships that exist between the Hadar-Laetoli specimens

and members of the Fossil Hominid sample.

E. Univariate Analysis

In the univariate analysis, histograms were utilized to describe within-group variability of the fossil hominids.

The histograms were constructed as follows: 1) the complete

Fossil Hominid sample (see Table 3) was used, 2) dental measurements

(both mandibular and maxillary) were utilized per fossil hominid, and

3) measurements were taken from the following teeth: the canine,

first premolar, and first molar. Histogram distributions of dental measurements should indicate the presence or absence of bimodality.

Bimodality may be due to sexual dimorphism, species, or generic dif­

ferences between A.afarensis and members of the Fossil Hominid sample.

F. Multivariate Analysis

Principal component and canonical variate analyses were used to describe the patterns of variation in the measurements and specimens

included in the Fossil Hominid sample.

Principal component analysis of the Fossil Hominid sample was

based on a variance-covariance matrix. These statistical tests were performed using BMDP4M (Dixon and Brown, 1979). Principal component analysis seeks to explain the total variance (common variance plus unique variance) for each variable using the smallest number of com­ ponents as possible. In this analysis of dental measurements, prin­ cipal component (variance-covariance) analysis was used to provide

1) new uncorrelated variable sets and 2) to identify patterns of 32

relationships among the specimens within the Fossil Hominid sample

(Oxnard, 1973).

Canonical variate analysis was performed using BMDP7M (Dixon and

Brown, 1979). Variables used within this analysis "to compute linear classification functions are selected in a stepwise manner" (Dixon and Brown, 1979:711). Also, canonical variate analysis identifies variables which maximize between-group variance relative to within­ group variance. Finally, in respect to this study, the most important aspect of the analysis produced by BMDP7M is the Mahalanobis' D2 statistic, the measure of generalized distance which is tested using the F-statistic (Dixon and Brown, 1979).

G. Fossil Hominid Sample

The Fossil Hominid Sample is actually comprised of sub-samples of specimens: those represented by the maxillary dentition and those represented by the mandibular dentition. Analyses were conducted on either maxillary or mandibular dentitions using only specimens that had data for the canine, first premolar, and first molar.

Table 6 summarizes the following information: 1) the number of complete specimens (those containing dental measurements for the canine, first premolar, and first molar), 2) the total number of specimens used per sample, and 3) the frequency of missing dental data. 33

Table 6

Fossil Hominid Sample Data

Sample Number of Total Number of Complete Population Specimens Specimens

Maxillary 18 10

Mandibular 17 11

Frequency of Missing Teeth

Sample Population c p3 M1

Maxillary 6 (2 9. 41%) 1 (5.55%) 1 (5.55%)

Mandibular 8 (44.44%) 0 0 CHAPTER IV

RESULTS

The results obtained from univariate and multivariate methods described in Chapter 3 will be discussed in this chapter.

Univariate Analysis

A. Histograms: Fossil Hominid Sample Variation

Within-group variability exhibited by the Fossil Hominid sample was demonstrated by the use of histograms. Histograms are divided into these categories: 1) jaw type (either maxillary or mandibular) and 2) type of dental measurements analyzed (mesio-distal or bucca­ lingual measurements). Twelve histograms (see Figures 2-7) were con­ structed following the criteria outlined in Chapter 3. Each increment on the abscissa represents 0.5 standard deviation unit, while the ordinate represents the number of specimens in the sample.

All histograms exhibit some degree of deviation from normality.

Bimodal distributions can be seen in the following histograms: 1) the bucca-lingual distribution for the maxillary canine (Figure 2),

2) the mesio-distal distribution for the M1 (Figure 4) and 3) the mesio-distal distribution for the M1 (Figure 7). The following histograms best illustrate normal distributions: 1) mesio-distal distribution for the maxillary canine (Figure 2) and 2) bucca-lingual distribution for the P3 (Figure 6).

34 35

Figure 2 Histogram folaxillary Dentition Canine Mesio-Distal

4

3

Ul c .....~ 2 u c.. tf)"' .... ~ 1 SK 55 'I'M 1512 STS 52 SK 27 "' SK 48 0!15 IAL 200-I ER 1590 "' ER 1813 ~ Peninj AL 199- Ul3 I - -1 .o -. 5 0 :> 1.0 1.5 2.0 Standard Deviation Units

Bucca-Lingual

., 3 E"'" ..<., o." l~ .... 2 0 '· .D 'I'M 1512 E"' £ 1 STS 52 - Peninj SK 55 ER 1590 0!1 5 ER 1813 SK 48 SK 27 AL 2Cl0-l Ul) AL 199-

1.5 I; - -1.0 -• 5 0 .5 1.0 1.5 2.0 Standard Dev:<.ation units 36

Figure 3 Histogram Maxillary Dentition p3 Mesio-Distal 5

~ , ....E" 8. : 2 I"" 15~ 0 .,.. ~55 .Q ~17 5I: 55 ~ 1 S'lS52 pl:3 SI:4S '111 1517 SX46 ~2~1:. SI 27 AL 199-I Ja 1813 sz: 13 IR 1590 OH5

-1.0 1.0 2.0 2.5

Buc_c o-Lingual ·j 7

6

5

4

3 '1'1( 1517 c "., Sl: 55 ....B u "8. 51:48 ...Ul 2 SX46 ..0 SI 27 0 .Q 5I: 13 :z:3 1 ER 181:3 TK 1512 S'l'S 52 Lll3 IAL 199-I i4L 200Ia S'l'S 17 Ell. 1813 S'l'S 55 OH5 -;; -1.5 -1.0 -· 0 . 1.0 1.$ 2•0 2.5 J,U Standard DeviatiDn Unite 37

Figure 4 Histogram Maxillary Dentition Ml Mesio-Distal

4

:; .,~ ~ tJ

~ 2 ...0 .. 'DI 1512 'DI 1511 .r>"' !i S'l'S 52 SK 48 S'l'S 11 sz: 1 I SK46 Ul.3 S( 13 S( 55 AL 199-I At. 200...11 Ef\_1813 m 1590 S( 21 Cll5 PcWlj

~.o -1.0 1.0 "2.0

Bucc6-Lingual

4

., :; "tJ ~ ' "~ VJ ... 2 0 ..., 'DI 1512 .J!, E S'l'S 17 S'1'S 52_ 'DI 1511 sz: l " SI 27. SI4S St. 55 SI..r.6 AL 199-! ER 1813 AL 200...:t ER 1590 LP..3 SK 1.3 Psninj C!l5

I -II -.2.0 -·5 0 ·5 1.0 2.0 :;.o St.an

Figure 5 Histogram Mandibular Dentition Canine Mesio-Distal

:1

., .,r:: 3 $, "~ If) 2 ...0 .,... S'1'S 52 .t:J S'1'S 7 ~ 1 Cll7 Sl23 KLD 18 Peninj 11LD 40 :m 7.l9 :m 992 Ul3

-.5 2..0

Bucca-Lingual

... ..0 II .t:J J 1 OH7 S'l'S52 KLD 18 SK 23 Per.inj :rn 992 KLD 40 ER 729 Ul3 S'l57

I . ..:a.o -·5 0 1.0 2.0 Standard Deviation Unit.e 39

Figure 6 Histogram Mandibular Dentition p3 Mesio-Distal

. -

".,c: ~ 8. "' '1'M 1600 HLD 4D ..0 ...., iii 1517 m.D 18 St 2.) S1 55 Guuai-, ..~ 1 S'1'S 52 Ell 992- Pemnj BR 11!02 srs '7 AL 26£,..; Cl!? Ul4 IIIJl 2 BR '729 IB3

-1.5 -1.0 -. 0 ·5 1.0 115 .2.b 2.5 ).0

Bucco-Lingual ·

4

..c: 3 c; ...E 0 .,t. 2 ...c ... .! S'rS52 ~ liE l . Sl 55 'IM 1517 S'1'S 7 01!7 MLD lS S!; 2.) Garus:i-'I ~ 1600 hn1nj LRJ.. Al 199-! I.E) 1m 992 ER 1802 MLD 2 ER "129 HLD 4D

' ' -2.0 ·l.5 -1.0 -.5 0 l.O 1.5 2.0 Standard Deviation llr.its 40

Figure 7 Histogram Mandibular Dentition Ml Mesio-Distal

4

., :; f ~.., & "' 2 ...0 STS 7 7!! 1517 .,.. IIUl 18 512.3 .&> ~ L1!4 TM 1~00 JW) 2 IC 1 ~ER992 S'l'S52 St 55 Garu.si- AI. 2~ l'.LD AD I.!!3 Cll7 ER 1802 1CR"I'29 Ptminj I I -1.5 -1.0 -.5 0 . "1.0 1.5 2.0

Bucca-Lingual

s

:-

., ! ~ ...... ,

l.... 2 ..0 '1M 1600 1! n! 1517 OH7 STS52 i 1 Sl 55 KLD 18 STS7 Garusi- Peninj ER 992 AL 266-I U!4 !!l.D 2 IJ!3 MLD 40 SK 23 ER '729

-2.5 -2.0 -1.5 -1.0 -., 1.0 1.5 2.0 St.anciard Deviation Unite 41

These histogram distributions also illustrate the relative

position of the Hadar-Laetoli specimens with respect to other members of the Fossil Hominid sample. In the majority of these distributions,

Australopithecus afarensis specimens are associated with the gracile hominids more often than they are with the robust forms. Finally,

the apparent variability exhibited by the Fossil Hominid sample may be explained by the presence of: 1) sexual dimorphism, 2) species, or generic differences.

Multivariate Analysis

B. Fossil Hominid Sample: Among-group Relationships

Tables 7 and 8 present the following information obtained from the principal component analysis for the maxillary and mandibular dentition: 1) eigenvalues, 2) the percent of variance explained by each principal component, and 3) cumulative percent of variance.

Tables 7 and 8 show that the first component accounts for nearly 62.5 and 54 percent of variance, respectively, for these analyses. Fur­ thermore, all variables in Table 7 but not in Table 8 exhibit high positive loading for the first component, which is an indication that most of the variance is probably size-related.

Further analysis of the Fossil Hominid sample was achieved through the use of bivariate plots of the principal component scores to identify patterns of relationships among the specimens within the

Fossil Hominid sample. The abscissa (horizontal axis) of the bivari­ ate plots (see Tables 9 and 10 for data used to produce Figures 8 and

9) represents Principal Component 1, while the ordinate (vertical axis) represents Principal Component 2. Figures 8 and 9 illustrate 42

Table 7

Principal Component Analysis

Maxillary Dentition

Principal Component Variables 1 2 3 4 5 6

1 Canine Length 0.38 1.16 0.13 0.10 0.23 -0.053

2 Canine Breadth 0.43 1.22 -0.13 -0.16 -0.20 0.028

3 p3 Length 0.94 0.034 0.20 0.35 -0.16 0.021

4 p3 Breadth 1.49 -0.21 -0.21 -0.034 0.10 0.23

5 M1 Length 1.20 -0.27 0.53 -0.21 -0.0055 -0.053

6 M1 Breadth 1.33 -0.28 -0.38 0.0027 0.0044 -0.22

Eigenvalue 6.65 3.02 0.54 0.20 0.13 0.11

Percent of Variance 62.48 28.38 5.06 1.88 1.19 1.01

Cumulative Percent of Variance 62.48 90.86 95.92 97.80 98.99 100.00 43

Table 8

Principal Component Analysis

Mandibular Dentition

Principal Component Variables 1 2 3 4 5 6

1 Canine Length -0.66 0.87 -0.12 -0.24 0.26 0.032

2 Canine Breadth -0.50 0.52 0.67 -0.23 -0.19 -0.13

3 p3 Length 0.30 1.20 -0.16 0.35 -0.073 -0.035

4 p3 Breadth 0.68 -0.16 0.70 0.18 0.22 -0.14

5 M1 Length 1.49 0.10 -0.43 -0.22 -0.007 -0.21

6 M1 Breadth 1. 38 0.31 0.34 -0.12 -0.027 0.27

Eigenvalue 5.36 2.57 1.28 0.33 0.16 0.15

Percent of Variance 54.42 26.12 12.95 3.36 1.60 1. 55

Cumulative Percent of Variance 54.42 80.55 93.49 96.85 98.45 100.00 44

Table 9

Principal Component Scores

Maxillary Dentition

Principal Component Specimen PC 1 PC 2 PC 3 PC 4 PC 5 PC 6

AL 199-I -1.58 -0.02 -1.91 -0.51 -0.48 1.12

AL 200-Ia -0.44 0.70 -0.83 0.94 1.64 0.04

ER-1590 0.65 1.64 0.35 1.36 0.72 0.25

ER 1813 -1.12 -0.83 0.42 -0.13 -0.40 -0.93

LH 3 0.53 1.80 -0.10 -1.30 -0.34 -1.00

OH 5 2.32 -1.13 -0.15 0.23 0.18 0.20

SK 27 0.84 0.57 1.52 0.34 -1.30 1.53

SK 48 0.13 -1.01 -0.10 0.46 -0.04 1.40

SK 55 0.41 -1.14 1.63 0.30 0.11 -0.94

STS 52 -0.10 0.15 -0.70 -0.42 -1.72 -0.60

TM 1512 -0.52 -0.29 -0.74 0.93 -0.02 -1.50 45

Figure g Bivariate Plot of Principal Component Scores Maxillary Dentition

SK 27 AL 199-I 0 .i-1------/----.L..-f.-....r------1'------j

A.robustus

A.boisei 0 OH 5

0 3 Principal Component I 46

Table 10

Principal Component Scores

Mandibular Dentition

Principal Component Specimen PC 1 PC 2 PC 3 PC 4 PC 5 PC 6

ER 729 1.40 1.13 1.00 0.60 -1.00 -0.60

ER 992 -1.15 0.72 0.20 -1.40 0.57 -0.97

LH 3 -0.46 2.37 -0.77 0.43 2.00 0.32

MLD 18 -0.66 0.90 0.82 0.70 -0.40 1.17

MLD 40 -0.48 -0.33 -0.77 0.10 -1.82 -0.10

Peninj 1.81 -0.77 1.60 -1.13 0.25 -0.70

OH 7 -0.23 -0.24 -1.82 -0.11 -0.35 -1.10

SK 23 0.89 0.67 -0.50 -1.36 -0.17 2.11

STS 7 -0.80 -0.47 0.30 1.60 0.41 0.14

STS 52 -0.32 -0.38 -0.04 0.60 0.54 -0.34 47

Figure 9 Bivariate Plot of Principal Component Scores Mandibular Dentition 3

A.afarensis 0 2 LH 3

H H MLD 18 fi\ER 729 b 1 Q) ~ 0 II 1 A.robust us 0.. E A.africanus I I 0 0 I 0 rl ctl 0.. •rl STS t) ~ I •rl I ~ H.habilis p.., 1 -~~ Peninj A.boisei

2

3~-----,,,------,,------L------,,------rl------~ 2 1 0 1 2 3 Principal Component I 48

patterns of relationships produced by principal component analysis.

From these analyses the following interpretations are suggested:

1) in either Figure 8 or 9 the Hadar-Laetoli specimens appear to be closer to the gracile hominids (A.africanus and Homo habilis) rather than to the robust hominids (A.robustus and A.boisei) and 2) the maxillary dentition (see Figure 8) appears to display a larger range of variability (based on the spread of specimens on each component) than does the mandibular dentition (see Figure 9).

C. Canonical Variate Analysis

To test the null hypothesis that the Hadar-Laetoli hominid fossils (A.afarensis) to not differ significantly from other forms of australopithecines, canonical variate analysis was performed. This analysis included the following groups (see Table 11): A.afarensis,

!·africanus, and A.robustus. To maximize sample size, H.habilis and

A.africanus specimens were combined to form a gracile early hominid group and A.boisei and !·robustus specimens were combined to form a robust early hominid group.

From the results of the F-tests of the Mahalanobis n2, it would appear that: 1) Australopithecus afarensis is significantly different from A.africanus and A.robustus, when their maxillary teeth are com­ pared, but that 2) A.afarensis is not significantly different from

A.africanus and A.robustus when their mandibular teeth are contrasted.

This may be due to the fact that the analysis performed on the man­ dibular dentition lacks a uniform sample size for the three groups of hoininids. 49

Table 11

F* Test of Mahalanobis D2

Maxillary Dentition

A.robustus A.africanus A.afarensis

A.robustus (n=5)

A.africanus (n=4) 2.24

A.afarensis (n=3) 17.86 8.29

*Critical value of F for 5 and 5 degrees of freedom equals 5.05 (Probability = 0.05)

Mandibular Dentition

A.robustus A.africanus A.afarensis

A.robustus (n=3)

A.africanus (n=6) 7.38

A.afarensis (n=1) 3.21 4.77

*Critical value of F for 6 and 2 degrees of freedom equals 19.33 (Probability = 0.05) 50

Figures 10 and 11 are bivariate plots which were produced by the canonical variate analysis. These plots suggest the following: 1) that Australopithecus afarensis is a distinct and separate species closer to gracile than to robust early hominids and 2) there appears to be a greater range of variability, based on the spread of specimens on each component, exhibited by the mandibular dentition (see Figure

11) compared to that for the maxillary dentition (see Figure 10).

The final statistical results produced by the canonical variate analysis was the jackknifed classification table. Table 12 presents the number of cases correctly classified into the groups A.afarensis,

A.africanus, and A.robustus. Furthermore, the significance of Table

12 is that only a single A.africanus was classified as being a member of the proposed species A.afarensis. This specimen represents approx­ imately 16.67% of the sample from Table 11 mandibular dentition.

Summary of Results

The results for the univariate and multivariate statistical analyses are as follows: histograms and principal component analyses suggest that maxillary and mandibular post-canine teeth exhibit con­ siderable variability in mesio-distal and buccal-lingual measurements.

The principal component analysis shows a larger range of variability for the maxillary dentition than for the mandibular dentition. The reverse is true for the canonical variate analysis. From the results shown in the bivariate plots, it would appear that the Hadar-Laetoli specimens are allied closer to (yet separate and distinct from) A. africanus and Homo habilis specimens (see Figures 8 and 9) than other members of the Fossil Hominid sample. The canonical variate analysis 6 ·~ I

5 ~ I

4 -j !_.afarensis I tJj 3 OH 5 1-'• H ~ H '1 * !_.robustus 1-'• Q) 2 rl ~ .g SK 48 (1) •rl 1 AL 199-I SK 55 '"d 1'-1 AL 200-Ia 1-' * 3:01-z;! ~ 3 * ~ c+ 1-'• 0 ,,_ --·-~-· rl -----* ____ .. 1-'·0~ ttl STS 52. 1-' H) '1 0 -1 1-' (1) •rl I» 0 !:: 0 * '1~1--' -2 <:..::: 0 ~ SK 27 t.:> '* &81-'• ER 1590 ::s 0 c+!» -3 \·, 1-'• 1-' * c+ I-'•

Ln f--0 ------I 6

-~· -- 5 J I - -~- P;_.robustus Nat• ron A.b. 4 I I ( -- 'I tJj 3 1-'• A.africanus MLD ~.0 H - ~ H * * SK 23 ) 'i 2 1-'• Q) ...---1 ' ~ .g ' * ERl729 (!) 1 ( \STS 5 2 •r-1 * \ "tt H STS 7 I--' ro *M LD 18 :S::Oiozj :> 0 * ~ c+ 1-'· ...---1 0..0~ ro -1 * OH 7 1-'• H) 'i t.) ER 992 " H.h. g' 0 (!) ·r-1 H.h. / s:: *"'------·---· 1---'llll-' 0 ------lll::SI-' § -2 'i § 0 t::ll-'• (!) (") -3 8-~ 1-'• c+<: I-'• Ill -4 ~ I I 0 'i ::s 1-'• ~ -5 -l I I (!) ~ Ill -6 j A_.afarensis I I J< (I) 1-'• (I) I -4 -3 -2 -1 0 1 2 3 4 5 6 Canonical Variable I

IJ1 N 53

Table 12

Jackknifed Classification

Maxillary Dentition

Percent Number of Cases Classified into Group Group Correct A.robustus A.africanus A.afarensis

A.robustus 80.00 4 1 0

A.africanus 75.00 2 3 0

A.afarensis 100.00 0 0 3

Total 85.00 5 4 3

Mandibular Dentition

A.robustus 66.66 2 1 0

A.africanus 83.32 0 5 1

A. af arens is 100.00 0 0 1

Total 83.32 2 6 2 54

suggests that A.afarensis does indeed differ significantly from A. africanus and A.robustus, for the maxillary but not the mandibular dentition. Finally, from data obtained from the jackknifed classi­ fication table produced by canonical variate analysis, it would appear that the Hadar-Laetoli fossil specimens would be best classified as being members of the proposed species, Australopithecus afarensis. CHAPTER V

DISCUSSION

Results of the 1) review of the pertinent literature, 2) statistical analyses, and 3) implications presented by these results will be discussed in this chapter.

The purpose of this thesis was to test the null hypothesis that

Australopithecus afarensis is not significantly different from any other Plio-Pleistocene hominids. As stated in Chapter 2 (Literature

Review) strong arguments have been presented by Johanson (1980),

Johanson and White (1979), and Johanson et al. (1978) that disagree with this null hypothesis. Included within these arguments are the following: 1) the fact that the Laetoli and Hadar specimens exhibit primitive characteristics in dental, cranial and postcranial mate­ rial, 2) Articles 13s(i) and 72, and Recommendations 72A, 73B and

73C of the International Code of Zoological Nomenclature support

Johanson and White's taxonomic classification of this material, and

3) geographical isolation of the proposed species Australopithecus afarensis.

Morphological Characteristics

Morphological characteristics associated with the Laetoli and

Hadar specimens described in detail in Chapter 2 (Literature Review) do exhibit certain primitive features which are diagnostic of the species Australopithecus afarensis, such as: 1) a C/P3 dental

55 56

cutting mechanism, 2) sectorial P3, 3) presence of a diastema between

the canines and lateral incisors, 4) strong alveolar prognathism, and

5) a high degree of skeletal robusticity in "regards to muscle and

tendon insertions" (Johanson and White, 1979:324). Certain primitive

features which are diagnostic of the proposed species A.afarensis can

also be associated with fossil remains for the hominid A.africanus

from the South African site of Sterkfontein, as suggested by Kennedy

(1979). It should be noted, however, that no Pliocene or Pleistocene

fossil hominid remains (according to the information available to

this author) exhibit the total spectrum of primitive morphological

characteristics that are associated with the proposed species

Australopithecus afarensis.

International Code of Zoological Nomenclature

The aforementioned Articles and Recommendations of the Inter­ national Code of Zoological Nomenclature provide further evidence for the rejection of the null hypothesis. Foremost, the taxonomic validity of the proposed species Australopithecus afarensis can be substantiated by the following Articles and Recommendations of the

International Code of Zoological Nomenlature: 1) Articles 13a(i) and 72 and 2) Recommendations 73B and 73C. By satisfying these

Articles and Recommendations, Johanson (1980) has solidified his claim to a valid taxonomic name within the constructs of systematic zoology (Mayr, 1969). Furthermore, Recommendation 72A of the Inter­ national Code of Zoological Nomenclature assures future researchers of accessibility to the holotype (LH 4) of the species Australopi­ thecus afarensis. This is paramount, for the holotype or "type" 57

specimen is the standard of reference for determining the applica­

bility of any taxonomic name. The holotype is the focal point of a

taxon, and does not change. Finally, once the holotype of any taxon

conforms with the Articles and Recomendations of the International

Code of Zoological Nomenclature, it is not subject to change except

under the specific plenary powers of Article 79 (Mayr, 1969).

Geographic Isolation

The final argument that I shall discuss from Chapter 2 is the

topic of geographic isolation. Buettner-Janusch (1973) has stated

that both reproductive and geographic isolation are fundamental

requirements for the allopatric speciation process to occur. The

process of hominid speciation could have occurred either by 1) ana­ genesis or phyletic evolution (evolution of one species from another

of the same lineage) or 2) cladogenesis (the splitting of one lineage

into two lineages) (Wolpoff, 1980). Brace (1972) and Wolpoff (1971,

1973) support the phyletic evolution process. They suggest that the differences between the gracile and robust forms of australopithecines

is simply the result of sexual dimorphism. However, Wolpoff (1980) has modified his interpretation of hominid taxonomy and now maintains

that two species of the genus Australopithecus, A.africanus and A. robustus are represented in the fossil record. Other researchers such as Louis Leakey (1966), Richard Leakey (1972) and Robinson (1963) support the cladogensis (two lineages) process of hominid speciation and consider this variability to represent a phyletic scheme involving two or more contemporary genera. 58

Robinson's dietary hypothesis, first proposed in 1953, has con­

tributed much to multilinear concepts of hominid evolution. Robinson

argues that morphological differences within the australopithecine

groups necessitates recognizing two genera, Australopithecus (gracile hominids and Paranthropus (robust hominids). Furthermore, Robinson maintains that these dietary differences exhibited by Australopithecus

(a carnivore) and Paranthropus (a vegetarian) are a reflection of

adaptation to different habitats.

Researchers, such as Louis Leakey (1966) and his son Richard

(1972), who support the multiple lineage theory, have taken an ex­

treme view by claiming that three contemporary hominid lineages

(A.africanus, A.boisei and H.habilis) may be represented in the

Pleistocene deposits of East Africa.

The method of speciation is a crucial issue in hominid evolution and it would directly affect the nature of the basal hominid adaptive pattern. Speciation could either have been: 1) multilinear, which would allow radiation and subsequent divergence or, 2) unilinear evolution of a taxon (Wolpoff, 1980).

Statistical Results

From the statistical results discussed in Chapter 4 (Results), the findings from the principal component and canonical variate analyses support the rejection of the null hypothesis.

Bivariate plots of principal component scores (Chapter 4,

Results, Figures 8 and 9) illustrate the patterns of relationships exhibited by the Fossil Hominid sample specimens. Analysis of the maxillary dentition (Figure 8) suggests that A.afarensis is distinct 59

from A.africanus and A.robustus and A.boisei. Furthermore, it would

appear from Figure 8 that A.afarensis displays maxillary dental char­

acteristics which are similar and phyletically closer to those of the

gracile forms, ~.africanus and H.habilis, than to the robust forms,

A.robustus and A.boisei. From the analysis performed on the mandib­

ular dentition (Figure 9) it would appear that the single A.afarensis

specimen displays no close dental affinities with other members of

the Fossil Hominid sample. Finally, the maxillary dentition (see

Figure 8) appears to display a larger range of variability (based on

the spread of specimens on each component) than does the mandibular

dentition (see Figure 9).

The F-test results produced by canonical variate analysis offer

the following interpretations. First, A.afarensis is significantly

different from either A.africanus or A.robustus for the maxillary

dentition. Second, there are no significant differences among A.

afarensis, A.africanus, and A.robustus for the mandibular dentition.

Third, bivariate plots obtained from the canonical variate analysis of maxillary and mandibular dentition (Figures 10 and 11) suggest

that 1) Australopithecus afarensis is a distinct and separate species

and 2) there appears to be a greater range of variability, based on

the spread of specimens on each component, exhibited by the mandibu­

lar dentition (see Figure 11) compared to that for the maxillary dentition (see Figure 10). Finally, the jackknifed classification

table (Table 12) produced by the canonical variate analysis presents the number of cases correctly classified into the groups A.afarensis,

A.africanus, and A.robustus. The significance of Table 12 is that only a single A.africanus was classified as being a member of the 60

proposed species A.afarensis. This specimen represents approximately

16.67% of the sample from Table 12 mandibular dentition.

From these statistical results, it would appear that: 1) prin­

cipal component analysis shows a larger range of variability for the maxillary dentition than for the mandibular dentition, but 2) the

reverse is true for the canonical variate analysis, and 3) it would

appear from the bivariate plots that the Hadar-Laetoli specimens are

phenetically closer to (yet separate and distinct from) A.africanus

and Homo habilis specimens (see Figures 8 and 9) than other members

of the Fossil Hominid sample. Furthermore, analyses performed on

mandibular dentitions suggest the following as possible explanation

for the apparent lack of significant differences seen between cer­

tain pairs of samples of the Fossil Hominid sample. CHAPTER VI

CONCLUSION

This thesis has been an attempt to test the hypothesis that

Australopithecus afarensis is not significantly different from any other Plio-Pleistocene hominid. Fossil remains for this hominid date to the Pliocene in Eastern Africa. The similarities between fossil remains at Hadar and Laetoli suggest that these remains represent a single taxon (Johanson, 1980).

The proposed fossil hominid, A.afarensis, has an array of primitive features. These include the following: 1) presence of a diastema between the lateral incisors and canines, 2) large projec­ ting canines, 3) two or three distinct roots in the p3•s, and 4) a parallel dental arcade (LH 4 exhibits posterior divergence) (Johanson and White, 1979). Postcranial skeletal remains for A.afarensis strongly suggest that this hominid was capable of habitual bipedal­ ism and analysis of pelvic and knee bones supports this argument

(Johanson et at., 1976; Lovejoy et al., 1973). Further evidence for bipedal locomotion can be found in the analyses foot bones and foot­ prints. Mary Leakey and co-workers have proved conclusively that not only did A.afarensis walk erect, but also had a well developed foot which is similar in construction to that of Homo sapiens (Leakey,

1979; Leakey and Hay, 1979).

Opinions vary on how to classify the fossil material found at

Hadar and Laetoli. Johanson and White (1979) consider the material

61 62

to represent a new form of australopithecine. Leakey and Hay (1976) suggest that material from Laetoli and the Garusi fragment are similar to specimens assigned to the genus Homo in East Africa. Wolpoff

(1980) argues that A.afarensis resembles A.africanus too closely to be considered a separate species. Results from canonical variate analysis suggest that !·afarensis does differ significantly from other forms of Plio-Pleistocene hominids when maxillary dentitions were analyzed.

Several morphological features that Johanson and White (1979) thought were characteristics of A.afarensis can be seen in post­ cranial remains from South Africa. The capitate of A.afarensis, which has been described as "waisted," and lack of a styloid process on the third metacarpal is similar to some fossil remains from Sterk­ fontein. Also, the innominate bone AL 288-I is very similar in size and morphology to fossil remains from Sterkfontein (Sts 14) (Kennedy,

1979).

The fossil remains of A.afarensis do show characteristics that are not represented in A.africanus such as: 1) upper central incisors that are very broad, 2) lateral incisors that are relatively small in

A.afarensis, 3) diastema between the lateral incisors and the canines, and 4) a canine/premolar dental cutting complex. The morphological similarities between the Hadar and Laetoli fossils suggest that for one million years A.afarensis did not undergo any major evolutionary changes. A further characteristic of the proposed species !·afarensis is the fact that these remains come from a geographic area which has not produced fossil materials for other known Plio-Pleistocene hom­ inids. Therefore, based on: 1) the results of the statistical 63

analyses of dental measurements, 2) geographic isolation, 3) morphological characteristics, and 4) review of the pertinent literature, it is suggested that Australopithecus afarensis be

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