New Australopithecus femora from East Rudolf, Kenya

New Australopithecus Femora from East Rudolf, Kenya

Alan Walker Department of Human Anatomy. University of Nairobi, Kenya

New fossil femora attributed to Arcstra1ofdhc.u-s from East Rudolf, Kenya, form the basis for a three-dimensional reconstruction of a compIete femur. The reconstruction and the known fossils are compared with the femora of Homo sapins. Although many of the features of the fossil bones fall within the overall ranges to be found in modern man, there seems, nevertheless, to be a distinctive total pattern in the femoral anatomy of Australopithcus. Biomechanical explanations for this pattern may be possible when other postcranial bones can be reconstructed with the same degree of certainty as the femur.

Received 26 October 1972

1. Introduction Until recently proximal remains.

our knowledge

of the femur of AustraZo@zecus has been limited

to either

or distal fragments from deposits yielding Australopithecus dental or cranial As yet no definite association of femoral and dental material has been shown, but

other associated parts from East Rudolf strongly suggest that the past and present assigning of nearly all the femoral fragments discussed here to Australopithecus species is probably correct. femoral

New material fragments,

from

East

Rudolf,

one of which comprises

Kenya

(Leakey,

197 1, 1972)

the distal end together

includes

four

with most of the shaft.

These new fossils give a much more complete idea of the size and morphological variability of this bone and also provide a sound basis for a complete reconstruction of one size of femur. In this account state

that

Australopithecus

specimens,

I am not involved motor

I shall be referring

to previous

I can find no real differences,

apart

descriptions

here with the question

as to whether

that all the Australopithecus

from one variable

and/or dimorphic

species through

similar

to attempt

proximal

time.

a composite

2. Femora from South than East Rudolf Three

of

this reflects merely similar loco-

or the possibility

is sufficiently

anatomy

whether referred to as A. africanus, A. robustus or any other species.

capabilities,

morphology

and must at the outset

from size, in the femoral

specimens

In any event,

description and East

pieces and two distal pieces have been recorded

proximal fragment is known from Olduvai Gorge in Tanzania. Sts 14. The proximal fragment from Sterkfontein is associated

are sampled the femoral

for Australopithecus. Africa

Elsewhere

from South Africa.

One

with a pelvis and partial

vertebral column. Broom & Robinson (1950) reported this bone as “rather badly crushed” and that “for the most part the surface of the bone is not well enough preserved to show satisfactorily the muscular ridges.” Dr C. K. Brain (in Day, 1969) is quoted as saying that the bone is badly crushed, the head extensively reconstructed and the surface of the bone damaged. My own observations confirm the essentially fragmentary nature of the specimen. The whole surface has the appearance of very many splinters of bone recemented by matrix. The “head” is almost totally comprised of plaster of Paris and fairly crudely Journal of Human Evolution (1973) 2, 545-555

546

A.

WALKER

reconstructed and it is not clear whether the neck length has been correctly gauged, although the acetabulum from the same side of the same individual gives a fair indication of head size. I could see no way of reasonably

estimating any measurements

or angles and,

short of gaining the impression that this is the smallest known femur of Australopithecus, very few useful points of comparison can be made. This is not to say that the sketch reconstruction

given by Broom

what it is, namely an attempt man.

& Robinson at comparing

is fanciful,

but that it should be taken for

the fossil fragment

with a femur of modern

SK 82. This is the proximal part of a right femur from Swartkrans and includes the head, neck, lesser trochanter and part of the shaft. It is much bigger than Sts 14 but again is reconstructed in part. Most of the greater trochanter is reconstructed and large cracks on the posterior

aspect of the shaft and lesser trochanter

have been filled with plaster.

The head is small and is just a little more than a hemisphere. flattened

anteroposteriorly

with a well-marked

robust and slightly platymeric divided into a smaller proximal SK 97. most

Much

The neck is long and

groove.

below the lesser trochanter. and larger distal fossa.

and

the shaft is cracked

details such as the double

and crushed

trochanteric

below

shaft is quite

trochanteric

fossa is

It is a little larger in the lesser trochanter.

fossa and the presence of an obtu-

rator groove are similar in the two specimens. Olduuai Hominid 20 (O.H. 20). Th is is part of the proximal lacking the head, part of the greater trochanter

The

The

the same parts are preserved in this as in SK 82.

dimensions

Morphological

obturator

portion

and lesser trochanter.

of the left femur, It is quite similar

in size and morphology to the two Swartkrans fragments (Day, 1969). 3s 34. This is the distal extremity of a right femur from Sterkfontein with the posterior part of the medial condyle

missing.

The maximum

bicondylar

width is 64.0 mm.

bone is relatively small compared the shaft relative measure

The

to the same part in modern man but the robusticity angle is difficult to the width is quite great. The condylofemoral

but estimates have ranged from “at least 7””

(Clark,

1947) to 15’ (Heiple

of to &

Lovejoy, 1971). The patellar groove is quite deep and the lateral lip is more strongly developed than the medial. The condylar contours show a flattening on their most distal parts.

The intercondylar

fossa has been considered

deep but falls in the range of modern

man. TM 1513. This is approximately the same part as preserved in Sts 34, but from the Some outer bone is missing from the left femur of another individual from Sterkfontein. suprapatellar

area and a large flake of bone is missing from the lateral epicondylar area. MLD 17. Half a femoral head from Makapansgat, noted and figured by Bone (1955), is roughly the right size to be from an Australopithecus femur, but it has a peculiar widened fovea and an oddly formed epiphyseal line. Identification of this fragment is uncertain, to say the least, and I consider it unwise to include this in the Australopithecus sample. 3. Femora

from

East

Rudolf,

Kenya

The following specimens have been recorded and described from the East Rudolf deposits (Leakey, 1971,1972; Leakey, Mungai &Walker, 1971, 1972; Leakey & Walker, 1973). KNM. ER. 738. This is the head, neck, lesser trochanter and part of the shaft of a left femur of small size. The head is small and nearly hemispherical, and the neck is long and The shaft is intact for some distance below the lesser anteroposteriorly compressed.

NEW

FEMORA

AUSTRALOPITHECUS

FROM

547

KENYA

trochanter but more distally it is split roughly sagittally and only the medial half preserved. On this distal part of the shaft there is clear evidence,

amplified

by skiagrams,

of a

the cortex fracture callus. The osteone arrangement on the surface is disorganized, strikingly thickened and the skiagram shows the typically “woven” appearance of the healed fracture. Because of this fracture and the possibility of compensatory remodelling of the neck region, it is perhaps unwise to take the morphology exactly typical. KNM. ER. 815.

This is the proximal

of this specimen

as being

part of a left femur with the neck, most of the The neck is long as judged by the distance

lesser trochanter and part of the shaft preserved.

to the epiphyseal line and strongly compressed anteroposteriorly. This compression is so strong that an inferior crest is developed where the anterior and posterior surfaces of the neck meet at an acute angle. The distal part of the lesser trochanter is preserved. This is directed at an angle of about 40’ to the axis of the neck when seen in superior view. The gluteal

tuberosity

posteromedial

is a low, roughened area and an hypotrochanteric fossa is present to it. The shaft is very platymeric as far as it is preserved and the medullary

cavity at the level of the distal fracture is surprisingly narrow. KNM. ER. 736. This is part of the shaft of a massive left femur. lesser trochanter

to about

the divergence

of the supracondylar

It extends from the

lines.

The shaft has a

gently convex anterior surface and is buttressed behind by a massive, trenchant femoral crest. The cortex in the region of the base of the neck is very thick as seen on the proximal fracture and in skiagrams. This specimen is the distal three-quarters of a right femur with the Some areas are affected by abrasion fracture just below the lesser trochanter. corrosion. These are the suprapatellar area, the distal part of the medial surface,

KNM. ER. 993. proximal and/or

the popliteal

surface and the condyles,

particularly

the lateral.

The shaft is moderately

robust and platymeric in its proximal part but pilaster development gives the bone a more nearly circular cross section in the midshaft region. The anterior surface is evenly convex but this changes to give relatively flat medial and lateral surfaces on either side of the pilaster. The shaft is bowed anteriorly to a moderately strong degree and the pilaster development

does not make the linea aspera straight in lateral profile as in KNM.

The area of the popliteal

ment of a ridge that divides it into medial and lateral portions. not much raised above

ER. 736.

surface is relatively small and gently convex due to the developthe level of the suprapatellar

The patellar groove is

area in the midline.

The lateral

margin is much more developed

than the medial and is essentially continuous with the ridge that forms the lateral surface of the suprapatellar area. The intercondylar fossa is deep and wide and impressions for the cruciate ligaments are as in modern man. The total epiphysis is wider mediolaterally than it is anteroposteriorly femorocondylar angle to the diaphysis.

4. Evidence

from

and is set at a marked

the Skiagrams

Only a preliminary study has yet been made of the skiagrams of the East Rudolf fossils. Two points are worth mentioning at this stage. One is that the cortical thicknesses of the shaft are very great and the other is that the cortex of the inferior part of the neck is thickened for a considerable distance medially. The radiation of trabeculae that fans out into the femoral

head and which is seen in the anteroposterior

view, begins where the

548

A. WALKER

neck cortex thins out about mid-way and neck as in modern

along the neck and not at the junction

of the shaft

man.

5. The Size Range in Australopithecus

Femora

There have been suggestions in the past that the post cranial bones of robust and gracile australopithecines show distinguishing features other than size. As the femoral evidence from South Africa stands, the gracile form is represented by one crushed and fragmentary specimen

and two distal pieces.

based on Broom’s on the specimen. no meaningful

The

differences

put forward

sketch of Sts 14 and on Broom Zihlman

(1971),

by Napier

& Robinson’s

tentative

(1964)

were

observations

noting the crushed nature of the specimen,

could find

differences between the Sterkfontein and Swartkrans femora.

Heiple & Lovejoy in a series of papers have convinced Broom’s reconstruction, that the differences are minimal. from deposits that have yielded

More recently themselves, while accepting The East Rudolf fossils come

many cranial and dental remains of Australopithecus

and

the situation there seems to have been made much simpler, in that only one sexually dimorphic

species seems to have been sampled

range in cranial

and dental

(Leakey,

1972).

Just as there is a wide size

parts, there is also a wide size range in the post cranial

material, including femora. After an examination of the South African post cranial fossils, I am myself convinced that there is as yet no clear evidence of any major differences in morphology

between

specimens

that could be called robust or gracile sampled from the

various sites. As far as size alone goes, the new East Rudolf the known femoral material in some, more or less accurate,

material

smallest to largest, the femoral fragments are : Sts 14; KNM. TM

1513;

particular

Sts 34 and SK 82; SK 97, O.H. 20 and KNM. interest is the close agreement

one from Sterkfontein

allows us to place

order of size. In order, from ER. 815;

ER. 993;

KNM.

KNM.

ER. 738;

ER. 736. Of

in overall femur size between Sts 34 and SK 82,

and the other from Swartkrans.

the shaft of proximal fragments. The maximum width of the distal epiphysis

Table

is as follows:

1 gives size indications TM

of

1513, 57.0 mm (est) ;

Sts 34,64-O mm and KNM. ER. 993,69-O mm (est). I realize, of course, that at least two femora of different size and on which upper and lower measurements can be taken are needed to place accurately any isolated proximal or distal part in its size order, but KNM.

ER. 993 does allow a strong impression to be gained, for the first time, of upper and

lower sizes, and the size order given here is unlikely to be substantially

Table

Diameters

1

of shaft

Anteroposterior diameter (AP) Specimen Sts 14 KNM. ER. KNM. ER. SK 82 SK 97 O.H. 20 KNM. ER. KNM. ER.

(mm) 815 738

993 736

just

below

Mediolateral diameter (ML) (mm)

Not measurable but very small 18.3 26.2 22.5 26.5 25.0 30.0 24.2 33.3 26-O 33.0 25-5 32.4 30.0 40.0

the lesser

AP+ML 2 (mm) 22.25 24.50 27.50 28-75 29.50 28-95 35.00

incorrect.

In any

trocbanter

Platymeric Index AP x 100 ML

69.84 84.90 83.33 72.67 78.78 78-70 75.00

NEW

549

PEMORA FROM KENYA

AUSTRALOPITHECUS

event, the evidence indicates that femora of the same size are likely to be found at Sterkfontein and Swartkrans. 6. A Reconstructed

Femur of Australopithecus

An attempt

has been made to model a complete femur based mainly on East African KNM. ER. 993 provides the specimens. Figure 1 gives four views of this reconstruction. basis for the reconstruction, with other East Rudolf specimens and O.H. 20 giving the of the abraded condylar guide lines for the trochanters, head and neck. Remodelling surfaces was attempted ligament

using the remaining

morphological

pit) and skiagrams as well as following

points (e.g. fibular collateral

the contours of the remaining

patches of

outer bone. I must admit, however, that memories of the two Sterkfontein distal fragments must inevitably have led my hand during this part of the reconstruction. The total length of the reconstruction (Martin & Sailer, No. 2) is 360-O mm. In anterior view the shaft is stout and straight and the proximal platymeria and the supracondylar The neck is long and set at a low angle expansion distally give it a waisted appearance. to the shaft.

The head is small and not much more than hemispherical,

rather than the

Figure 1. (a), Anterior, (b), posterior, (c), medial and (d), lateral views of reconstructed femur of Austrdofiopithecus. The total length (head to medial condyle) is 360 mm.

550

A.

usual human

condition

does not project modern man. are placed tubercle

WALKER

where it is about

far proximally,

The femorocondylar

on a horizontal.

merging

two-thirds

of a sphere.

The greater

nor is it flared from the lateral

The

into the lateral

trochanter

side of the shaft as in

angle gives a strong valgus position when the condyles patellar ridge

groove

is wide with a well-developed

that borders

the depressed

The groove is not much raised above the suprapatellar aspera is short and the hypotrochanteric

area.

lateral

suprapatellar

In posterior

area.

view the linea

fossa is placed quite distally with a low tuberosity.

The lesser trochanter is placed rather medially on the shaft, even allowing for minor neck anteversion, and a distinct ridge, probably associated with the iliacus portion of m. iZz$soas runs laterally The intercondylar In lateral strong

to join

the medial proximal

expansion

fossa is wide and the popliteal

and medial

pilaster.

The

surface

views the shaft is anteriorly

lateral

condyle

of the linea aspera below it.

convex.

bowed and buttressed

has a flatter

curvature

than

behind

the medial,

by a

but the

posterior part of the lateral condyle has a smaller radius of curvature than that of the medial. The fovea is situated posterior to the coronal equator of the head. In superior view the neck is strongly compressed at an angle of about into a proximal condylar lateral

anteroposteriorly

smaller

pit and a distal much

deeper

fossa is deep and wide and the patellar tubercle

and the lesser trochanter

40” to the long axis of the neck.

more strongly

fossa is divided

one.

view the inter-

it must be remembered

specimens,

Martin

value

& Saller

of about

(1957)

12.0.

the robusticity

The

and Previous

is of a femur

mean

index (of Martin

is 15.36,

that would be

human

femora,

within

and Saller)

(but shows

where the index usually

for H. safiiens neanderthalensis is given

as 13.5 with Spy 14.1 and La Chapelle

Australopithecus reconstruction

Statements

fossils, and is based on one of the larger

the bone to be much more robust than modern has a mean

with the

Anatomy

that this reconstruction

called robust in terms of the South African East Rudolf

in profile,

developed.

on Femoral

not the largest)

In inferior

groove is V-shaped

7. The New Reconstruction

Although

is directed

The trochanteric

the range

14.0.

by

The index of the

of Pan troglodytes and Pongo

pygmaeus among the anthropoids. This robusticity could be due to several factors but among them are: d’ff I erences in bodily proportions between Australopithecus and H. sapiens (specifically a greater proportion resistance to greater bending moments neck,

greater

muscular

bodily proportions

development

of the mass in the head, neck, arms and trunk), in the femoral shaft due to the relatively longer in the thigh

of Australopithecus is practically

and lower limb bones are limited

to the humerus

To assume that they had bodily proportions to circularity of argument Lovejoy & Heiple (1970) since it is associated with think, given the state of the which the reconstruction Broom’s

of Australopithecus.

lacking since definitely

similar

and foot fragments

Evidence associated

for the upper

from Kromdraai.

to those of H. sapiens is likely to lead

when dealing in functional terms. attempted a reconstruction based mainly on the Sts 14 femur a pelvis that provides the interacetabular diameter. I do not Sts 14 femur, that the reconstruction is valid, but the method by was made is sound in principle. Measurements taken from

sketch and from published photographs do not, however, lend themselves to The East Rudolf material now makes it clear that the distal fragments from accuracy. Sterkfontein are from substantially larger femora than Sts 14 and this too affects the

NEW

Lovejoy

smaller

FROM

551

KENYA

The Sts 34 and SK 82 pieces that these authors

& Heiple reconstruction.

are now seen to come from femora much

FEMORA

AUSTRALOPITHECLJS

of approximately

than the reconstruction

used

the same size and which were not

based on KMN.

ER. 993.

I would estimate

the

length of such a femur as about 330-340 mm. This is greater than Lovejoy & Heiple’s estimate and probably reflects a greater interacetabular distance than that of the Sts 14 pelvis. The Sts 14 femur must have had a much smaller distal part than Sts 34 and this in turn means that the total reconstructed length must be somewhat smaller than Lovejoy & Heiple’s estimate of 276 mm. This is the smallest femur known and the total length may have been no more than 250 mm. The size of the head in the new reconstruction is small relative to other parts of the end of the bone. The diameter of the reconstructed head is 34-O mm. Values fen-

proximal

populations 1957).

of modern

When

man have means

ranging

the head size is normalized

from 36.0

to 47.8

for total femur length

(Martin

& Sailer,

(head diameter

x lOCl/

total femur length), the value for the reconstruction is 9.44, compared with a total range of 8.76 to 10.63 and a mean of 9.81 for modern East African femora. Of the fossil specimens available femoral

for which head diameters

can be taken the values are given in Table

heads in Australopithecus do not seem, therefore,

to be small for the femur length, although small relative to the shaft dimensions. When

Gieseler

compared

(1926)

with the total

of necklength

The

since the femur is very robust the heads may be

The neck length in the reconstruction mm.

2.

as some writers have suggestedl,

(as defined by Martin femur

x loo/total

length,

femur

& Saller No. 14~) is 5000

the necklength

length

is 13.89.

index This

as used by

compared

with

modern East African femora shows an exceedingly long neck. This index in H. sapiem ranges from 8.55 to 1 I.01 with a mean of 9.74. Using Martin & Sailer’s necklength (No. 14) in which the head too is taken into account, shaft index (Martin

& Sailer necklength

man that range from 15.00 to 20.00. #ygm.aeus and Gorilla gorilla, it is higher high index in the reconstruction extremely

small for the femur

index)

the length

of 20.28,

Although

is 73.0 mm, giving a neck/

compared

with those of modern

smaller

than the usual values for Pongo This than the mean for Pan troglodytes of 18.80.

is made more striking

by the fact that the head is not

A head of the mean diameter of modern man would give an even larger value for this necklength index. Neck lengths for Australopithecats are given in Table The neck-shaft Table

3.

modern

3. angle in the reconstruction

A total variation man, but Pearson

demonstrates

length.

is 116” and values for the fossils are given in

of 23” has been

recorded

& Bell (19 19) record

sexual dimorphism

by Martin

in man, with females having

by sometimes as much as 3” between the means of the sexes. lations of H. sa$ens range from 121” to 133” with an overall Australopithecus angles are, then, significantly

Table

2

Femoral

head

Specimen

Anteroposterior (mm)

SK 82 SK 97 KNM. ER. 738

34.2 37.2 33.5

& Sailer

(1957)

for

angles from 111.5” to 150” ! This angle higher angles than males Means for different popumean of about

127”.

The

less than is usual in H. sapiens. The neck in

diameters

diameter

in

Austrnlopithecus Superoinferior diameter (mm) 33.0 35.0 33.2

-

552

A.

Table 3

WALKER

Neck

diameters,

angles and neck-shape

indices

in Awtralo-

pithecus femora

Specimen SK 82 SK 97 KNM. ER. 738 KNM. ER. 815 O.H. 20

the

reconstruction

indices (of Martin

Anteroposterior diameter

Superoinferior diameter

(AP) (mm) 18.2 19.0 16.5 15.9 19-5

(SI) (mm)

SI (Martin and Saller) p. 569

Neck-shaft angle (Martin and Saller) No. 29

26.5 26.0 26.5 25.0 (min) 33.0 (est)

50.0 52.0 40.0 41.0 (est) 50.0 (est)

68.67 73.08 62.26 63.60 59.09

120” 118” 115” 115” (est) 115’ (est)

is compressed & Sailer,

Index AP x 100 Neck length (Martin and Sailer) No. 14c (mm)

anteroposteriorIy.

The

diameters

1957) of the fossils are given in Table

3.

and

index of neck shape has a mean of about 80.0 and a range of 70.0 to 90.0. to attribute

this compression

to greater

abduction/adduction

trochanter

does not flare out from the lateral

shape

man,

the

It is tempting

forces than in modern

man,

1971) are thwarted

by the

but bending moment studies such as those of Preuschoft (1970, presence of trabecular bone such as is found in the neck. The greater

neck

In modern

border of the shaft, a feature

that several authorities have noted (Napier, 1964; Day, 1969 ; Lovejoy & Heiple, 1972). Broom & Robinson (1950) hinted that the trochanter in Sts 14 was flaring as in modern man. I could not judge the issue on that imperfect pected then it would be atypical of Australopithecus Lovejoy

& Heiple

(1972)

state that the absence

due to the more laterally condylar

placed

projected

and maintaining

of flaring in the Swartkrans

There

of the trochanteric

fossa in Australopithecus,

rather

the proximal

the angle between

the body as in man. insertion

but if it was as they susas we now know them.

shaft, but this could also be related

angle at the distal end of the bone causing

more laterally

specimen, specimens

placed

of the m. obturator extemus tendon inferiorly.

with

arrangement

the mm. obturator

of

of the details

internus and gemelli

and a much deeper and separate This impression

is

part of the shaft to be

the neck and the midline

seems to be a more or less constant

high and anteriorly

specimens

to the high femoro-

impression

is very deep indeed in SK 97.

The position of the lesser trochanter has been stated frequently as being more laterally placed than in modern man. Recently, Lovejoy & Heiple have questioned this and point out the problems associated with anteversion of the femoral neck and the static position of the trochanter.

An illustration

of the variability

in this feature in modern

even more dramatic than Lovejoy & Heiple’s figure is Martin & Saller’s it happens the femora from East Rudolf possibly have the lesser trochanters

man that is

figure 437. As more medially

placed than in modern man and it is quite clear that there is just as much variability

here

as in H. sapiens. The question of the development of the intertrochanteric line in Australopithecus has also been dealt with by Lovejoy & Heiple (1972). They point out that the line is variably developed in man and that Australopithecus does not fall outside the human range in this feature, as had been claimed previously. The line in the fossils seems to curve rather medially on its course towards the lesser trochanter and this is probably due to the long neck. Despite this, the fact remains that, of five specimens that have the region well enough preserved, there is not one that shows a strongly developed intertrochanteric line.

NEW

The

shaft is platymeric

diameters

to hyperplatymeric

in the midshaft

evidence

available

A low gluteal elongated

AUSTRALOPITHECUS

region,

at present,

hypotrochanteric

FROM

in its upper

especially

it appears

swelling is present

FEMORA

part,

in the larger

but has more

individuals,

that pilaster development

553

KENYA

where

equal on the

is proportional

to size.

on all the fossil bones with that part preserved

and an

fossa is again

present

on all bones

that show the area.

A

small crest proximal to the fossa may or may not be present. In the large specimen, KNM. ER. 736, the fossa is very low on the shaft, centred some 60.0 mm below the distal margin of the lesser trochanter. The suprapatellar surface in the reconstruction as Heiple anterior could

& Lovejoy position

(1971)

relative

not know,

angle

and the condyles are placed, distal pieces,

to the most distal part of the diaphysis.

however,

is that

the excavated

bowing of the shaft brings the more proximal to the condyles,

is concave

showed for the two Sterkfontein suprapatellar

What area

and

the position in modern man. Most previous estimates the vertical.

an

the anterior

parts of the shaft more anteriorly

thus approaching

is 105” or 15” from

in rather

these authars in relation

The femorocondylar of the angles in the

Sterkfontein pieces have been lower, probably, than the true values, mostly because the remaining distal portions of the shaft are too short to determine the shaft axis accurately. Clark (1947)

said that the obliquity

he arrived at his estimate. a range

of 4-17”

criticized critique

for normal

(if not scorned)

in TM

1513 was “at least 7”“, and he described

He also quoted Parsons male

English

by Pearson

femora.

& Bell

of possible (and to them actual)

(1914)

(1919)

problems

how

as giving an average of 10’ and

Parsons’ methods were severely and those authors give a lengthy

of mensuration

of this angle.

Measure-

ments for modern man are, however,

usually in the region of 9-l lo and Martin & Sailer give ranges of 4&l 7” for both sexes in man. Pearson & Bell’s mean values for males and females are: 8.7’ and 11.6’ for right and left male femora with S.D.‘S of 2.018 and 1.890, and 9.4” and 1 l-8” for right and left female femora with over 6 % of the 817 femora difficult to measure

that they measured

the angle in the Sterkfontein

of shaft was not enough to encourage to measure

confidence.

this angle on casts and furthermore KNM. ER. 993 vindicates

the event, specimen

S.D.‘S

of 2,135 and 1.890.

had angles over 14’.

A little

I myself found it

specimens, because the remaining length Heiple & Lovejoy however, attempted were brave enough to state it boldly. In their stand and their estimates of 15” and

14” for Sts 34 and TM 1513 conform with the angle in the new reconstruction. Kern & Straus (1949) took Clark’s figure and used it as an accurate one instead of an estimated minimum

value.

It is clear, then, that the genu ualgum of man was also similarly

Australopithecus. The building

seen also in Australopithecus. the lateral mass in his sketch of TM bone with no attempt had neither completely

present

in

up of the lateral border of the patellar groove as in man is KNM. ER. 993 shows that Clark probably underestimated

at reconstructing

15 13. Recently

Preuschoft

(197 1) has illustrated

the missing part and concludes

genu valgum nor genu varum, using this as evidence adapted for and quadrupedalism

incompletely

that bipedalism

abandoned.

this

that Australopithecus was in-

The angle between

the tangent drawn across the anterior patellar groove margins and the tangent across tlhe most posterior points of the condyles in distal view is of the order of 5’ in the human direction. Other anthropoid Primates have the angle in the opposite direction and this is presumably related to the genu varum position. The condylar index of Martin and Saller is 76.9 in the reconstruction. This is well within the range of the index for modern man, but somewhat higher than for H. sapiens

554

A.

WALKER

neanderthalem-is. Heiple & Lovejoy (1971) have discussed the shape and size of the intercondylar fossa and the contours of the condyles. Their conclusions are that most of the condylar features their findings. It is difficult

are very close to those of man and KNM.

to begin to understand

without

knowing

the morphology

material

from East Rudolf

the functional

and proportions

includes

ER.

993 serves to confirm

morphology

of one particular

bone

limb skeleton.

New

of the adjacent

part of a tibia as well as upper limb bones (Leakey

et al., 1972). It is highly likely that more postcranial bones of Austra~o~ithecus will be found in the East Rudolf area and the chances of finding associated bones are probably greater

there than in any other African

here is based on relatively remodelled

proximal

as much certainty

deposits now known.

material,

end is justified.

When

The reconstruction

but new finds will show whether

offered or not the

other limb bones can be reconstructed

as the femur and when the proportions

then biomechanical convincing

complete

analyses of the post cranial

of the limb skeleton

with

are known,

parts of Australopithecus will become

more

than they are at present.

8. Conclusions New fossil material

from East Rudolf

provides

the basis for a three-dimensional

recon-

struction of a moderately large-sized femur of Australopithecus. The foIlowing are the features by which the reconstructed femur, the fossils upon which it is based and other fossils described earlier, differ from H. sapiens femora: (I) The femur is more robust than is usual in H. sapiens. (2)

The femoral

relating

head diameter

lies in the low part of the range for H. sapiens. An index

head size to femur length is, however,

not much below the mean value for modern

man. (3) The

neck is very long and neck length

indices

fall well outside

the human

range.

Even when the head too is taken into account, an head + neck length index is higher than the highest in H. sapiens. This is despite the measuring of the neck length at a less oblique angle than in man (see 4). (4) The neck-shaft angle in Australopithecus is smaller

than is usual in H. sapiens, i.e. the

neck is set more nearly at right angles to the shaft axis. (5) The neck is more anteroposteriorly compressed in Australopithecus than in H. sapiens. (6)

The greater

trochanter

does not flare out from the lateral

profile

of the shaft as it

does in H. sapiens. (7)

The obliquity

of the femur in Australopithecus, as judged

is greater than is usual in H. sapiens. (8) There is a considerable size range in femora

by the femorocondylar

now attributed

angle,

to Australopithecus. The

smallest, from Sterkfontein, may have been only 250 mm long, while the largest, from East Rudolf, must have had a total length greater than the 360 mm reconstructed for the quite robust femur presented here. On the whole, Australopithecus femoral lengths are likely to be below and at the small end of the range of total lengths for human femora. (9) Although the human femur shows a high degree of variability and although many of the individual measurements and indices on Australopithecus fossils fall within the total ranges for those of H. sapiens, nevertheless a distinctive Australopithecus morphological pattern is gradually emerging as more specimens are found.

NEW

AUSTRALOPITHECUS

FEMORA

FROM

KENYA

555

I thank Mr R. E. F. Leakey and the Museum Trustees of Kenya, Professor P. V. Tobias and Dr C. K. Brain for permission to study material in their care. I would like to thank my many colleagues who have freely discussed their ideas on the hominid post cranial skeleton, particularly, Professor M. H. Day, Professor P. R. Davis, Mrs G. Kennedy, Mr R. E. F. Leakey, Dr H. Preuschoft, Dr B. A. Wood and Professor M. H. Wolpoff. My sincere thanks go to Richard Leakey who made it possible for me to visit South Africa. References Bone, E. L. (1955). Quatre fragments post-craniens du gisements a Australopitheques de Makapansgat. Anthropologic 59, 462-469. Broom. R. & Robinson. T. T. (1950). Further evidence of the structure of the Sterkfontein ape-man, Plesikhropus. Transva~~Museu~ M&wir no. 9 (1). Clark, W. E. Le Gros (1947). Observations on the anatomy of the fossil Australopithecinae. Journal oj Anatomy 81, 300-333. Day, M. H. (1969). Femoral fragment of a robust australopithecine from Olduvai Gorge, Tanzania. Nature

221,230-233. Gieseler, W. (1926). Messtechnik der langen Gliedmassenknochen der Anthropoiden. Abderhalden’s Hdbch biol. Arbeits~t~de~ 7, 635. Heiple, K. G. & Lovejoy, C. 0. (1971). The distal femoral anatomy of Australopithecus. American Journal of Physical Anthropology 35, 75-84. Kern, H. M. & Straus, W. L. (1949). The femur of Plesianthropus transvaalensis. American Journal of Physical Anthropology 7, 53-77. Leakey, R. E. F. (1971). Further evidence of Lower Pleistocene hominids from East Rudolf, North Kenya. Nature 231,241-245. Leakey, R. E. F. (1972). Further evidence of Lower Pleistocene hominids from East Rudolf, North Kenya, 1971. Nature 237,264-269. Leakey, R. E. F., Mungai, J. M. & Walker, A. C. (1971). New australopithecines from East Rudolf, Kenya, American Journal of Physical Anthropology 35, 175-186. Leakey, R. E. F., Mungai, J. M. & Walker, A. C. (1972). New australopithecines from East Rudolf, Kenya (II). American Journal of Physical Anthropology 36, 235-252. Leakey, R. E. F. & Walker, A. Cl. (1973). New australopithecines from East Rudolf, Kenya (III). American Journal of Physical Anthropology (in press). Lovejoy, C. 0. & Heiple, K. G. (1970). A reconstruction of the femur of Austrulopithecus africanus. American Journal of Physical Anthropology 32,33-40. Lovejoy, C. 0. & Heiple, K. G. (1972). Proximal femoral anatomy of Awtralopithecus. Nature 235, 175-l 76. Martin, R. & Sailer, K. (1957). Lehrbuch der Anthropologic 1. Stuttgart: Fischer. Napier, J_ R. (1964). The evolution of bipedal walking in the hominids. Archives de Siologie Liege 75 (Suppl). 673-708. Parsons, F. G. (1914). The characters of the English thigh bone. JournaZ of Anatomy 48,238-267. Pearson, K. & Bell, J. (1919). A study of the long bones of the English skeleton. Drapers’ Company Memoirs. Biometric Series 10,l-224. Preuschoft, H. (1970). Functional anatomy of the lower extremity. In (G. Bourne, Ed.), The Chimpanzee 3. Basel: Karger. Preuschoft, H. (1971). Body posture and mode of locomotion in early Pleistocene hominids. Foliaprimatologica 14,209-240. Zihlman, A. (1971). The question of locomotor differences in Australopithecus. Proceedings of the 3rd International Congressof Primatologv, Zurich, 1970, 1, 54-66.