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'.
".,DECIDUOUS DENTiTION
/;'
Th~ upper deCiduous dentition of Paranthropus crassidens is unknow~; except for two speCimens of the
second upper decidtious molar; but these arefbrtunately quite satisfactorily preserved.' The better of the
two teeth belongs to the child skull, and has already been figured in the view of tIie under side of the skulL
We refigure it twice natural size (Fig. 47B). It is a little worn down, bulall the structure is clearly shown.
The crown ofthis second milk molar is so closely similar in size to the first upper molar of modern man,
that it might readily be mistaken for a molar of true man. The antero-posterior length of the crown; ne~r
the middle of the tooth, is about 11·3 mm. It has been very slightly abraded in front by the first deciduous
molar and originally it 'may have measured 11 . 5' mm. The greatest width is 11 ·3 mm. The corresponding
measurem~ntsinthe other tooth 'we have, are n'I mm. and 12'1 mm.
'
, The tooth has four low cusps, of which the antero-internal has been the largest, and the antero-external
the second largest. The two main posterior cusps are much smaller. Ther:e is a rudiment of a fifth posterior
cusp. On the antero-internal corner of the tooth there is the indication of a small cusp, which would cor~
respond to the Carabelli cusp so often found in the adult teeth: Both this tooth, and the other one we have,
are a little too much worn to show if there had 'been any rudiment of a small antero-external cusp such as
we find in man.
FIG. 47.-The second upper left deciduous molars of tl;lree
Primates.
A. Possibly a species of Simopithecus (a baboon).
B. Paranthropus crassidens (male).
C. Bushman.
(All figures twice natural siZe.)
We have drawn for comparison the second upper deciduous molar of a fossil baboon and of a
Bushman (Fig. 47c). The baboon maxilla and premaxilla has only two teeth of the permanent set showing
and it is difficult to be sure of the species, but is certainly a baboon a little larger than the livingPapiopossibly a species of Simopithecus. The tooth is interesting as showing the four main cusps of the old world
monkey with rudiments of two posterior cusps and a rudimentary anterior One and a subsidiary small cusp
between the outer main two cusps.
The Bushman tooth is not very unlike that of Paranthropus, but is less worn. It shows a distinct small
antero-external cusp on the front of tIie outer side, ~nd a little fovea on its inner side. It is interesting to
note the similarity of this little fovea with the one in th~ baboon tooth. Near the middle of the inner side
of the tooth is a well-marked shallow depressioI) in place of the transverse groove in most teeth. This
probably corresponds to the marked depression in the baboon's tooth. _
It is unfortunate that, so far as we are aware, no upper milk molar teeth has even been found in any
fossil Primate except Plesianthropus transvaalensis, not even in Pekin man. We thus cannot make !llany
comparisons. The Plesianthropus tooth was figured in our previous Memoir. on Plesianthropus. The
Plesianthropus tooth is much less worn, but agrees rather closely with that of Paranthropus. There is in it
a distinct Carabelli cusp, and not improbably there had been a small cusp on the anterior and outer corner
of the tooth.
82
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SWA'RTKMNS . APE~MAN
83
Though we know only one tooth of the vpper deciduous dentition of Paranthropus,we forturiately
whole ofJhe lower set quite satisfactorily.. We have two child jaws, one with all the milk teeth.
hut wi~h the incisors crushed backward; the other, with three of the milk incisors lost, but with the canine~
a~d milk molars preserved. Probably one jaw is th~tof a·male and the other that of a female.
In the larger jaw, which is presumably male, the four milk incisors are preserved but the crownS have all
been crushed back and broken at their bases. They now lie in a row between the canines. The buccal
surfaces of the crowns, so far as can be seen, do not differ much from those of man. The lingual surfaces
are less satisfactorily seen than the buccal. The central incisors are smaller than those of the Bushman.
The crownS of the two together have heen about 7·5 mm. The lateral incisors have been considerably
larger tha~ the central and the crowns of the four have measured about 18 mm. Fr6m the inner (lingual)
side to the outer,· the crown 9f the right second milk incisor measures about 6 mm., and from the lower
part of the lingual surface to the lower part of the buccal the measurement is about 5 mm. The height
of tlie crown has been about 10·2 mm. The crowns are thus a little narrower than in the Bushman and very
distinctly higher. As thetopsof'the crowns are appreciably worn, we cannot say if the shape of the top of
the crown is as in man-probably it was flatter.
.
Both canines are well-preserved, but a little worn. Antero-posteriorly the right crown measures
6·3 mm. and the width of the tooth is 6·2 mm. The left tooth measures in length 6· 1 mm. and in width
5·8 mm. The height of the left crown, as preserved, is 7·5 mm. Before being worn it w~s probably
:9'5 mm. The height of the right canine was probably about the same.
/
The crown of the canine has two very distinct cusps. The anterior or main cusps form about three.quarters of the tooth, and the posterior about a quarter. There is no indication of there having been an
anterior cusp as in Plesianthropus. Between the two cusps, on both the lingual and buccal surfaces, there
is a well-marked vertical groove. The width between the two canines is 15·9 mm. The width between the
canines in a Bushman child jaw is 18' 5 mm. In a chimpanzee child jaw, that lies on our desk, the
.
corresponding measurement is 21' 7 mm.
The first deciduous molar is beautifully preserved on both sides of this male child mandible and, though
considerably worn, the flat surface has lost little more than the upper parts of the four main cusps. The
right crown is a little less worn than the left. It may be described as formed by four subequal cusps, with
two very small posterior cusps and a small antero-external one. On the buccal side there are the remain.~
of a groove between the two main outer cusps, and across the outer and lower part of this groove is a ledge
of eriamel formed by the cingulum, and on the right tooth there is a very small cusplet on this little enamel
ledge.
On the front of the tooth there is a well-marked fovea, which stretches across about a third of the tooth.
The two main anterior cusp~ occupy about the anterior half of the crown, except for the very small extra
cusp in the anterior outer conner. Posteriorly, the third and fourth cusps, and the two small posterior cusps.
.
.
occupy the posterior half of ~he tooth.
The following are the 4easurements of the first lower deciduous molars in the Swartki"ans ape-man.
In.one jaw they are 11·1 mrrl.. by 9'4 mm. and 11·1 mm. by 9·4 mm. In the other 11·8 mm. by 9·4 mm.
and 10·4 mm. by 8·3 mm. \
.
We have argued in vari9us papers that' this type of tooth, with four large subequal cusps, is probably
the ancestral type from which the type of tooth found in modern anthropoids was derived by the antero":
external cusp becoming enlarged and the others reduced. Even in the gibbons, which probably branched
off from the main anthropoid stem as early as Lower Oligocene, we firid practically a unicusped milk anterior
molar. It is a cutting tooth with only one large, pointed cusp, which is. clearly the antero-external and a
trace of what is probably the postero-external. Almost exactly the same type of tooth is found in the
gorilla. In the chimpanzee we have a toothl,essentially like that of the gorilla, but differing in retaining a
somewhat reduced antero-internal cusp close Ipn the side of the main cusp and usually rudiments of the two
posterior cusps and of the small anterior. In; the orang the tooth is very similar to that in the chimpanzee.
but is a little more primitive in the antero-i~ternal cusp being a little more separated from the anteriorexternal and iIi having the posterior cusps a little better developed. But in all orang teeth we have seen, or
of which we have figures; the antero-external ,<lisp is·always the main cusp: '.
'
know~the
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84
SWART KRANS
APE~MAN
lit the baboon, Cercopithecus,. Colobus and probably all old world monkeys the first lower milk molar
is a rather narrow five-cusped·tooth.·There is, however, a considerable degree of variation in.the different
:genera, 'and so far· as we are aware no one has.ever made much 'study of the milk dentition of ihe old world
morikeys, and.it is impossible for us in South Mrica, with our very limited collections 'of Asiatic monkeys1
skulls; to do so. Th~.work mus't be done in one of the large museums of Europe. or America.
A
FIG. 48.-Milk dentition of lower jaw of three Primates.
A. Paranthropus crassidens, probably male.
B. Gorilla (from Emil Selenka, after Rose).
C. Chimpanzee, Pan sp.
(All figures twice natural size.)
No doubt, most scientists will hesitate about accepting the evidence afforded by one tooth, and that a
deciduous one, that the higher Primates early divided into two main branches-one the branch which has
resulted in all the known anthropoids living and fossil, with the possible exception of the gibbons, and
another branch which led on to man, possibly through what \\Ie call the ape-man of South Africa. Still,
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SWARTKRANS-APE-MAN
85
we'think that'iltis'fust lower milk molar does s~gest this early separation of the human line and the ape line.
And there are, many other facts which seem to point in, the same direction. Further, where much of the
evidence seen,ls r~ther equivocal, one is glad to have even a straw that seems to give us some useful guidance~
The seCond lower deciduous molar ~~ also interesting. The examples we have of it are essentially
similar. Asthe teeth of both sides arepresent'in both jaws we have really four examples. In the one jaw
they measure 13·5 mm. by 12·2 mm. and 13·3 mm~ ,by 12·0 mm. In the other jaw the teeth measure
13'·9 mm. by)2·4 mm. and 13·8mm. b,y 11·2 mm;' Th~se are not so long as in the gorilla, but much wider.
G
'.
...
I
I
'
A
.B
J
C
deci~uous
.D
(]
0
0
r;
°
F
vario~s
FIG. :.-Dental
patte: I right lower
molars of
.
A. Baboon, Papio ursinus.
H.
B .. Orang-outang, Pongo sp.
I.
C. Chimpanzee, Pan sp.
J.
D. Chimpanzee, Pan sp. (after Selenka).
K.
E. Gibbon, Hylobates concolor (after Rose).
F. Gorilla, Gorilla gorilla (after Rose).'
L.
G. Kromdraai Ape-man, Paranthropus robust us.
Primates. (All t:ce natural size.) L
Swartkrans Ape-man, Paranthropus crassidens.
Swartkrans Ape-man, Paranthropus crassidens.
Taungs Ape-man, Australopithecus africanus.
Sterkfonteiri Ape-man, Plesianthropus transvaalensis.
Bushman, Homo sapiens'.
The crown may be described as consisting of three large outer cusps and two large inner, with a small
sixth cusp behind the two main posterior cusps. Across, near the front of the tooth, is a well-developed
anterior fovea. On the buccal side of the tdoth are two marked pits formed by the cingulum, and in one of
the four teeth there are two tiny cusps outside the pits.
In Fig. 49 we have given for compari~on ocClusal views of the right lower milk molars in various
i
Primates.
A represents ,the milk molars of the common baboon. Here the anterior tooth is seen to have four
sube,qual cusps, with a small anterior cusp. 1;his seems to he the pattern in all the old world monkeys. The
7.
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·86.
SWARTKRANS APE-MA:~
posterior topth is essentiillly.similar with four main cusps and ~ .fifth near. the middle line b~hind tp.e
posterior two main cusps. .
B, C,D,E and F show the,arrangement of the cusps in living' anthropoids. B, are'the teeth of the
orang. The anterior tooth is narrow. Near the middle of the tooth is' a large cusp which is the ahteroexternal cu~p of the baboon, and' rather close to it, but quite distinct, is the antero~internal cusp; -It is l!.
little smaller than the other but appears to be always close to it. :posteriorly,there is a rudiment of the
. postero-external, and possibly there isa rudiment of the postero.,int'ernaL In front there is -li smap ant~rior
cusp. We are probably right in assuming that this tooth has evolved from a tooth like. that found in the
baboon, by the increase in development of the main anterior two cusps and their approximation to each
other, as the first step in. the evolution of the tooth from a molariform tooth to a cutting one., The
posterior milk molar in the orang has five cusps as in the baboon, but the cusps are differently shaped.
In th~. chimpanzee (C and D) we have the antero-external cusp a little better developed than in the
orang, and the antero-internal relatively a little less developed and closer to the main cusp. Posteriorly,
there is usually a rudiment of the postero-external cusp in unworn teeth, and sometimes a: rudiment of the
postero~internal. In unworn teeth there is generally a ver"y smail anterior cusp. '.'
.
The posterior deciduous molar is fairly similar to that in the orang. There an~ five well-developed
cusps and occasionally a very small anterior cusp in front of the main antero-external. In the gorilla (F) we seem to have the last stage in the evolution, which has been well initiatedjn the
orang and chimpanzee. The anterior deciduous molar has now lost almost all trace of the original molari~ .
form tooth, and has now only one large pointed main cusp which is the antero-external. All trace of the
antero-internal is gone. Of course only a very limited number of baby gorilla ja~s have been exami~ed and
quite possibly if a few hundred were examined, one might show evidence of an antero-iritemal cusp as an
abnormality. So far as we know, such a cusp has not been described. There is usually evidence of a small
anterior cusp on the very front of the tooth. The whole tooth is about twice as long as broad, and it is as
much a cutting premolar as are the premolars of carnivores. The posterior deciduous molar is very large
and, though a molariform tooth with five well-developed cusps, it is, like the anterior tooth, nearly twice as
long as broad.
The little gibbons (E) have deciduous molars fairly similar to those of the gorilla, but very--small. The
anterior tooth has only one main cusp and a trace of the postero-external. The posterior tooth'has five
cusps, as in the other anthropoids and baboons. Possibly the gibbons have evolved a cutting anterior tooth
independently of the line which led to the gorilla.
In Fig. 49 we show the deciduous lower molars of the ape-men, in which they are known, and of
man. If these six drawings are examined and compared with the drawings of the anthropoid teeth above
them, it wiiI be seen that the teeth of the ape~men and of man all differ very markedly-so markedly that
we feel compelled to reject the generally accepted view that man has come from an anthropoid ape such as
the chimpanzee or gorilla, and has probably come along with the ape-man from a very early anthropoid
or possibly a pre-anthropoid ancestor.
The evolution of the anterior deciduous molar is very interesting. In the Kromdraai ape-man (G) we
see five subequal low rounded cusps-very unlike anything seen in any known anthropoid. There is a
well-developed fovea in front. In the allied Swartkrans ape-man, as seen in H and I, there are one or two
differences. There is it little anterior cusp and with its development th.e fovea is shifted a little towards the
inner side, and the fifth posterior cusp is reduced-of course it may be that this is the more primitive stage
and that seen in the Kromdraai ape-man the later stage. Each is manifestly an early stage.
When we examine this first deciduous molar in the Taungs ape-man and the Sterkfontein we find what
is manifestly a later stage. Here the anterior cusp is in the middle of the front of the tooth and the anterior
fovea is pushed round to the lingual side of the tooth. The human tooth, as seen in the Bushman, is almost
e~actly like that of the Taungs ape-man. Of course, we have many races of man, and in many the teeth
have become reduced and degenerate, and as might be expected there is considerable variation; and it may
be that among the degenerate teeth there may be found a few a little like those found in the chimpanzee. But
we do not think a human tooth has ever been found at all like that of the gorilla. And as teeth, almost
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SWARTKRANS APE-MAN
87
identical with those of the Taungs ape-man, are found in primitive human types, we feel justified in
believing that man must be related much moren~riy to the Taungs and Sterkfontein ape-men than to any,
of the known anthropoids. The structure of the first lower milk premolar, in man is quite a remarkable
specialisation, ,and it is unlikely that such a 'specialisation could have developed twice independently. And
it seems hardly possible that, if man came from an ancestor like the chimpanzee or gorilla and had ancestors
wjth teeth like those of the anthropoids, he should later have evolved teeth like those of the Taungs ape-man
from teeth like those of the chimpanzee or gorilla.'
,
The posteri~r dedduous molar teeth of the ape-man and man are nearly as instruCtive. If the series
pf six teeth be examined and compared with those of the ~nthropoids two remarkable points of difference
are manit~st. The artthropoid teeth are all much longer than broad: the ape-man and human teeth are all
nearly as broad as long: Further, while ~ll the known ape-men teeth have six cusps, apart from rudimentary
ones, and,even the Bushman has no~ma:lly SIX cusps, the anthropoids never seem to have more than five cusps.
, We think the figures we give will convinCe most anthropologists that the milk molars of the ape-man
are not very like those oHhe anthropoids, in either structure'size or indices, 'and that they resemble those of
Dian rather closely. '
.
.'
,",.
;,