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Anatomical and functional specializations of the human gluteus maximus.

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Anatomical and Functional Specializations of the
Human Gluteus Maximus 1
JACK T . STERN, J R .
D e p a r t m e n t of A n a t o m y , University of Chicago, Chicago, Illinois 60637
K E Y WORDS
Locomotion.
Primates . Evolution . Morphology . Muscles
.
ABSTRACT
Many anthropologists and anatomists have claimed that the
human gluteus maximus is a functionally and structurally unique muscle,
but there is not agreement on the actual characteristics of the muscle which
do distinguish man from other primates. In this paper the superficial gluteus
in a wide range of primates is discussed and those traits entirely unique to
man are identified. The morphological specializations of the human gluteus maximus are confined to its cranial portion. This part is thicker in man than in any
other primate; i t has a new and firm origin, a modified ascending tendon of
insertion, and an additional new insertion into the overlying fascia lata. Such
changes improve the ability of the gluteus maximus to participate in controlling
lateral stability of the trunk, and it suggested that this is the function which
has been selected for in human evolution.
Scarcely a n author exists who has written on the hip muscles of primates and
failed to place great emphasis on the
unique nature of the human gluteus maximus. This muscle is considered by most
to be a hallmark of bipedality. It was
noted very early that the most sperficial
of the gluteal muscles was relatively much
larger in man than in non-human primates, and there is frequent comment
that the adjective “maximus” can be accurately applied to the muscle in no primate other than man. However, the bulk
of the human superficial gluteus, as indicative as i t is of uniqueness, should
mainly provide us with the incentive to
investigate the situation more closely.
This has been done from time to time,
with the surprising result that there is
neither a general consensus on how the
function of this muscle differs between
man and the lower primates nor even a n
accurate description of those structural
characteristics of the muscle which are
distinctly human.
Our story begins, as do so many in comparative primate morphology, with Edward
Tyson (1699). In the first authenticated
dissection of a n anthropoid ape, the chimpanzee, he observed (p. 89):
A M . J. PHYS. ANTHROP., 36; 315-340.
The muscles of n o part disagreed so much
from those i n M e n , a s those of the T h i g h
of this A n i m n l . Here was 110 Glutezis mino,-; nor did the Glziteus m a s i r n u s resemble the H u m a n e : It was merely T e n d i n o u s
at its Origin, from the whole Spine of the
0 s I l i u m ; it was much longer, a n d not so
thick a s i n Man.
Tyson did not speculate on the functional significance of these differences;
indeed, he believed that his “pygmie” was
probably a biped in its natural environment. Over a century later, Trail1 (1818)
agreed that the glutei of the chimpanzee
differed much in form from those in man.
The externus was very thin and did not
come as far forward, nor did it arise from
so large a portion of the ilium.
Cuvier (1835) introduced a functional
explanation for the differences between
man and non-human primates with regard
to the superficial gluteus. He attributed
the considerable size and strength of the
muscle in m a n to the need for preventing
flexion of the trunk under its own weight
during standing or during the stance
phase of walking, However, Cuvier called
attention to the fact that the gluteus
1 Several of the author’s ideas discussed in this
paper were presented to the American Association of
Anatomists (Chicago, ’ 7 0 ) and appear in abstract form
in the Anat. Rec., 166: 384, 1970.
31 5
316
JACK T. STERN, JR.
superficialis of “singes” has a n extensive
femoral insertion compared to that of man,
and he concluded that, as a result of this
distal attachment, the muscle perhaps
has a n action as powerful as in man.
Later, Laurillard (Cuvier and Laurillard,
1849) expanded on his colleague’s speculation by stating that a long femoral insertion of the gluteus superficialis, as
seen in the black lemur, endows this animal with a remarkable agility for leaping.
Burdach (1838) arrived at quite a different assessment based on a comparison
of man to Old World monkeys. He suggested that the action of the gluteal
muscles was not the same in these two
forms. Burdach emphasized the ability of
the human gluteal musculature to rotate
the thigh, a n action he believed to be very
important in bipedal standing and walking. It was his opinion that in monkeys
retraction, not rotation, is effected by the
gluteal muscles.
In what may be considered the first
primarily functional investigation of primate myology, Wilder (1861) discounted
the importance of the differences in size
of the glutei between man and the Quadrumana. The real distinction, he asserted,
is in the position of these muscles. In
man the gluteus maximus does not arise
from the ischium and lies equally above
and below the center of motion of the hip.
In the Quadrumana the muscle arises
chiefly from the ischial tuberosities (as
we shall see, this is true only in some
apes) and inserts much lower on the femur. Although in both forms the superficial gluteus is a n extensor of the thigh,
only in m a n is it able to bring the lower
limb in line with the trunk and can therefore act with the gluteus medius and
psoas “in preserving the balance forward
and backward, which is also required in
ordinary progression” (p. 372). In the ape,
suggested Wilder, this muscle is a powerful retractor of the whole limb and acts
with the gluteus medius i n leaping. Alone,
the gluteus superficialis would rotate the
thigh outward so as to turn the sole of
the foot inward, after which it would assist the adductors i n keeping the foot
close against the object grasped in climbing.
Both Bischoff (1870, 1880) and Primrose (1898-1899). supported the views of
earlier authors that the giuteus superficidis of apes is a powerful extensor of
the thigh, but instead of postulating that
this is most functional in leaping, they
emphasized a role for the muscle in producing retraction of the limb in climbing.
Wiedersheim (1895), though acknowledging the large size and great strength of
the human gluteus maximus, agreed with
Cuvier and Wilder that the muscle served
mainly to steady the trunk on the heads
of the femora.
In general, the authors of the nineteenth century saw the superficial gluteus as a n extensor in both man and
non-human primates, the distinction being
that in m a n the gluteus maximus plays
an essential role i n antero-posterior balance, whereas in other primates the muscle functions chiefly in either the leaping
or climbing modes of locomotion.
An entirely different approach to the
problem was initiated by Klaatsch (‘13).
He proposed that the gluteus maximus
is a climbing-muscle of the first order,
but only in the human manner, this
being climbing large vertical tree trunks.
Klaatsch believed that such a manner of
climbing was preadaptive to erect bipedality. The suggestion that the gluteus maximus be considered a uniquely powerful
extensor in m a n carrried over to Waterman (‘29). She concluded that the new
and firm attachment to the ilium, taken
in connection with the sacral origin, enables the muscle to act with power in
lifting the trunk from the stooping position. According to Waterman, in monkeys
and apes the superficial gluteus is a n
abductor and relatively much weaker.
From Boyer (‘35) came the statement that
in the orang-utan the primary action of
the gluteus superficialis is abduction, not
extension as in man. The trend toward
asserting that extension of the thigh is a
special function in man continued with
Kleinschmidt (‘49, ’51) and reached its
culmination with Washburn (‘51). According to Washburn, the critical changes in
the evolution of erect posture were those
in the ilium and gluteus maximus which
converted the latter from a n abductor i n
apes to a muscle which is able to complete
the powerful extension of the hindlimb
necessary in walking (the emphasis on
completing extension harkens- back to
SPECIALIZATIONS OF HUMAN GLUTEUS MAXIMUS
Wilder). This view has been widely adopted
(Tappen, ’55; Breitinger, ’59; Robinson,
’63; Campbell, ’66; Snyder, ’67; Le Gros
Clark, ’67).
Howell (‘59) agreed that the superficial
gluteus has evolved into a powerful extensor in man, but he suggested that in
apes and monkeys it functioned in lateral
rotation (a view exactly opposite to that
held by Burdach). To Buettner-Janusch
(‘66) the extensor action of the gluteus
maximus is important more especially for
such activities as running, walking up an
incline, or climbing stairs, but he did
point to a function in bipedal locomotion
generally. Napier (‘67) holds a similar
view, but specifically discounts the action
of the muscle during walking on a level
surface.
Thus, in the course of half a century,
the opinion that the superficial gluteus
is a powerful extensor acting during locomotion in lower primates, but suited to
more refined tasks in man, has been
nearly reversed.
Not all recent authors adopt what is
the prevailing modern view outlined above.
Dart (‘49) emphasizes the rotatory functions of the gluteus maximus, as did
Burdach. More recently, Sigmon and Robinson (‘67) claim that there are no major
differences in function of this muscle in
apes and man. Robinson (‘68) combines
aspects of old and new by concluding
that the muscle is a powerful extensor in
both groups, but is not able to complete
extension in apes. However, he states that
the chief importance of the gluteus maximus in man is not during walking but in
the more strenuous activities of running,
climbing, and rising. Sigmon (‘71) adds
that the gluteus maximus in upright bipeds is more of a speed-of-action muscle
compared to that of apes.
It is my belief that although elements
of truth are contained in a number of the
theories proposed to date, the major morphological and functional distinctions between man and non-human primates with
regard to the superficial gluteus have not
been identified. It is the plan of this paper
to determine more carefully how the structure of this muscle differs among primates
and to identify those traits entirely unique
to man. The results of such an analysis
will be correlated with evidence bearing
317
on the function of the gluteus maximus
in order to arrive at a new conclusion
about the special role of the muscle in the
evolution of human locomotion.
MATERIALS AND METHODS
Observations on the attachments and
structure of the gluteus superficialis were
made on the following non-human primates (number of specimens in parentheses): Lemur mongoz, mongoose lemur
(1); Lemur fulvus, brown lemur ( 2 ) ; Microcebus murinus, lesser mouse lemur
(1); Cheirogaleus major, greater dwarf lemur (1); Propithecus uerreauxi, Verraux’s sifaka (1); Nycticebus sp., slow
loris (1); Perodicticus potto, potto (1);
Galago senegalensis, bushbaby (1); Galago
demidovii, dwarf galago (1); Tarsius syrichta, philippine tarsier (1); Saguinus nigrocollis, black and red tamarin (1); Callicebus, titi (6); Aotus, owl monkey ( 7 ) ;
Saimiri, squirrel monkey (6); Cebus, capuchin ( 7 ) ; Cacajao, uakari ( 6 ) ; Pithecia,
s a h (5); Chiropotes, bearded saki (1);
Alouatta, howling monkey (10); Lagothrix,
woolly monkey ( 6 ) ; Ateles, spider monkey
(6); Cercopithecus aethiops, grivet (1);
Macaca mulatta, rhesus monkey (2);
Theropithecus gelada, gelada baboon (1);
Mandrillus sphinx, mandrill (1); Hylobates lar, white-handed gibbon (1); Symphalangus syndactylus, siamang ( 2 ) ; Pongo
pygmaeus, orang-utan (3); Pan troglodytes,
chimpanzee (1); Gorilla gorilla, gorilla (1).
Quantification of the level of insertion
into the femur was performed on ceboids Hylobates, Symphalangus, Pan, and
two specimens of Pongo. The technique is
described by Stern (‘71).
Careful dissection and quantification of
insertion of the gluteus maximus was
undertaken for two human fetuses (third
trimester), and six adult humans. More
general confirmatory observations were
made on 40 human cadavers used over
the last two years in the medical gross
anatomy course at the University of Chicago.
An excellent review (with some original data) of the myology of the hip and
thigh in Old World primates has recently
been published by Uhlmann (‘68). How2 More detailed information on the specimens of New
World monkeys can be found in Stern (’71).
318
JACK T. STERN, JR.
ever, I believe it is necessary to summarize below the structure of the gluteus
superficialis i n non-human primates, especially because my approach is different
from Uhlmann’s and I can add extensive
personal observations. Much of what is
presented is gathered from the literature.
In order to conserve space, specific citations will be made only in special cases.
However, almost all the references listed
by Uhlmann have been personally reviewed
by me, and the descriptions which follow
are based on this review.
RESULTS
The “primitive” state
There is a basic configuration of the
gluteus superficialis common to all prosimians, callithricids, and the more strictly quadrupedal cebids. To this extent, at
least, such a configuration may be considered primitive. There is no direct evidence that it was present in any or all
ancestral primates, but its distribution in
living forms leads one to this supposition.
The “primitive” gluteus superficialis is
a flat muscle more or less in the shape of
a triangle, the base of which is represented by the origin and the apex by the
distal point of the insertion (plate 1,A).
In the quadrupedal position the hip joint
is deeply located approximately a t the middle of the triangle.
The gluteus superficialis arises anteriorly from the strengthened fascia covering the gluteus medius. The extent of this
attachment is variable. From the gluteal
fascia, the origin passes dorso-caudally
to the fascia over the tail muscles and
then travels caudally along this fascia up
to the region of the first few caudal vertebrae, from the transverse processes of
which a considerable portion of the muscle directly arises.
The “primitive” gluteus superficialis
inserts entirely into the femur. The anterior (cranial) half of the muscle goes to a
tendon which forms on its deep surface
and in turn attaches to the caudo-lateral
surface of the femur just below the greater trochanter (plate 2A,B). In prosimians,
the attachment area is marked by a well
defined third trochanter, and there is a n
elevation of less marked prominence in
other forms. The tendon of insertion of
the anterior portion of the muscle is called
the ascending tendon (Stern, ’71) because
its anterior fibers insert most distally,
while the more posterior ones attach progressively higher on the femur. The distal
edge of the tendon is located at the site
where the fascia covering the gluteus
superficialis passes distally into the fascia
femoris. As a result, it can appear that
the anterior fibers of the muscle insert
into the fascia femoris, but this quite definitely is not the case.
The caudal portion of the “primitive”
gluteus superficialis inserts either directly, or by means of a flat tendon, or by
both means, into the posterior surface of
the femur from the level of the ascending
tendon (or a bit more distally) to well past
the middle of the bone. The most anterior
fibers of this portion insert proximally,
the more posterior fibers attaching progressively further down the shaft. When
the caudal portion has a well formed tendon, its lateral edge is attached to the
fascia femoris. However, the tendon fibers
do not pass into the fascia femoris, but,
on the contrary, proceed to the femur.
Primitively, the anterior portion of the
gluteus superficialis is very thin, while
the posterior portion, particularly the fibers arising from the caudal vertebrae,
is thick and seemingly powerful (plate
3,A,C,D). In some cases the division into
two portions is not merely topographical;
the insertion of the ascending tendon may
be quite separate from the remainder of
the femoral attachment, and division here
can often be carried proximally with very
little difficulty. The significance of this is
moot.
The descriptions of the gluteus superficialis that follow attempt to point out
briefly more particular aspects of the
structure of this muscle i n primate subgroupings. Emphasis will be placed on
deviation from the “primitive” condition.
Prosimians
Among the Lemuroidea, Daubentonin,
the Galaginae, and Tursius, the structure
of the gluteus superficialis is nearly uniform and agrees closely with what has
been described as the “primitive” state. In
all these forms the gluteus superficialis is
SPECIALIZATIONS OF HUMAN GLUTEUS MAXIMUS
319
in close connection with the tensor fasciae been described a small attachment to a
femoris, which inserts into the ascending lateral intermuscular septum (Bluntschli,
tendon and a tendon fused to it. There is ’13) or fascia femoris (Uhlmann, ’68). In
variable evidence of a separation between my specimen of L. mongoz a tendon was
the two muscles. Fibers arising from associated with the more proximally inthe anterior superior angle of the ilium serting fibers of the caudal portion of the
sometimes appear to form a distinct bun- muscle, however, I can confirm the finddle which is called tensor fasciae femoris. ings of most authors who report no true
These fibers are innervated by the superi- fascia1 insertion in the genus Lemur.
or gluteal nerve, but in Lemur, Bluntschli
The posterior fibers of the gluteus su(‘13) and Uhlmann (‘68) found that the perficialis are said to extend their insersuperior gluteal nerve also supplied most tion onto the capsule of the knee and
of the fibers arising from the gluteal tibia1 tuberosity in cheirogalienes (Juoffascia. Whether these fibers ought to be froy, ’62). I did not observe this, but I did
assigned to the tensor fasciae femoris note that the femoral attachment con(thus leaving us with a gluteus super- tinues further distally than in other proficialis characterized by a very slight or simians, reaching the lateral condyle and
absent origin from the gluteal fascia) or sesamoid of the lateral head of gastrocbe considered as belonging to the gluteus nemius. In lemurines and Daubentonia
superficialis but having an “anomalous” the posterior fibers of the gluteus superinnervation (as I believe occurs in some ficialis fall just short of the lateral concebids, Stern, ’71), cannot as yet be de- dyle, and a lesser area of insertion occurs
termined. In the specimen of Propithecus in indriids. Juoffroy (‘62) stated that the
available to me (Field Museum of Natu- distal limit of the femoral attachment in
ral History 85150), there occurred an Propithecus was two-thirds the way down
easily separable tensor fasciae femoris the bone, but in my specimen the muscle
arising from the anterior superior iliac reached from three-fourths to four-fifths
angle, the septum intermusculare iliacum, down the femur (plate 3,A). Milne Edand adjacent gluteal fascia. It was inner- wards (1875) reported that in Avahi the
vated by the superior gluteal nerve, which gluteus superficialis does not insert bedid not send branches to fibers of the yond the femoral midpoint. Galagines and
gluteus superficialis arising from the glu- Tarsius resemble the Indriidae in that the
teal fascia. Also in Tarsius, the tensor insertion is generally limited to the upper
fasciae femoris is well separated from the two-thirds of the femur.
In Lemur (Lucae, 1884; Appleton, ’21),
gluteus superficialis at their origins.
In lemuroids, Daubentonia, galagines, Daubentonia (Lucae, 1884), and Tarsius
and Tarsius, the origin of the gluteus (Appleton, ’21), the weight of the comsuperficialis from the tail encompasses bined gluteus superficialis and tensor fasthe first two, or more usually the first ciae femoris exceeds that of either of the
three, caudal vertebrae. The origin here other two gluteal muscles. Ranke (1897)
is largely by muscular fibers, though I stated that the gluteus superficialis was
observed short tendons in Lemur, Propi- stronger than the medius in Lemur. The
thecus, and Tarsius. Galagines differ from posterior portion of the gluteus superficithe other mentioned forms in having a di- alis is markedly thicker than the anterior
rect muscular origin from the iliac crest portion in lemuroids (plate 3,A). I found
(plate 1,A) as opposed to an origin medi- the difference in thickness to be less obviated by the gluteal fascia. Once again, ous in Galago, and not at all noticeable in
however, these fibers probably represent Tarsius. However, the tarsier possesses a
tensor fasciae femoris. Murie and Mivart powerful caudo-femoralis running along(1872) reported that they inserted into side the posterior portion of gluteus superthe fascia femoris in one of their speci- ficialis and, no doubt, having a very similar action.
mens of G. crassicaudata.
Among lorises the gluteus superficialis
In the four groups of prosimians under
discussion, the posterior portion of the differs in some rather important ways
gluteus superficialis inserts muscularly from that in the previously described prointo the femur. Only in Lemur has there simians. In the Asian forms there is no
320
JACK T. STERN, JR.
muscular bundle arising either tendinously or muscularly from the anterior superior iliac angle or ventral third of the
iliac crest. Instead there is a direct muscular origin from the dorsal portion of
the iliac crest. These fibers appear to correspond to a tensor fasciae femoris; they
are innervated by the superior gluteal
nerve (Bluntschli, ’13). Perodicticus is
similar to most other prosimians in that
muscular fibers arise from the anterior
superior angle of the ilium and caudal to
this from the gluteal fascia.
Bluntschli (’13) reported that in Nycticebus muscular fibers arise from the dorsal edge of the ilium. They were innervated by the superior gluteal nerve and
possibly could represent a portion of the
tensor fasciae femoris. However, I very
carefully looked for fibers arising directly
from the dorsal edge of the ilium in three
specimens of Nycticebus and found no
such origin.
The gluteus superficialis arises from
caudal vertebrae one to three in Nycticebus (Bluntschli, ’13). Juoffroy (’62) has
reported the same for the potto, but
Riska (’36) and Uhlmann (’68) state that
the origin also encompasses the fourth
and fifth caudal vertebrae in Perodicticus.
The latter two authors note that the caudal origin in Perodicticus is tendinous,
and my observations agree. A similar tendinous origin occurs in Nycticebus.
Appleton (‘27) reported that in both
Loris and Perodictius, but not in Nycticebus, the gluteus superficialis extends its
origin to the ischial tuberosity with the
formation of a fibrous arcade which he
calls a sacro-tuberous ligament. Riska
(‘36) noted that in most of his specimens
of lorises the posterior portion of the gluteus superficialis either covered or had a
small origin from the ischial tuberosity.
He stated that only in these forms and
man was the ischial tuberosity covered by
this muscle. However, both Uhlmann (‘68)
and I found this relationship in Lemur,
and I also observed it i n the other lemuroids. An actual origin from the tuberosity
is quite a different matter. Uhlmann (‘68)
confirms Appleton’s observation that it
occurs i n the potto, but Nayak (cited in
Juoffroy, ’62) disputes its presence in
Loris. No such origin occurred in my
specimen of Perodicticus, but i n both this
genus and Nycticebus the tendon of origin
did adhere strongly to the fibrous tissue
over the ischial tuberosity.
As in all prosimians, the ascending tendon attaches to a narrow region high on
the femur, from 5%-1 1% down the shaft
in my specimen of slow loris. The insertion of the posterior portion of the gluteus superficialis nearly reaches the lateral femoral condyle in lorises. It differs
substantially from the condition i n other
prosimians in that there is a tendon of
insertion which also gives origin to fibers
of the vastus lateralis (and possibly vastus
intermedius). Thus a true lateral intermuscular septum is formed. I should emphasize that observations bearing on this
point exist only for Nycticebus and Perodicticus (Bluntschi, ’13; Uhlmann, ’68;
and personal data).
N e w World monkeys
A detailed description of the gluteus
superficialis in cebids can be found in
Stern (‘71). The marmosets resemble Callicebus.
The structure of the gluteus superficialis in marmosets and all cebids exclusive of Alouatta and the Atelinae follows closely the primitive pattern. The
extent of origin from the gluteal fascia is
variable (slight in marmosets, Callicebus,
and Pithecia; moderate in Saimiri, Cebus,
Chiropotes, and some specimens of Cacajao; extensive in Aotus and the other specimens of uakari). There is a fair degree
of interindividual variation in the number
of caudal vertebrae giving rise to the
posterior portion of the gluteus superficialis, but usually the first two or three
are involved, with the fourth coming into
play often in Saimiri and Cacajao (in this
latter form caudal vertebrae may be incorporated into the sacrum).
The ascending tendon inserts into a
short region high upon the femur in those
ceboids characterized by a “primitive”
gluteus superficialis (plate 2,B). In Callicebus, Aotus, Cacajao, and Pithecia the
attachment is from 6%-11% down the
femur; it lies 1 or 2% further distally in
Saimiri and Cebus.
In New World monkeys the posterior
portion of the gluteus superficialis inserts
largely by means of a tendon, best devel-
SPECIALIZATIONS OF H U M A N G L U T E U S MAXIMUS
oped in the larger forms. The muscular
fibers continue about half-way down the
thigh in Callicebus, Aotus, and Saimiri
(plate 2,B); the tendon extends the attachment three-fifths down. In Cacajao,
Chiropotes, Pithecia, and Cebus, the flesh
reaches about two-fifths the way down the
femur, and the tendon ends somewhat
beyond the midpoint. Therefore, there is
a less extensive femoral insertion in “primitive” New World monkeys than occurs
in almost all prosimians.
Alouatta caraya possesses a gluteus
superficialis which differs from the “primitive” state by possessing a wider, stronger, and more distally inserting ascending
tendon, and a posterior portion whose
tendon of insertion is lightly fused to the
aponeurosis of origin of the vastus lateralis. The muscular fibers extend about
as far down the thigh as in the uakari
or capuchin. In Alouatta palliata, there
are several additional differences. A well
defined tubero-caudal ligament occurs,
and from its external surface fibers of the
gluteus superficialis arise. The posterior
portion of the muscle descends no further than one-third the way down the
thigh. It inserts onto the back of the
ascending tendon and also via a clearly
developed lateral intermuscular septum.
In the woolly monkey no tubero-caudal
ligament exists, but the origin from caudal vertebrae is tendinous, and in most
specimens this tendon extends toward the
ischial tuberosity, sometimes nearly reaching it. The ascending tendon is well
developed and inserts from 14% to 21%
down the femur, whereas the posterior
portion of the muscle has the same manner and extent of attachment as occurs
in A. palliata.
The gluteus superficialis of Ateles deviates very markedly from the “primitive”
state. There is a well developed caudal
tendon of origin which always extends up
to, though not actually reaching the ischial tuberosity. Furthermore, the origin
from the tail does not go beyond the second caudal vertebra, and occasionally not
beyond the first. The powerful ascending
tendon (plate 3,B) attaches from 15% to
24% down the femur. The posterior portion of the muscle inserts almost wholly
into the back of the ascending tendon,
never extending far below it. There is
321
less distinction between the thicknesses
of the caudal and cranial portions of the
gluteus superficialis (plate 3,B) but the
former remains the thicker. In its shape
and localized insertion, the muscle presents an appearance similar to the deltoid
of the shoulder.
I have weighed muscles in one specimen of each cebid genus (Chiropotes and
Brachyteles excluded). In Saimiri the gluteus superficialis weighed slightly more
than the medius. The medius was not
much heavier than the superficialis in
Cebus. In other forms the predominance
of the medius was substantial, particularly
so in the ateline genera.
Old World monkeys
The gluteus superficialis differs more
from the “primitive” state in Old World
monkeys than in any other primate group.
Furthermore, Klaatsch (‘00) remarked
that all Old World monkeys are alike with
regard to the configuration of the muscles
on the outer part of the thigh, and a review of the literature coupled with my
own observations leads me to agree. The
only point wherein one form may differ
significantly from another is in the presence or absence of an origin from a
sacro-tuberous ligament and/or ischial
tuberosity. Even here differences have not
been definitely established.
The origin (plate 1,B) from the gluteal
fascia, tail fascia, and caudal vertebrae
is not unusual, though in most forms
only caudal vertebrae one and two are
involved (origin from the first three, or
only the first, is not uncommon).
Keith (1894) reported that a great sacrosciatic ligament, represented by a thickened underportion of the sheath of the
gluteus superficialis, occurs in Cynopithecus (the Celebes ape) and is very strong
in Macaca arctoides. Kleinschmidt (‘49)
found this structure in Cynopithecus, and
a weak one in the Gibraltar macaque.
Patterson (‘42) stated that the gluteus
superficialis of the Celebes ape arises
from the ischial tuberosity. Other authors
who have written on macaques report
neither a tuberal origin nor a sacro-tuberous ligament.
Lachman (‘38) reports finding an origin
from the ischial tuberosity in the hamad-
322
JACK T. STERN, JR
ryas baboon, but almost certainly he has
mistaken a portion of the flexor cruris
lateralis for gluteus superficialis. No
other author who has described baboons,
including hamadryas, mentions a tuberal
origin. On the other hand, Schumacher
and Lebzelter (‘24) observed that the caudal fibers of the gluteus superficialis of
the mandrill arise from a sacro-tuberous
ligament (though not from the tuberosity
itself). Cuvier and Laurillard (1849, pl.
40) indicate no such origin, Bischoff
(1870) does not mention it, and I also
found no sacro-tuberous ligament nor any
special origin of the posterior portion of
the muscle in the mandrill. Furthermore,
neither the ligament nor unusual origin
occurs in the drill (Kleinschmidt, ’49;
Pagenstecher, 1867). Zielinska (‘36, ’37)
pictured the gluteus superficialis of Theropithecus as arising from a sacro-tuberous
ligament, but it is not reported by Appleton (‘27) and I found no hint of such a
structure (plate 1,B).
In Sernnopithecus ( = Presbytis) entellus,
Ayer (’48) observed that fibers of the
gluteus superficialis arise from a n “intermuscular septum” between the sacrum
and ischial tuberosity. Kohlbrugge (1897)
does not discuss this i n his description of
Sernnopithecus, Polak (’08) did not report such a n origin in Colobus, and Patterson (‘42) makes no mention of it i n
Rhinopithecus.
Until further evidence is gathered, one
is probably safe in assuming that neither
a sacro-tuberous ligament nor a n origin
of the gluteus superficialis from the ischial tuberosity occurs in any Old World
monkey with the possible exception of
Cynopithecus .
The insertion of the gluteus superficialis in Old World monkeys is entirely unlike that in any other primates. The
anterior fibers insert wholly onto the superficial surface of the deep lamina of
the fascia femoris (plates 1,B, 2,C). The
posterior fibers may do the same, but
more usually the deeper of these have a
weakly tendinous andlor muscular attachment to the posterior surface of the femur. The location of the femoral attachment is variable, but usually lies somewhere above the midpoint, and often quite
proximally. There is no formation of a
true lateral intermuscular septum.
The literature is unanimous in emphasizing the relatively small size of the cercopithecoid gluteus superficialis. Haughton (1865) found that it weighs less than
half the me&us. Nonetheless, the posterior portion is markedly thicker than the
anterior part of the muscle (plate 3,D).
Hylobatidae
The thin anterior portion of the gluteus superficialis arises from the gluteal
fascia and from an aponeurotic fascia
connecting to the lateral crest and spines
of the sacrum. This latter fascia is clearly
the homologue of the fascia which covers
the tail muscles in forms that have
them. The posterior portion of the gluteus
superficialis arises from the lateral edge
of the post-articular sacrum and from
caudal vertebra one (van den Broek, ’14;
Ranke, 1897). I did not note the exact
extent of the caudal origin in my specimens, but the muscle did not reach
the posterior region of the coccyx. Also
attaching to the first caudal vertebra
is a tubero-caudal ligament. On crosssection the ligament is “J” shaped, the
bend being located along the dorso-caudal
edge and the long arm lying deeply. The
gluteus superficialis arises from the superficial surface of the long arm and from
the concavity of the bend. The origin is
carried by the ligament to the ischial
tuberosity. A substantial portion of the
gluteus superficialis arises from the tuberosity and from the tendon of the long
head of biceps femoris.
In the siamang, the tubero-caudal ligament attaches also to the caudo-lateral
angle of the sacrum and to the posterior
inferior iliac spine. Near the ilium, the
ligament gives origin to fibers of the gluteus medius. Further medially, the gluteus
superficialis covers the most cranial region of the ligament, but few, if any,
muscular fibers arise from that spot.
Keith (cited in Uhlmann, ’68) found
that i n Hylobates muscular fibers arise
directly from the posterior superior spine
of the ilium, but this is denied by Kohlbrugge (1890) and Kanagasuntheram
(‘52). My observations also do not support Keith’s findings. Kohlbrugge (1890)
reported that in the siamang there occurs
a n iliac origin from the elevated ridge
SPECIALIZATIONS OF H U M A N GLUTEUS MAXIMUS
which medially borders the origin of the
gluteus medius. I found no trace of such
an origin.
Kanagasuntheram (’52) and Uhlmann
(‘68) claimed that the anterior portion of
the gluteus superficialis inserts into the
fascia femoris in Hylobates, but Kohlbrugge (1880) stated that this part of the
muscle inserts by means of a strong tendon into the femur just distal to the
greater trochanter (thus as in the “primitive” condition). My observations lend
support to Kohlbrugge, but I did find
that a few of the most cranial fibers of
the gluteus superficialis do attach deeply
to the fascia femoris on the lateral side
of the thigh. The tensor fasciae femoris
and gluteus superficialis are so thoroughly fused in the siamang that 1 could not
determine whether the gluteus has a partial fascia1 insertion, or the tensor has a
partial attachment to the ascending tendon, or they each have independent insertions into the tendon and fascia respectively. In my specimen of the gibbon, the
ascending tendon inserted from 9% to
15% down the femur. The corresponding
figures for the two siamangs are 11% to
23% and 17% to 3 4 % .
The posterior portion of the gluteus
superficialis inserts into the ascending
tendon and distally into the femur directly and by means of a tendon which is
fused to the aponeurosis of origin of the
vastus lateralis. Again, this represents
a true lateral intermuscular septum. It is
usually reported that the posterior portion
inserts as far as one-half to two-thirds the
way down the femur. In my specimen of
gibbon the muscular fibers continued just
beyond the femoral midpoint, but the tendon of insertion could be traced (with
some uncertainty) as far as the lower onefifth. In S y m p h a l a n g u s , the muscular fibers
end at a point roughly 60% down the
thigh.
The gluteus superficialis of the gibbon
weighs less than half the weight of the
gluteus medius (Tappen, ’55).
Pongidae
The general form and relations of the
gluteus superficialis of African apes (plate
1,D) is very similar to that in the Hylobatidae. The orang-utan presents quite a
323
different picture. A similarity between
gibbon and siamang on the one hand,
and the chimp and gorilla on the other is
somewhat mysterious; presumably it is
not based on a particularly close phylogenetic relationship, nor is the use of
the hindlimbs in the extant forms so alike
as to lead to convergent morphological
specialization. Possibly during some previous time the locomotor behaviors of
these‘ animals were more alike than is
now the case.
My observations on Pan and Gorilla revealed the great resemblance between
these forms in the structure of the gluteus superficialis and showed this structure to be almost identical to that described by Preuschoft (‘61) for the gorilla.
The origin from the gluteal fascia is extensive in the gorilla, and although I
found it less so in Pan (plate l,D), many
authors report otherwise. There is probably considerable variation in the regard.
Posterior to the origin from the gluteal
fascia, the muscle arises from the caudal
end of the long dorsal sacro-iliac ligament, which runs from the posterior superior iliac spine to the lower spines of
the sacrum. Many authors report a direct
origin from the sacrum, but I found that
such an origin was from the fascia which
covers the multifidus. A direct origin from
the ilium is claimed by some (Beddard,
1895; Bischoff, 1880; Miller, ’52), but is
not reported by the vast majority of authors, and I observed no such attachment.
The origin passes backward onto the
coccyx and sacro-tuberous ligament (plate
1,D). This ligament does not have the
configuration described above for Hylobates. In my specimens of African apes,
the sacro-tuberous ligament was a twisted
structure. Ligamentous fibers from the
medial part of the ischial tuberosity ran
deeply upward and forward to attach to
the caudo-lateral angle of the sacrum.
Fibers from the lateral region of the ischial tuberosity cross this group superficially
and attach to the coccyx near its tip.
These superficial fibers are much better
developed than the deeper ones. The gluteus superficialis reaches the ischial tuberosity by passing along the superficial
fibers. There is an extensive origin of
the muscle from the ischial tuberosity
and the tendon of the long head of biceps
324
JACK T. STERN, JR.
femoris. A separate ligament runs from
the caudo-lateral angle of the sacrum
upward to the posterior inferior spine of
the ilium, but the sarco-tuberous ligament has no direct connection to the ilium.
In the chimp and gorilla, the gluteus
superficialis inserts into the femur by
means of a well developed ascending tendon and a tendon fused with the aponeurosis of origin of the vastus lateralis.
In fact it was dissection of these primates
that led Champneys (1871), Ranke (1897),
and Klaatsch (‘00) to determine the role
played by the tendon of insertion of the
posterior part of the gluteus superficialis
in the formation of the lateral intennuscular septum.
In my specimen of Pan, the ascending
tendon attached from 20% to 33% down
the femur. Preuschoft (‘61) reports that it
inserted at the end of the proximal third
of the shaft in one specimen of gorilla,
in another specimen at the femoral midpoint. The posterior portion of the muscle
extends its insertion far below the midpoint of the femur (plate 1,D). Many authors state that it reaches the lateral
condyle, but one cannot always determine
whether muscular fibers or tendon are
being discussed. It is probably fair to say
that the muscle fibers continue at least
two-thirds down the thigh, and often
beyond.
There are various reports, not representing the majority, of an insertion into
the fascia femoris. In one specimen of
gorilla, Preuschoft (‘61) noted that a few
of the most anterior fibers of the gluteus
superficialis did so insert. I found this
in both African apes. Neither Preuschoft
nor I observed any other mode of insertion
into the fascia femoris, and it is my conclusion that an insertion into the lateral
intermuscular septum has often been misinterpreted as being into the fascia femoris. Also, in the chimp and gorilla, the
superficial surface of the ascending tendon is not entirely covered by muscular
fibers (plate 1,D), and the fascia femoris
may be bound down to the exposed tendon
surface. This could account for some incorrect descriptions of a fascia1 insertion.
In African apes, the anterior portion
of the gluteus superficialis is far thinner
than the posterior portion. The entire
muscle weighs substantially less than the
gluteus medius in Pan (Macalister, 1873;
Fick, ’25; personal data), but in Gorilla
the two muscles are almost of equal weight
(Macalister, 1873 ; Preuschoft, ’61).
The gluteus superficialis of the orangutan (plate 1,C) arises from the gluteal
fascia, the fascia over the multifidus (posterior to the sacro-iliac joint), and the
coccyx. An origin from a well defined
sacro-tuberous ligament is not found.
Primrose (1898-1899) stated that the
muscle arises from “sacrosciatic” fascia,
and van den Broek (’14) described a fragile tubero-caudal ligament giving rise to
muscle fibers from its external surface.
Sonntag (‘24) also reported an origin from
a sacrosciatic ligament, but Mysberg (‘1 7)
noted that such a structure, though present, could not be outlined either at its
beginning or at its end, where it seemed
to lose itself in the perimysium of the
gluteus superficialis. Boyer (‘35) noted
that the tuberosity of the ischium was
connected to the gluteus superficialis by
an extension of the latter’s fascia. Opposed to all these authors are an equal
number who do not mention a sacrotuberous ligament and some (Fick, 1895a;
Michalis, ’03; Kleinschmidt, ’49) who
deny its presence. One of my specimens
was dissected while still fresh. In this
animal I found a very weak fibrous band
which fits the description given by Mysberg. I did not notice such a structure in
my fixed specimens, but it may have
been overlooked because of its extreme
tenuosity .
The insertion of the gluteus superficialis in Pongo is more similar to the
condition in Ateles than in any other primate. The whole muscle inserts into a
strong ascending tendon (fig. 2,D); in fact,
the only reason for believing that a posterior portion exists is that fibers arise
from the coccyx. The external surface of
the ascending tendon is exposed to the
fascia femoris and they adhere, but the
fascia may be heavily fat-laden here and
no insertion into it occurs. The site of
attachment of the tendon is variously
reported, but usually stated to lie somewhere between one-quarter and one-half
the way down the femur. In one of my
specimens, the femoral insertion occurred
between 17% and 25% down the bone,
SPECIALIZATIONS OF HUMAN GLUTEUS MAXIMUS
in another specimen the comparable figures are 19% and 2 9 % .
Due to the great reduction of its posterior portion, the gluteus superficialis appears of nearly uniform thickness on
cross-section (plate 2,D). A similar phenomenon occurs in Ateles (plate 3,B). In
the orang-utan, the muscle weighs considerably less than the gluteus medius
(Fick, 1895b; Langer, 1879).3
Man
Features of the origin, insertion, size,
and shape of the gluteus maximus are
totally unique to man, and it is just these
features which we are seeking to identify
and interpret.
Textbooks are nearly uniform with regard to the description of the origin of the
gluteus maximus. What differences occur
between them, and between them and
what follows, are of little significance.
There may be an origin from the gluteal fascia, as is frequent in non-human
primates, but this is not a constant feature. When it does occur, however, i t
may be extensive. There is a constant
origin from the dorsal region of the
ilium. This occurs by means of a deep tendon which attaches to the posterior gluteal
line (the tendon being responsible for the
line) and by means of a direct fleshy
attachment to the ilium behind this line.
Immediately inferior to the ilium, the
fibers arise from the dorsal surfaces of
(a) the sacro-tuberous ligament, which
attaches to the posterior spines of the
ilium; (b) the long posterior sacro-iliac
ligament; and medial to this, (c) the fascia covering the multifidus almost up
to the sacral spines. The origin passes
backward along the multifidus fascia and
sacro-tuberous ligament. Where the multifidus ends, its covering fascia fuses with
the periosteum of the lateral portion of
the sacrum, and the gluteus maximus
therefore arises from the sacrum. The
origin then continues onto the COCCYX
nearly to its tip. Fibers arise from the
entire superficial surface of the sacrotuberous ligament, however, the number
of such fibers is relatively small. Furthermore, since the attachment of the ligament to the coccyx does not extend as far
caudally as the origin of the gluteus max-
325
imus from the coccyx, the most inferior
fibers of the muscle have no origin from
the ligament. This condition is therefore
different from what occurs in hylobatids
and African apes, and somewhat similar
to what is found in Alouatta palliata (and
the orang-utan?).
The truly unique attribute of the origin of the gluteus maximus is its strong
and extensive attachment to the ilium.
Related to this is an origin from the
sacro-tuberous ligament as it attaches to
the posterior spines of the ilium. Only in
man and the siamang does the ligament
even reach the ilium, and the gluteus
superficialis of the siamang does not arise
from either structure in this region. A
third unique characteristic of man is the
extent of the origin from the fascia over
the multifidus. Although an origin from
homologous facial layers occurs in all primates, the direct origin from the fascia
medial to the long dorsal sacro-iliac ligament is strictly human.
Descriptions of the insertion of the gluteus maximus are at wide variance with
each other. Most frequently, detailed accounts are not given. A common statement is that the entire cranial half of the
muscle inserts into the fascia lata whereas only the superficial fibers of the caudal
half attach here, the deeper ones going
to the lateral intermuscular septum and
into a tendon which inserts into the femur.
However, many authors report that all of
the caudal fibers have a septa1 and femoral insertion, while still others state that
the deep fibers of the whole muscle have
this attachment. Some authors deny a
fascia1 insertion altogether.
I have taken particular care in observing the intricacies of the insertion of the
3 The orang-utan i s unique among apes in possessing
a muscle that runs from the ischial tuberosity to the
lower one-half to two-thirds of the femoral shaft and
aponeurosis of vastus lateralis (plate 1,C) but i s innervated by a direct branch from the sciatic nerve and also
by a branch of the nerve to the long head of biceps
femoris. The muscle may be considered a portion of the
biceps femoris, or may be given the name “ischiofemoralis.” The action of the ischiofemoralis must be similar to that of the posterior fibers of gluteus superficialis
in other apes. However, it is not known if the role
played by the ischiofemoralis in the locomotion of the
orang is like that played by the posterior fibers of the
gluteus superficialis in the movements of the other
apes. Also unknown is whether or not any of the apes
is descended from a monkey-like ancestor that possessed a long head of biceps which inserted into the
thigh, as occurs in cercopithecoids and many ceboids.
326
JACK T. STERN. JR.
gluteus maximus, and my findings differ
only in one important point from the detailed account given by Sappey (1876).
Since the validity of his observations is
not generally acknowledged, I am reproducing two of his figures (plate 4) and the
following passage from his text (pp. 377378):
Les faisceaux superieurs s’inserent a la
face profonde de petits tendons rubanes
et paralleles, d’autant plus longs qu’ils sont
elevees, lesquels contournent le grand trochanter en se condensant et en formant une
lame epaisse, de plus en plus etroite, pour
aller se fixer sur la partie terminale de la
branche externe de la ligne Bpre. Cette lame
tendineuse est logee dans un dkdoublement de l’aponevrose fernorale, dont le
feuillet interne passe sur la face profonde
en lui adherent de la maniere la plus intime, tandis que l’externe, beaucoup plus
epais et tres-adherent aussi, passe sur la
face opposee.
Les faisceaux inferieurs se rendent a u n
gros et court tendon aplati qui se continue
en haut avec la lame preckdente, et en dehors avec l’aponevrose de la portion externe
du triceps crural; ce tendon s’attache a
la branche externe de la ligne ipre et a la
partie superieure de cette ligne.4
Sappey describes a purely femoral and
septa1 insertion of the muscle, and it is
with this that I disagree. He stated that
the superior portion of the muscle inserts
into the deep surface of a small tendon
composed of many ribbons. In fact, this
“tendon” is a deep layer of the overlying
fascia, and the fibrous tissue into which
the gluteus maximus inserts is continued
into the fascia lata (plate l,E,F). Sappey’s observations can be reconciled with
mine when it is realized that only the
superjicial fibers of the superior half of
the gluteus maximus gain an appreciable attachment to the fascia lata, while
the deep fibers go to a typical ascending
tendon which in turn inserts on the femur (plate 2,E,F). As in the great apes,
the surface of the ascending tendon adheres to the overlying fascia lata, and
this cannot only lead one astray in the
direction of believing that the entire insertion is into the bone (as did Sappey),
but also in the opposite direction of thinking that the entire insertion is into fascia.
To avoid this, dissections of fetal material
are helpful, for here the ascending tendon
stands out in greater relief.
The caudal portion of the gluteus maximus inserts almost totally into the ascend-
ing tendon and lateral intermuscular septum. However, a very small number of
superficial fibers may gain attachment to
the overlying fascia. An examination of
the lateral intermuscular septum reveals
quite clearly that it is composed of three
layers. The most posterior layer contains
fibers which run upward and inward toward the femur. These represent a tendon
of origin of the short head of biceps
femoris. Such a tendon is seen as a separate entity in Pithecia. The middle layer
is composed of fibers running downward
toward the femur. These can be seen to
emanate from the gluteus maximus and
represent the tendon of its caudal portion. The anterior layer consists of fibers
running in the same direction as the
short head of biceps tendon. These give
origin to the vastus lateralis. Because of
the different fiber orientations within the
lateral intermuscular septum, the structure has a criss-cross appearance.
In six adult specimens, the average
area of attachment of the ascending tendon extended from 14% to 32% down
the femur. This is rather low, though not
uniquely so (cf. chimp, gorilla, and siamang). However, upon inspection it is
clear that the far distal extent of the
attachment of the ascending tendon in
man is due to the fact that the lower
fibers expand markedly near their termination (plate 2,F). The main body of the
tendon does not insert much further distally than one-fourth the way down the
bone. The expansion results in the distal
tendinous fibers of insertion running nearly parallel to the bone, and in this respect
is reminiscent of the insertion of the
semitendinosus or semimembranosus. In
the latter cases, such a condition has
4 The superior bundles insert on the deep surface of
small ribbon-like and parallel tendons (the more superior ones being progressively longer) which twist
around the greater trochanter, condense, and form a
thick lamina that becomes narrower and narrower to
insert on the terminal part of the external bifurcation
of the linea aspera. This tendinous lamina is lodged in
a doubling of the femoral fascia, the internal layer of
which passes on the tendon’s deep surface, adhering to
it most closely, whereas the external layer, much
thicker and also closely adherent, passes on the tendon’s outer surface.
The inferior bundles go to a thick and short flat
tendon which is continuous superiorly with the lamina
discussed above and laterally with the aponeurosis of
the vastus lateralis. This tendon attaches to the external bifurcation of the linea aspera and to the superior part of the linea aspera itself.
SPECIALIZATIONS OF HUMAN GLUTCUS MAXIMUS
been interpreted (Mollier, '37) as being
a correlate of the nearly parallel pull
exerted on the tibia by these muscles
when the leg is extended. Possibly the
expansion of the ascending tendon of the
gluteus maximus indicates a pull on the
femur nearly parallel to its shaft.
The muscular fibers of the caudal portion of the gluteus maximus insert, on
the average, as far as 33% down the
thigh. Such a limited distal extent is
found also in prehensile-tailed cebids.
Even though the muscular fibers reach
little or no further down the thigh than
does the ascending tendon, the caudal
fibers of the muscle are able to gain
broad attachment to the lateral intermuscular septum because they insert lateral
to the expansion of the ascending tendon (plate 2,F).
The unique characteristics of the insertion of the gluteus maximus are (a)
the extensive attachment of the superficial fibers of the cranial portion into
the deep surface of the overlying fascia,
and (b) the broad expansion of the lower
fibers of the ascending tendon. All other
aspects of the insertion in man can be
duplicated i n the lower primates, though
the limited distal extent of the insertion
of the cqudal fibers is uncommon.
The gluteus maximus weighs more than
twice the medius (Voss, '56; Schumacher
and Wolff, '66). This is unparalleled in
other primates. But it is not sufficient to
state this fact without inquiring wherein
the extra bulk of muscle is concentrated.
Ranke (1897) noted that in lower primates the superficial gluteus comes predominantly from the tail vertebrae, whereas in man only the slightest portion of
the fibers arise from the coccyx. He emphasized the great mass of the part arising from the sacrum. Cross-sections of
the bellies of the gluteus superficialis
and maximus (plate 3 ) provide us with a
good indication of where the additional
fibers in man are located. It can be seen
that the anterior portion of the muscle
is equal to or greater in thickness than
the posterior portion in man, but is thinner, most often markedly so, than the
posterior portion i n all other primates.
The large size of the cranial portion of
the gluteus maximus correlates well with
the new firm origin from the ilium, the
327
more extensive origin from the multifidus
fascia medial to the long dorsal sacroiliac ligament, and the origin from the
sacro-tuberous ligament near the iliac
spines. Whether or not the relatively large
weight of the gluteus maximus is entirely attributable to the increased cranial
portion has not been determined.
DISCUSSION
The evidence accumulated above demonstrates quite clearly that the unique
morphological specializations of the human gluteus maximus are confined to
its cranial portion. This part of the muscle is much thicker than in any other
primate. It has a new and firm origin,
a modified ascending tendon of insertion,
and a n entirely new insertion into the
overlying fascia continuous distally with
the fascia lata. Of interest now, is the
identification of those functional abilities
which are made possible by the unique
anatomical configuration. Having done
this, we can consider a possible selective
pressure favoring such abilities and look
for evidence in fossil man of the changes
which were occurring.
The cranial portion of the gluteus maximus is certainly not that segment which
is topographically best suited to produce
extension of the thigh. On the contrary,
the caudal fibers of the muscle have the
most favorable moment arm for extension,
yet they exhibit no peculiarity which cannot also be seen i n other primates. Of
course, these fibers have been adjusted
so that their physiological resting length
occurs when the leg is in line with the
trunk, as opposed to what can be presumed to be the case in quadrupedal
forms in which the resting length is likely
to occur when the femur is positioned at
about 90" to the trunk in a sagittal
plane. Furthermore, the angulation of
the human sacrum (probably a n obstetrical necessity) grants to the caudal portion
of the gluteus maximus a leverage which
would have been markedly reduced had
not the position of the sacrum been
changed from that seen in non-human
primates. These two modifications, one
physiological, the other morphological, enable the gluteus maximus to extend the
lower limb beyond the resting position
328
JACK T. STERN, JR.
with power. However, it can certainly be
assumed that in most other primates the
gluteus superficialis can extend the lower
limb beyond the resting position with
power. Thus, the changes in m a n have
been directed to the preservation of a n
old ability, rather than to the creation of
a new one.
That the extensor activity of the gluteus maximus is primarily important as
a n aid to the hamstrings during activities
which require special effort has been
demonstrated by Wheatley and Jahnke
(‘51), Joseph and Williams (’57), Karlsson
and Jonsson (‘65), and Pauly and Scheving (‘68). It has no specific role as a n
extensor in erect posture or locomotion.
Duchenne (1867) observed that paralysis
of the gluteus maximus does not impair
standing or walking. Subsequently, it has
been shown (Joseph and Williams, ’57;
Karlsson and Jonsson, ’65) that the muscle is not electrically active in standing
at ease. If, during standing, the center
of gravity of the trunk is shifted forward,
the hamstrings are the first to be called
into action, and most often they alone
suffice to maintain equilibrium. The great
importance of the hamstrings in erect
posture is suggested by the nature of the
changes in the ischial tuberosity which
have occurred in human evolution.
The gluteus maximus is active during
walking (Eberhart, Inman and Bresler,
’54; Battye and Joseph, ’66), but not in
all subjects (Sutherland, Bost and Schottstaedt, ’60). When it is active, it functions a t the beginning of the stance phase,
presumably to assist the hamstrings in
preventing jacknife of the trunk (as Cuvier suggested).
Most of the electromyographic studies
of the gluteus maximus have involved
recording from the “middle” of the muscle. However, because of the very special
nature of the cranial portion, i t is essential to learn whether this behaves differently from the remainder. Jonsson and
Steen (’63) and Karlsson and Jonsson
(‘65) provide the essential information.
Although both parts are equally active
during extension of the thigh or trunk,
a difference occurs during abduction. Previous authors have speculated on a role
of the cranial portion of the gluteus maximus i n abduction; some believed it was
possible, others denied it. The recent electromyographic evidence indicates quite
clearly that the gluteus maximus, p i n cipnlly its csnninl past, is often called into
action during forceful abduction of the
thigh and during support on one leg.
That the portion of the muscle most modified morphologically should be the portion active in forceful abduction leads me
to suggest that the evolutionary history
of the gluteus maximus was directed toward improving the all important ability
to control lateral stability of the trunk.
All the changes which characterize the
anterior portion are such as to improve
its strength and leverage for abduction.
The abducting role of the gluteus maximus in locomotion has not been studied,
and it certainly should be. However, several interesting clues can be gathered
from the literature. In walking on a level,
the period of activity of the gluteus maximus coincides with that of the gluteus
medius. The two muscles have been
thought to perform different functions
during this period, but the possibility that
they perform similar functions must exist.
It is also of note that the glutei maximus and medius contract simultaneously
during climbing and descending stairs
(Joseph and Watson, ’67). In bicycle pedalling, neither of these muscles are consistently active except when resistance to
movement is great (Houtz and Fischer,
’59). Then, both muscles act during the
same phase of the pedalling cycle. These
various facts do not represent strong evidence that the functions of the glutei
maximus and medius are often the same,
or even partly so, but investigation of this
possibility would seem worthwhile.
Although the gluteus maximus may
function partially as a n abductor in bipedal walking, the evidence leads us to
believe that such action is not essential
for this mode of locomotion. I would like
to speculate that the abductor function
of the gluteus maximus may be more important in modes of locomotion in which
the unsupported weight of the body falls
onto one limb from some height. Running
is such a mode of locomotion. Slow running, or jogging, would seem particularly
noteworthy, since at low speeds the vertical oscillations of the center of gravity
are greater than at high speeds. Also,
SPECIALIZATIONS OF HUMAN GLUTEUS MAXIMUS
329
in running, the trunk is somewhat flexed speculations offered above are correct, the
on the femur and the cranial fibers of the Makapansgat inhabitants were venturing
gluteus maximus would be in a more fa- into the role of long distance predators.
vorable position for abduction.
Recently the major portion of a left inThe speculation can be carried further: nominate (Olduvai hominid 28) attribis jogging such an important mode of loco- utable to Homo erectus has been described
motion that the evolution of the gluteus by Day ('71). It is stated that a posterior
maximus could be in response to its gluteal line is present. However, the pubdemands? An answer might be provided lished photographs of this specimen indiby considering primitive hunting beha- cate some damage to the outer surface
vior. Life studies of Bushmen (Garst, '69; of the ilium just antero-superior to the
and personal communication from R. Sing- posterior superior 'spine. This is the region
er) indicate that jogging is the mode of that in modern man shows the clearest
locomotion used to track wounded prey indication of the posterior gluteal line
for many miles. May not the necessity and enables one to estimate the size of
for the protracted hunt have placed selec- the area devoted to the origin of the glutive value on changes in the gluteus teus maximus. We will probably need to
maximus which would enable it better await the discovery of a well-preserved
to participate in controlling lateral sta- ilium of Home erectus before we can find
bility of the trunk? If so, then the develop- evidence that nature has completed those
ment of the posterior gluteal line of the very inportant changes in the anterior
ilium and the expanded portion of the portion of the superficial gluteus which
iliac blade behind this line may be im- are the hallmark of mankind.
portant osteological evidence of well established hunting behavior.
ACKNOWLEDGMENTS
Dart ('49) stated that a posterior gluteal
I wish to thank Drs. Ronald Singer,
line could be traced with tolerable accuracy on the left ilium from Makapans- Charles Oxnard, and Mr. Timothy Strickgat. He noted that the posterior gluteal ler for reading this manuscript and proline passed much closer to the posterior viding thoughtful comments and critiiliac spines in Australopithecus prometh- cisms, I also wish to thank the Field
eus ( = africanus) than in modern man, Museum of Natural History (Dr. Karl
and, therefore, that the area of origin Liem, Curator of Vertebrate Anatomy) for
for the gluteus maximus was much small- providing numerous valuable specimens
er in the fossil. My examination of the for dissection. This work was supported
Wenner-Gren Foundation cast (F-ST6) of by General Research Support grant PHSthe right innominate from A. ufricanus at RR-05367 and by National Sciepce FounSterkfontein disclosed nothing which re- dation grant GB-29296.
sembles a posterior gluteal line. UnforLITERATURE CITED
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PLATE 1
EXPLANATION OF F I G U R E
1
332
Lateral view of the right hip and thigh demonstrating the general configuration of the gluteus superficialis (GS) or gluteus maximus (GM).
BLH, long head of biceps femoris; BSH, short head of biceps femoris;
FCL, flexor cruris lateralis; STL, sacro-tuberous ligament; TFF, tensor
fasciae femoris. A - Galago senegalensis; B - Theropithectis gelada;
C - Pongo pygmaeiis; D - P a n troglodytes; E - H o m o snpiens fetus;
F - H o m o sapiems, adult. The “primitive” condition is demonstrated
in Gnlngo. Note that in Old World monkey ( B ) almost the entire
muscle inserts into the fascia of the thigh. In the orang-utan, the entire
muscle inserts tendinously into the proximal region of the femur. The
origin of the gluteus superfacialis in the chimpanzee differs from the
“primitive” state in that the muslce arises largely from the sacrotuberous ligament and ischial tuberosity. Note that i n man the anterior fibers of the gluteus maximus insert into the overlying fascia and
that the posterior fibers do not extend far down the thigh.
SPECIALIZATIONS OF H U M A N GLUTEUS MAXIMUS
Jack T. Stern, Jr.
PLATE I
PLATE 2
EXPLANATION
2
334
O F FIGURE
Lateral view of the right hip and thigh with gluteus superficialis (GS)
or gluteus maximus (GM) cut to show insertion of the anterior portion
via the ascending tendon (AT) in all forms except Old World monkeys.
GMp, posterior (inferior) portion of gluteus maximus; GSp, posterior
portion of gluteus superficialis; TFF, tensor fasciae femoris. A - Galago senegalensis; B - S a i m i r i sciureus; C - M a n d r i l l u s s p h i n x ; D Pongo p y g m a e u s ; E - H o m o s u p i e n s fetus; F - Homo s a p i e n s adult.
The “primitive” condition, characterized by a narrow ascending tendon inserting quite proximally on the femur and a large posterior
muscular portion inserting over the major portion of the femoral
shaft, is seen in Galago and Saimiri. Note the absence of an ascending
tendon i n the Old World monkey (C), and the distal expansion of this
structure in man. The insertion of the posterior portion of the gluteus
maximus into the aponeurosis of the vastus lateralis can be seen i n
the adult specimen of man.
SPECIALIZATIONS O F H U M A N G L U T E U S MAXIMUS
Jack T. Stern, Jr.
PLATE 2
PLATE 3
EXPLANATION
3
336
O F FIGURE
Lateral view of the right hip and thigh with bisected gluteus superficialis (GS) or gluteus maximus (GM) demonstrating the relative
thicknesses of the anterior and posterior portions of the muscle.
AT, ascending tendon; GSp, posterior portion of gluteus superficialis. A - Propithecus uerrauxi; B - Ateles geoffroyi; C - Alounttu
cnraya; D - Cercopithecus aethiops; E - Homo sapiens fetus; F H o mo sapiens adult. Note that the anterior portion of the muscle
is thicker, usually markedly so, than the posterior portion in all primates except man.
SPECIALIZATIONS OF HUMAN G L U T E U S MAXIMUS
J a c k T. Stern, Jr.
PLATE 3
PLATE 4
EXPLANATION OF FIGURE
4
Reproduction of figures 315 (left) a n d 316 (right) from Sappey (1876).
The gluteal region of m a n is depicted. Sappey employs the following
labels: Figure 315-1
= gluteus maximus; 2 = inferior portion of
gluteus maximus; 3 = tendinous bundles by which the inferior portion attaches to the whole extent of the external bifurcation of linea
aspera; 4 = superior part of gluteus maximus; 5 = tendinous rihbons by which superior part also goes to insert on external bifurcation of linea aspera; 6 = superior part of the femoral aponeurosis;
7 = doubling of this aponeurosis at the level of the superior border of
the gluteus maximus; 8 = portion of its superficial lamina that adheres tightly to the tendon ribbons; 9 = inferior extremity of tensor
fasciae latae; 10 = portion of the femoral aponeurosis continuous
with the tendinous bundles of the tensor, excised i n order to show
insertion of gluteus maximus to femur. Figure 316 - 1 = gluteus maximus; 2 = insertion of gluteus maximus to external bifurcation of
linea aspera; 3 = triangular aponeurosis formed by converging tendinous bundles of the superior part of gluteus maximus.
SPECIALIZATIONS OF HUMAN GLUTEUS MAXIMUS
Jack T. Stern, Jr.
PLATE 4
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