advantage bipedalism & food transport

7/27/2019 Advantage Bipedalism & Food Transport

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Food Trunspmt und the origin of Hominid BipedalismGORDON W. HEWES

University of ColoradoANS upright posture and bipedal gait have been justly considered out-M standing features of human nature, for example by Haeckel (1868),Darwin (1871), Engels (1876), Munro (1893), Smith (1913), Hootan (1925),Jones (1926), Freud (1930), Weidenreich (1946, 1947), Keith (1949), Schultz

(1950, 1951), Washburn (1951, 1959), Mayr (1951), LaBarre (1954), W. E. L.Clark (1955, 1959), Piveteau (1957), Delmas 1958), Vallois (1958), Howells(1959), and Dart (1959a). For Engels in 1876, erect posture was the decisivestep in the transition from ape to man, an idea he shared with Haeckel( l868,1906 ed.:405) who said that upright posture was the first of the three greatprocesses in the development of the human organism. For Hooton (1925),man became man when he definitely took to the ground and assumed uprightposture and bipedal progression. Freud (1930: 66n) wrote t hat Mans erectposture would represent the beginning of the momentous process of cul-tural evolution. Schultz (1951:38) asserted tha t the acquisition of uprightposture was the first major step in mans evolution. Mednick, studying theevolution of the human ilium (1955), states that the evolution of bipedal loco-motion seems to have preceded other uniquely human attributes. It appearsquite probable tha t our ancestors walked first, and subsequently became large-brained, tool-using humans. W.E.L. Clark (1955:13-14) believes that bi-pedalism was the mosi important single factor in Hominid evolution. Piveteau(1957:278) cites the adoption of upright posture as the decisive dispositionfor the individualization of the human branch, with Pongid and Hominiddivergences having their point of departure chiefly in modifications of the pel-vis (p. 307). Washburn, who has dealt in detail with the locomotor changeswhich apparently initiated hominization, considers bipedalism the basic adap-tation for the foundation of the human radiation (1951:68-70), starting manon his separate evolutionary path (1959:31), though tool-using may havebeen almost as early (1960a) or simultaneous (Washburn and Howell 1960:35-37, 47). DuBrul (1958:90) notes that upright posture is essentially a reduc-tion of the repetition of structures serving the same function, with the fore-limbs becoming as it were, accessory mandibles rather than locomotor de-vices, leading t o a new mode of feeding and feeding niche. Mayr (1951) saysthat upright posture led the protohominids into a completely different adap-tive zone where new and severely increased selective pressures developed.

If these ideas are valid, it is extremely important to show not only whatchanges occurred in the pelvis and limbs of the evolving protohominids, butwhy they occurred-i.e., to determine what conditions would make such an

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688 Americaia Anthropologist [63, 1961anatomical transformation biologically advantageous. This paper is an effortto set forth a reasonable and sufficient explanation which has the further meritof being experimentally testable, within limits, using infrahuman Primate sub-jects.

Bipedalism is of course not limited to man (cf. Reynolds 1931). Birds arebipeds, and penguins stand in a fully vertical posture. Many Mesozoic reptileswere bipedal. Certain marsupials and rodents are bipedal and, among the carni-vores, bears are well known for their occasional upright stance and locomotion,which happens to be quite manlike. Valuable comparative work has been doneon non-Primate bipedalism (cf. DuBrul 1950), but none of these studies indi-cates why regular bipedalism came about in the ancestry of mankind.The bipedal proclivities of many infrahuman Primates are well known.Such behavior is spontaneous and not dependent upon human training or ex-ample (Riesen and Kinder 1952; Weidenreich 1947: 223; Schultz 1950, 1951: 3;Keith 1912; Darwin 1871; Haeckel 1900; Smith 1913). Even lemurs are occa-sionally bipedal, notably sifakas and indris. The highly arboreal New Worldmonkeys are rarely bipedal, though the capuchin is readily trained to this gait.Among Old World monkeys, bipedalism is spontaneous though infrequent inmacaques. A juvenile stumptail macaque being studied at the University ofColorado walks and stands upright with ease and without training. The stanceand gait are bent-kneed (cf. Washburn 1951:71, who goes into valuable detailon muscular changes involved in the assumption of fully human bipedalism).Among the great apes, bipedal proficiency varies from the rare upright stancein orangs to the easy biped walk or run of gibbons, but also on an individualbasis. Dart (1959a:218) quotes a case of a Munich zoo orang who learned twalk and stand upright, with the soles of his feet flat rather than curled inwardlike the ordinary members of his species. Kohler noted that some of his chim-panzees, whose peculiar build is well adapted to the upright posture, wouldadopt bipedalism as a fashion or form of play for several days at a time(1959:279). I have observed easy bipedal walking in one of the subadultgorillas at the Cheyenne Mountain Zoo in Colorado Springs. A newly cap-tured male gorilla living under semi-natural conditions in the former BelgianCongo has been photographed striding bipedally with a large bundle ofleaves under one arm Li je magazine 1960), and also running upright whilebeating his chest in the manner first described by Du Chaillu. Schultz (1951:38) concludes that the ability to walk bipedally is unmistakably present inapes, but perfected only in man. Whatever the reasons for this behavioralalternative to quadrupedalism among the infrahuman Primates may be, wemay consider this ability to walk bipedally as a given, antecedent to the evolu-tionary emergence of the Hominidae. I t is essential to our argument thatmany, if not most, Primates can walk bipedally if need be, bu t also essential t oremember that no nonhuman Primate regularly and habitually uses bipedal lo-comotion. This is what has to be explained, and not the given anatomicalcapacity to walk or stand upright occasionally.Our intention is not to examine the many interesting side-effects of bipedal-


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HEWE:S] Origin of Hominid Bipedal ism 689ity and vertical posture on human anatomy and physiology, some of whichhave left scars well known to the medical profession (Hooton 1946; Keith1912; Krogman 1951; Martin and Saller 1958: 1006; DuBrul 1958:38). Thepersistence of inguinal hernia, intervertebral disc difficulties, various circula-tory defects, etc., suggest tha t Schultz (1951:58) was optimistic in stating thatbipedalism had been perfected in man. More to the point of this paper, thesedefective adaptations suggest that natural selection for bipedalism among theemergent hominids must have been rapid and ruthless.Thanks to recent work on fossil Australopithecinae, we are sure that theachievement of upright posture and gait came well before the expansion of thebraincase and reduction of the snout to human proportions (W.E.L. Clark1954a; Howell 1955; Spuhler 1959; Washburn 1959; Etkin 1954: 132; Piveteau1957:315; Dart 1958b, 1959a). Only a few decades ago, the prime mover ofhominization was seen to be the expanding cerebral cortex (Smith 1913; Teil-hard de Chardin 1958: 157). As late as 1948, Kroeber could at tr ibute the evolu-tion of mans capacity for culture almost exclusively to cortical change (pp.68-71). T o be sure, culture in its later manifestations would have been impos-sible without an enlarged brain, but such a brain now seems to have been onlyone of the responses to new living conditions made possible by the shift to regu-lar bipedal locomotion (Shapiro 1956: 19). Indeed, Piveteau (1957: 65) men-tions a mechanistic hypothesis for the expansion of the prehominid brain, as adirect consequence of i e attainment of the erect posture. With the head bal-anced on top of the spine, the heavy neck muscles would be reduced; this inturn would permit the occipital expansion of the skull, accompanied bylessened muscular involvement of the temporals arising from reduced jaw andtooth size. Piveteau notes that this theory reverses the relation of brain tobraincase, and ignores the fossil evidence of rather heavy neck musculature inNeanderthal man with his large braincase.Stated simply, our problem is: why did certain quadrupedal Primates, al-ready capable like other Primates of sporadic bipedalism, become habitual bi-peds? (Cf. Vallois 1955:2176-77; Washburn and Howell 1960:47.) Our sug-gested answer, to be elaborated below, is: because the effective use of a newfood resource required its transport over considerable distances, and only bi-pedal locomotion, by freein g the arm s and h ands for carrying, could achievemaximal transportational efficiency. Obviously we are dealing with a time be-fore the invention of pack-straps and pack-saddles-cultural solutions to ani-mal transport which permit even hoofed quadrupeds to carry heavy loads forlong distances.Mendes-Corr&a 1924) once divided theories of anthropogenesis into thosestressing external (exogenic) conditions, such as changes of habi ta t or food,and those emphasizing internal (endogenic) conditions, such as changes in thebrain, sexual, and social behavior. Theories accounting for hominid bipedalismcan be similarly divided. Thus, Elliot Smith laid great emphasis on the brain,vision, and hand and eye coordination, with erect posture a by-product of thegrowing importance of hand-eye coordination as the hand is freed k o m loco-


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690 American Anthropologist [63, 1961motor tasks (1913). Kroeber (1948: 68) said th a t with capable-enough bra ins,chimpanzees could have achieved culture without ever becoming bipeds.Ha yes and Ha yes (1954) agreed with th is on the basis of thei r chimpanzee re-search, claiming th a t erec t posture was a secondary ch ara cte r of only mod er-at e impo rtance. St ra us (1953) dissents most vigorously. On this plan et, a tleast, brains capab le of carrying on culture have only developed in bipeds.Science fiction pres en ts numero us an d ingenious examples of culture-c arryingorganisms of non verteb rate s truc ture , an d we must not insist t ha t for the uni-verse as a w hole, cult ur e is limited to b ipeds (cf. Howells 1959:344-45).T he complexity of the anatom ical ad justm ents required for easy bipedallocomotion (cf. Delmas 1958) makes i t unlikely t h at hominid bipedalism cam esuddenly as the result of a few convenient m uta tion s, or by genetic drif t in atiny , isolated population (K eith 1949: 169). No r does it help mu ch t o spe ak oftren ds (Hill 1950) without accounting for the m , and without showing how evena slight change might be biologically useful t the outsel. Simpson has dealtharshly with all such nonexplanatory suggestions (1951) and goes on t o cite th edeve lopm ent of h um an upright pos ture as a good case of specializa tion whichbroadened rather t ha n restricted the ad aptive type .W ashburn (1951: 71-72) once advanced a n endogenic hypothesis for t hebackward bending of t he hominid ilium and t he change in the fun ctio n ofgluteus maximus as responses to the need to keep th e bony birth canal in suit-able relation to feta l head-size. Recen tly (1960b: 73-74) he has se t th e time forthis obstetrical crisis after the assump tion of hab itua l bipedalism an d suggeststh at i t was solved by th e delivery of the hu m an infant a t a relatively earlierst ag e of fetal development.Grad ual acquisition of bipedal facility need no t have been a t the expense ofearlier useful motor habits, at least not for a very long time. W.E.L. Clark(1954b: 71-72; 1955: 153) notes th at the Australopithecus ta lus indicates reten -tion of a more flexible an d mobile foot th an mo dern ma ns; pe rh ap s for his sizeand weight, Australopithecus was still an expert climber. But even modernhum ans, when suita bly trained from childhood, remain excellent climbers, an dif in good cond ition, certainly exceed gorillas in acro batic ab ilit y. No r hav e allof us utte rly lost our ab ility to ru n on all fours (Fig. l c ; cf. HrdliEka 1931).D ar t (1959a) calls atten tion to the expertise of the B ushmen im itatio ns ofquadrupedal animal gaits in games an d dances. I n dealing with a cre atu re suchas man, we mu st not overlook the probability th at all cultura l systems hav e acertain vested interest in making the distinctions between man and other ani-mals as sha rp as possible (D ar t 1959a: 223; Pa trid es 1958). H um an ity is self-consciously bipedal.T he long-argued issue of brachiation or nonbrachiation as a stag e in mansevolution is not crucial here (Gregory 1928a, 1928b). Our ancestors obviouslyavoided the seeming dead-end represented by the long-armed apes. TheHom inidae might hav e arisen from a generalized terrestrial prono grade ap e,or from a quasi-pongid brachiato r lacking th e extreme specializations of th emodern anthropoid apes. Th e fact th at hu ma ns use their hand s quite natu rally


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HEWES] Origin of Hominid Bipedalism 69

Wll

a

WXFIG.1 Primate bipedalism and quadrupedalisin from photographs).

a Young stumptail macque walking bipedally, carrying grapefruit.b. Young stumptail macaque tanding bipedally, eating grapefruit.c. Adult human 0 walking quadrupedally, showing spontaneous plantigrade use of hands.


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692 American Anthropologist [63, 1961in plantigrade fashion when walking or running on all fours is probably quitesignificant, as several authorities have noted (Fig. lc). The question of the pre-cise geological placement of the separation of the hominids from the main an-cestral stock (including the ancestry of the modern Pongids) is not crucial toour argument either (Straus 1953:89), though it might become relevant insome future assessment of fossil prehominid and paleoecological evidence(Simons 1960).For Hooton, increased body size brought mans ancestors out of the trees,as it seems to have for the gorillas (1946: 134-135). Since they were far moreintelligent than present-day apes, our ancestors quickly made the supremelyintelligent choice of becoming bipedal, which not only increased their visualrange by elevating their heads, but emancipated their hands for weapon-wielding, tool-using, and food-gathering (p. 138). This rationalistic interpreta-tion is quite implausible and, with respect to accounting for increased bodysize, about as convincing as an attempt to explain the size and habits of whalesby the fact that their ancestors grew too big to remain on land. Yet Hootondismissed with justifiable wit J. R. de la H. Maretts theory that human up-right posture was the end-product of skeletal responses to a diet overly rich incalcium. Another unlikely theory is that human bipedalism was a response tocold ground and snow-cover (not so absurd in the case of penguins, perhaps).Kohler remarked that his chimpanzees walked upright when the ground waswet and cold (1959:278-79). Coon (1959) agrees with me that the snow or wet-ground factor cannot have been important in the evolution of hominid bi-pedalism. Hardy (1960a,b,c) at tributes mans upright posture to water supportin the littoral aquatic environment which he most ingeniously credits for mansnumerous and peculiar deviations from the standard Primate pattern. Hardysrevolutionary thesis does have the merit of focusing attention on ecological de-terminants, rather than on inexplicable drives to master tools and weapons.The commonest explanation for the origin of human upright posture andgait relates these to tool and weapon using, and to offense and defense. Reyn-olds (1931:311) was almost alone in considering simple dodging, quite apartfrom tools or weapons, in defense or pursuit, as a crucial factor in the finalswitch-over to regular bipedalism. Bartholomew and Birdsell (1953) have givenus a remarkably vivid reconstruction of the ecology of the fossil protohominids,in which they stress the importance of bipedal locomotion. Even though ordi-nary Primate bipedalism is inefficient and infrequent, a significant non-loco-motor advantage must have accrued from even the partial freeing of armsand hands. Agreed. But they go on (p. 482) to say that this advantage lay in themanual use of adventitious tools and weapons, adding, only man has his loco-motion essentially unimpeded while carrying or using a tool (my italics). Tool-carrying is mentioned but not stressed as a factor in hominization by Wash-burn (1960:69), and by Hockett (1960:96). Etkin (1954: 136) discusses Pri-mate habits of carrying infants and the implications of infant transport on theefficiencyof a hunter anthropoid, but fails to mention food transport. These,a n d a general statement by Mason (1896:255-56) are almost the only ones


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HEWES] Origin of Hominid Bipedalism 693I have encou ntered in a fair sample of the l i terature deal ing with h um an evol-utio n which m ake specific m entio n of the possible im po rta nc e of c arry ing activ -i ty. My disagreement is only over the natu re of th e burdens carr ied by th eincipiently bipedal protohorninids an d the relation of this carrying t o th eem ergenc e of hab itua l bipeda lism.A long l ist of nam es can be cited for the notion t h a t freeing th e hand s fortool-using, weapon-handling, food-gathering, and self-defense was the maincause of hom inid bipedalism (Da rw in 1871; Haeckel 1900; Ca rte r 1953; Hill1954; Sha piro 1956; W ash bu rn 1959: 24; Oakley 1960:322). Cau se an d effectare blurred in many presentat ions. Some authors bel ieve that increasing de-mands on the h ands led them to be f reed from locomotor tasks; others seem toregard bipedal ism as a hap py accident which released the han ds for m anipula-tion. So viet theories of anthrop ogen esis stress the freeing of th e ha nd s as a re-sponse t o the need to m anipulate tools. K osven (1957: 15) writes, for exam ple:T his development of t he han ds in the process of t h e imp rovem ent of the en tirehu ma n organism followed the developm ent of th e up righ t posture. Neithe rEngels (1876-1950 ed.) long ago, nor Kosven men tions carrying, though Engelsvaguely spoke of oth er function s increasingly devolving on the hand s. W ash-bu rn (1960a), disagreeing with m y notion of food tran spo rt , adh eres to D ar-wins idea th at tool-using was the k ey to upr igh t posture. H e s tates , surelywith out po ssibility of disagreem ent, th a t use of a digging stick would easilydouble a baboons food-supply, and that stones suitable for food-grubbingwould also be advantageous, adding that such tools would have to be carriedalong, a n d th a t this would be nearly impossible in l iving mo nkey s an d apes. Ithink h e exaggerates the difficulty of tran spo rting a l ight st ick ; most ap es ormonkeys can ca rry a s t ick t r ipodal ly for fai r ly long dis tances witho ut fat igueor , in open coun try, cross-wise in the mo uth, just as do mest icated dogs can bereadily train ed to ca rry st icks.I do not quar re l wi th the idea th a t the hands have p layed a n imp or tant ro lein the evolut ion of man and cul ture , bu t I find i t v ery difficult t o believe t h a tthe use of tools or weapon s was of s uch im por tanc e in the prim ord ial stag es ofhominizat ion that i t e l ic i ted habi tual bipedal ism. My thesis is that the armsan d hand s were needed for som ething other than locomotion: the carrying offood, an d th a t only a bipedal gait could permit them to fulfi l l this need withreal efficiency. Bipedal locom otion can be elicited ins tanta neo usly in m aca que s(and probably most o ther infrah um an Primates) b y present ing a sufficientlybulky food burden a nd sub sequent ly threatening t o tak e i t aw ay. Bipedalismwill be maintained as long as the anim al is pursue d, provided he does no t f inda safe perch o r is not so terri fied by his pursuer th at he aban dons the food bur-den a nd rever ts to the more rapid quadrupedal ga i t . If the pursuer hal ts , theanimal may stan d erect , a t tem ptin g to s tuff th e food into his mo uth , bu t wari lypoised for furth er b ipedal evasion.

Spu hler refers to the freeing of the hand s for manipulat ion an d sensory in-spection, etc., as a qua ntum leap (G. G. Simpsons te rm ), possible up on theachiev eme nt of upright. posture (1959). Tw o w eighty co nsideration s force m e


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694 American Anthropologisl [63, 1961to reject this view. First, monkeys and apes are constantly busy with theirha nd s in nonlocomotor activity-grooming, grubb ing food, inspectin g, pickin g,peeling, and conveying it to their mo uths; the y also exhibit some rudime ntarytool-using (Kohler 1959). Hyperactive manual behavior has probably been acharac teristic of th e Pr im ate O rder since th e Eocene. Since these manip ulationsare biologically advan tag eou s, an d if freed h and s are positively correlatedwith upright posture an d bipedalism, th en mo st of the P rim ate s should behabitual bipeds by now, with the anatomical modifications associated withhuman bipedalism : broad, twisted ilia, shortened ischia, etc. Second, thesemanual activities do not in fact require upright standing or bipedal locomo-tion. Even in modern man, I would guess that 80 percent of all tool-using isaccomplished in sitting , squat ting , or kneeling positions (Hewes 1955; 1957),and in particular , when the tool-using has to do with cutting , pounding, scrap-ing, or split ting of food (outside of W estern an d a few other cultures). Ancienthominids probably very seldom stood up as they worked with their simpletools; the y certainly did not s tan d up t o work-benches. Tho ugh stand-u p tool-using exists, notably in agriculture and forestry, even the digging stick ismanipulable from a squatting position-and is so used among the Australianaborigines.

Weapons, on the contrary, often demand an upright stance for effectiveuse, unlike oth er kind s of tools. D arw in stre ssed th e defensive ad va nta ge s oferect posture when coupled with the use of stones or clubs, or in at ta ck , orotherwise to ob tain food. A man-sized animal could not deliver a very crush-ing blow while squ attin g or sittin g on the ground unless his victim were quitesmall. Jabbing with sticks or hurling stones would be most efficient from astandin g posture. W ithout weapons, a fighting hominid a t least sta rts to fightstandin g up. D ar t (1953) has graphically set forth the adva ntage s of a pivotingtrunk on a firmly balanced bipedally su pp orte d pelvis, for th e supposedly club-wielding Australopithecinae. I n a recent work (1959a: 195) he states th at clubsmu st have been decisive in ge tting protohominids u p on their hind legs. Da rtreasons that australopithecines, trekking across grasslands, though originallyquadrupedal, would develop hab its of stan din g up to to search for food or spotenemies (p. 196), unstable an d vulnerable as this stance m ay hav e been. As aconsequence, handy sticks or bones were picked up as defense weapons. Stone-throwing and club-swinging could only have been effective from a standingposition according to Dart (p . 202). Anatomical changes facilitating more up-right standin g an d locomotion came as a result of nat ura l selection under theseconditions. For D ar t, th e persistent use of these weapons was the only hab itcapab le of sh ifting th e weight of ape s from th eir knuckles an d bu tto ck bo nesonto their feet (p. 124). Meanwhile, a skull perched o n top of t he spineceased to be useful for the aggressive use of th e jaws. Ev idence for a d en tal re-duction already underway among the prehominids prior to their as sum ptionof regular bipedalism would stren gth en this reasoning. With small canines anddiminished mandibles, the qua dru ped al ha bi t of leading with th e hea dwould cease to be advantageous.


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HEWES] Origin of Hominid Bipedalism 695Nevertheless, I am inclined to be skeptical of this argu m ent . I seriouslydou bt t h at th e primordial bipedal hominids were skilled hunte rs used to wield-ing clubs or spears or doing much real damage with stones. The archeologicalevidence suggests th a t effective tool using (a nd tool-transport) came a t a lat er

stage in human evolution. Adventitious tools and weapons were surely pickedUP now and then , as aids in the food quest or for defense, bu t this seems a n in-adeq uate m eans to transform an occasional and reluctan t biped into a n effi-cient, hab itua l one. I n view of t he hardships faced by modern pr im itive hun t-ers, it is hard to see how the South African man-apes could have survived asgenuine predators. Moclern hunters have a trouble som e tas k in sp ite of beingequipped with carefully prepared weapons used with the skill developed fromlong practice, their abi lity to use language to coordinate t he actio ns of a groupof pursue rs, their fre qu en t use of dogs, an d fire-not on ly for fire-drives (cf.Ste wa rt 1956) bu t in night-camps while in purs uit of game for several day s a t atime. Ev en if the australopithecines were effective hu nte rs, ill-equipped as theywere for it, big game hunting can hardly have been the principal subsistencepa tte rn of th e ground-dwelling, erect-walking or erect-running Pr im ate s fromwhich they apparently descended. A long preparatory phase is indicated, inwhich prehominid bipeds might have been meat a nd m arrow ea ters, bu t seldomactual hunters.Some theories of erect h um an pos tu re are based on the visual advantage ofbeing able t o survey th e surroundings (D ar t 1959a: 223) ; chimpanzees standu p fleetingly to scan th e countryside. Oakley (1954: 12; 1959a: 1) stresses th evalue of raising the level of vision by uprig ht posture du rin g move me ntsthroug h t all grass gaps between forest corridors, as a result of which bip edalabilities would have ha d selective advantages. Coon (1954: 14) suggests th atan emergent flesh-eating ground-dwelling ape would gain from an ability toscan the landscape for game. Howells feels that bipedalism was perhaps en-couraged by environments with high grass and only thin woods, like much ofpresent Africa, the high grass permitting the little apes to stand and walkerect (1959: 127). Le ak ey envisages bipedalism emerging in co nnectio n withflight from pre dato rs in high grass, which would induce a cursorial protohom i-nid to pop u p from time to time to keep his bearings on a safe tree, etc.; even-tually the head would be kept aloft continuously by bipedal running (1959).Vertical or near-vertical posture certainly seems related to visual activity insome animals-e.g., prairie dogs, an d something of t he sort may par tly explainth e emergence of bird s from bipedal, cursorial reptiles. It is curious, however,th at th e adv ant age s of bipedalism hav e not led to a more widespread adoptionof this hab it amon g boi h pre dat ors an d their prey in grassland environmen ts.Of course, Prim ates are far more dependent on vision th an a re othe r mam -mals. The olfactorily deficient Primates might find bipedalism under suchconditions more valuable than if they had noses like most other mammals.Undo ubtedly, vision has played some role in hominid bipedalism. Visual da taare extremely imp or tan t for th e spatial orientation of hu m ans , precariouslybalanced on two hind feet, in c ontrast to qu adru peds standing foursquare with


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606 A merican Anthropologist [63, 1961little effort. Orione (1950) has assembled data on the visual worlds of man andother mammals. The principal weakness in this visual argument seems to lie inthe sporadic nature of visual stimuli for bipedalism, in which hereditary pro-clivities favorable to szcstained bipedal locomotion would not have much chanceto be selectively favored. Existing monkeys and apes can stand up well enoughas it is for occasional visual surveys of their environments. Bears probablystand up even more frequently, and their ancestors have presumably beendoing so for several million years, but bears have not become habitual bipeds.Evidently sporadic, though admirable, bipedalism has not pu t enough strain onbear anatomy and physiology in all that time to elicit, through natural selec-tion, bipedal modifications in their pelves, limb-bones, and associated mus-culature.Mention of bears and bipedalism suggests the adoption of bipedal stance orgait as a part of bluff or threatening behavior, as in the habit of male go-rillas when charging Life magazine 1960; cf. Dar t 1959a). A female Japanesemacaque studied a t the University of Colorado has been observed standingfully upright and unsupported when in an apparently threatening mood towardsafely caged Cynomolgus monkeys. Standing u p makes any animal look largerin the eyes of an observer, and thus more formidable. Lorenz and Tinbergenhave elegantly analyzed analogous threat postures in birds.Portmann (n.d.: 183) has dealt with other aspects of the visual world andanimal form. He notes that animals with the most complex cerebralizationhave heads most sharply distinguishable (p. 211). Mans upright posture dra-matically emphasizes the head-pole of the body, though perhaps no more thanantlers do for many deer. Piveteau (1957:315) recalls that erect posture wasthe hallmark of mankind for Aristotle, who believed that human thinking wassomehow related to it . Human beings are proud of their erect posture, writesDart (1959a: 223) in calling attention to the symbolic value of bipedalism.Patrides traces Renaissance ideas on mans upright posture (1958). It doesseem significant tha t the genital pole (Portmanns terminology) in man ispresented in the frontal plane, along with the expressive aspect of the head.The rump area, so prominent visually in Old World monkeys and apes, hasbeen tremendously transformed by the expansion of the gluteus muscles as afunction of bipedalism. Freud (1930:66) also remarked on this shift of thegenitalia to the frontal plane, and the later visual emphasis provided by thepubic hair, contrasting with the relative hairlessness of the rest of the trunk.The permanently enlarged female breasts in the same frontal plane are alsowithout parallel among other Primates. Etkin (1954: 138) suggests that im-portant socio-psychological changes followed the assumption of ventral ratherthan dorsal habits of copulation in the protohominid bipeds, presumably con-comitant with increased cortical control of sexual behavior. These mat ters arecertainly somehow linked to the assumption of regular bipedalism, but theyappear to be consequences rather than causes. Their sexual-selective value, ifany, may have been a fairly rapid dividend of bipedalism, later enhanced bythe drastic thinning of body hair.


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HEWES] Origin of Hominid Bipedalism 69The evolution of the Pinnipedia from doglike or bearlike ancestors offers an

instructive parallel to the problem of hominization (cf. Davies 1958). Sealsand sea-lions are a suborder of Carnivora whose ancestors took to the waterand in time became specialized swimmers and aquatic feeders. In explainingtheir evolution, it is unnecessary to account for the swimming abilities of thedog-bear ancestors. The Polar bear swims very well indeed From the availableevidence it seems clear that the Pinnipedia emerged as a result of: (a) life in anenvironment, probably around the shores of the Tertiary Arctic Basin, whichprovided diminishing opportunities for preying on land animals, but (b) in-creasing opportunities for a diet of fish and other aquatic animals, (c) on thepart of carnivores with swimming abilities equivalent to those of many otherterrestrial carnivores whose descendants never developed into aquatic mammals,(d) possessing fur and subcutaneous fat with excellent insulating qualities forterrestrial life under subarctic conditions, transferable to aquatic life in veryCold waters, and, very important, (e) without effective competition in thisparticular ecological niche. This digression is to focus attention on the centralquestion in the origin of hominid bipedalism : what were the external ecologicalconditions under which it would have paid off in terms of biological advantageto adopt a new way of life involving only the increased use of a behavioralcapacity already present but previously infrequently utilized?Spuhler comes close to my hypothesis when he says 1959:6): The changeto a partially carnivorous diet had extremely broad implications for the socialorganization of the early hominoids. Carnivores get a large supply of calories ateach kill. This concentrated food is more easily transported [my italics] t o a cen-tral, continually used shelter than is a low-calorie plant food, especially be-fore containers were available. Compact animal protein high in calories isa good basis for food sharing. Eiseley, too, approaches the central point inthis hypothesis, when he says, after stating the difficulty in seeing preciselywhy only one group took to bipedalism (1953:70): Some factor coming atjust the right time in mans anatomical evolution must have provided theimpetus for a new adjustment. so that, with the hands divorced fromthe job of locomotion, the new upright ancestral hominid could move thingsfrom place to place. Eiseley did not labor this point, but I intend to, since theorigin of the bipedal habit seems to me to lie in this moving of things fr om placet o place. Dart (1959a: 223) mentions transport habi ts as differentiating humanchildren from chimpanzees of the same age; humans carry, drag, or manipu-late objects while upright, whereas young apes prefer to carry in the mouth orto drag with one foot. Modern human children have relatively smaller andweaker jaws than young apes, but at the Australopithecus level such differ-ences were not so striking, although bipedalism had already developed. Kohlermentions that his Chimpanzees walked upright when their hands were full(1959:278-79), and that two of them stood up to collect large bundles of greenweeds and would then rush into their dens thus loaded (p. 245). Leakey 1959)observed such behavior in his pet baboon when carrying ears of maize, and wehave seen such behavior repeatedly in stumptail macaques being studied at


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698 American Anthropologist [63, 1961the U niversity of Colorado. D a r t sta tes (1959b) t h a t he ma y not ha ve givensufficient weight to burden carrying as an operative factor in the assumptionof erect posture, though he feels that weapon carrying and food transportwould have been concurrent behaviors.I believe that the only activity likely to have had the capacity to trans-form a mainly quadrupedal ground-dwelling Primate into an habitual bipedwould have been food tran sp or t from th e places where food was obtained to ahome base where it was consumed. Such carrying could only be accomplishedefficiently by an animal with arms and hands for grasping and holding. Mostmammals carry things, including their young, with their teeth and jaws; eventarsiers do this. B ut size an d weight limits for mandibular tra ns po rt are muchlower th an for loads borne on th e back, shoulders, head , or clasped against theside or chest. Primates above the Prosimii regularly assist with hands andarm s in the tran spo rt of nursing inf ants (Jones 1926: 148). Dorsal carriage ofburdens might be related to experience with carrying infants on the back, butexperiments with stum ptai l macaques suggest t h at th e less efficient clasping ofthe burden against the chest or side comes more naturally. D a r t thinks infan tcarrying habits might have played a n impo rtan t role in later burden carryin g,especially in open range environments, an d when infan t dependency ha d beenprolonged (19.5913). E tk in (1954: 135-36) no tes t h a t in m acaqu es a nd babo onsthe young are no hindrance to their mothers who carry them while foragingfor plan t foods. Bu t the ad vent of hun ting m ight have led to a sexual divisionof labor. Other mam malian p red ator s do no t hu nt w ith their young clinging totheir bodies, and protohominid females thus encumbered would have beenrat he r ineffective hunters. Loads too he avy t o carry in th e jaws can of coursebe simply dragged along, by m ou th in th e case of most quad rupe ds, or with onehan d (or foot) in the case of Pri m ates , thu s avoiding a need to walk upright.Ap art from the abrasion of the load , dragging is inefficient at distances on theorder of a mile or more, except ov er unusua l surfaces such as smoo th ice or san d.Le t us assume th at the burdens transported by the emergent bipedal proto-hom inids consisted of animal carcasses or larg e pa rt s thereof-whole limbs,hindquarters, heads, etc. Eiseley (1953) suggests that carrion-robbery mayhave been impo rtan t in hum an evolution, an d Bartholomew an d Birdsell sup-pose that the Australopithecinae were regular scavengers (1953 : 90). Oakley(1959a: 7) sees the protohom inids using tact ics of in tim ida tion to facilit atetheir scavenging, prior to the shift to regular hunting of large game. J. D .Clark (1960:311-12) also sup po rts th e scavenging theo ry, noting t h at somerecent primitives such as the Strandlooper Hottentot practiced it , and theMashi River people (Bechuanaland) locate carrion by watching the flightpa t te rns of vultures. D ar t has called repeated att en tio n to the bone-collectingproclivities of th e Australopith ecinae (1956a, 1958a), ta ki ng pains to showthat hyenas cannot have been responsible for the selective accumulations ofbone represen ted in the bone-breccias of t h e rock-shelters occupied by t heman-apes (cf. Howell 1959: 838). He has also tr ied to dem on strate the artif ac-tua l natu re of wh at he calls osteodontokeratic material (b ut cf Washburn


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H E W E S ] Origin of Hominid Bipedalism 6991957). The tool-making capacities of Lower Pleistocene hominids have beenconfirmed by the Zinjanthropus finds (Leakey 1960: 24-25), but the bone-breccias must mainly represent the left-overs of carnivorous meals. The bonemasses are testimony of transport, from hunting or scavenging territoriesprobably many miles in diameter. Washburn remains doubtful about theimportance of carrion scavenging in protohominid evolution, and his recentexperience in African game-reserves led him t o suggest that there would nothave been enough carrion around to support a terrestrial Primate population(1960a). Against this one must place the fact that vultures and hyenas are notrare animals, and that they and their ancestors have found enough carrion tolive on for a good many million years.If certain pre- or protohominids came to live off carrion, why would it havebeen necessary for them to transport fragments of it back to their dens or lairs?Why would they not simply have consumed it on the spot? For such a diet toprovide the mechanism for converting quadrupeds into bipeds, we have to as-sume that food transport became a necessary and regular part of the new feed-ing pattern. For a terrestrial Primate turned carrion-robber, there would havebeen an element of danger in hanging around a kill-site, to which the originalpredator might at any moment return for more feeding. This would be moreperilous than for vultures, which, unless fully gorged, can make an airborneretreat, or for hyenas who can trot off at high speed. But the major reason whya Primate carrion-eater would tend to carry his food home would be because ofthe inadequacy of Primate teeth for cracking bones and dissecting tough com-binations of hide, flesh, and tendon. Vultures are toothless, to be sure, bu t theyhave hard, sharp raptorial beaks and claws. T o maximize the food value ofmeat and marrow, a Primate must work deliberately picking, gnawing, andchewing slowly. Experience with feeding raw meat and bones to our stumptailmacaques indicates that it takes them eight or twelve hours really to clean abeef joint and to remove the accessible marrow. In intact bones, the marrowcould only be reached by cracking or smashing the bones against rocks, otherbones, or with hammerstones-behavior so far not exhibited by our macaques.A macaque handles the problem of getting meat off a bone in much the sameway that a human does, making no attempt to crush it with the teeth.The initial food-transport technique need not have been expert. It is likelythat spurts of running with the load clasped against the chest, as we have seenin macaques, came before the development of an even-paced stride with a well-balanced load. Running rather than walking, for an animal not yet anatomi-cally well adapted to upright locomotion, would be easier on account of thearrangement and function of the leg muscles (Hexton 1947). Washburn(1953: 503; 1960b: 67) thinks tha t even the Australopithecinae may have beenbipedal runners rather than walkers. W. E. L. Clark (1955:169-70) feels tha tthe ancestral Miocene and Pliocene apes were like modern cercopithecoid mon-keys scampering on the ground. Oakley (1959a: 1 suggests that one of them,Proconsul, could probably run short distances bipedally. If Proconsul loco-motor capabilities resembled those of the modern stumptail macaques, this


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700 A mericaia A nthropologist [63, 1961must have been a cer tainty. Since bipedal walkers tend to fal l forward, andbipedal monkeys suffer more f rom this m echanical disadvantage t ha n d o hu-ma ns with their well balanced skulls an d reduced jaw s, moving th e ce nter ofgrav ity backw ard b y carrying loads dorsally-on the bac k or shoulders-would h ave enh anc ed the efficiency of t he new g ait. Th e n at ur al wa ys ofcarrying heavy, bulky objects among bipedal Pr imates (observable in mon-keys, apes, young humans, and in any humans where the dis tance is qui teshort ) are by holding the burden against the chest , abdomen, or against theside, unde r one arm . M ore efficient modes of carry ing loads dorsally, used b yall human carriers who have to transport heavy burdens over long distances,with or witho ut th e aid of s trap s, slings, etc., seem to be learn ed with g reate rdifficulty. B ut it is a t least possible t h a t the inv entio n of dorsal load-carryingcame rather early in the history of hominid bipedalism, an d th a t i ts ado ptionmight have helped t o stabi l ize the bipedal habi t , thus intensifying and ac-celerating the ope ration of natu ral selective facto rs called in to pla y b y thisnew locomo tor patte rn.T h e effectiveness of an y new technique for exploit ing food resources is re-lated t o body size (Eiseley 1953). T o take m uch a dva ntag e of the carrion of thelarge herbivores, including the necessity of com peting with oth er diu rnalfeeders such as vultures, would probably have required a bo dy size of fr om 25to 5 kilograms. B u t an an imal of th a t size would ha ve t o roam fairly widely tofind enough to e at in a park-savannah landscape. In this connect ion we mustremind ourselves that neither the South African man-apes nor Zinjanthropus(with his specialized environ me nt an d app aren tly l imited flesh d iet) representreally e arly stages of hom inid bipedal evo lution.This leads us to the environmental problem. Changes of hab i tat are am ongthe prime movers of biological evolution. Contemporary paleoanthropologicalopinion places the tran sit ion to hominid sta tus in tropical park-sav annah land s,where narrow forest environments extend along river-courses, f lanked bygrassy plains (Washburn and Howell 1960:37) . Adaptat ion to such forestmargins, according to Oakley (1959a:S) led to a more varied diet , and to achangeover from plant-eating to meat-eating. There is some paleontologicalevidence for this environmental si tuation as far back as Proconsul (W. E. L.Clark 1952) . Clark notes that gal lery forests separated by open veld mustsomehow have been related to t he emergence of b ipedalism (1955: 169-70);movement f rom one forest c lump to the next would have, he thinks, s t imu-lated bipedal locomotion. Indeed, he suggests a paral lel to the argumentadva nced by Rom er to accoun t for the adoption of terrestrial l ife b y theAmphibia, forced t o m ove over land from one pond to anoth er in ar id environ-m ents . Pivete au (1957:648) refers to this no tion of the origin of b ipedalism as aparadoxical effort on the p ar t of the P rim ates concerned to regain arborealhabi tats separated b y open grasslands. It is well known th a t th e worlds grass-lands expanded enormously in T er t iary t imes, and th at rapid radial evolut ionof highly efficient grass-eating ungulates was und erwa y dur ing th e ap pro priatephase s of P rim ate evo lution. Such herd s of he rbivores were preyed up on b y


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HEWES] Origin of Hominid Bipedalism 701efficient carnivores, notably felids. Suitably generalized apes almost certainlyhave dwelt in the narrow bottom-land forest prongs which penetrated theseherbivore-rich grassy plains. A long list of authorities accepts this generalpicture (Gregory 1951534-35; Hill 1954: 100-01; Howell 1954:383; W. E. L.Clark 1955: 153-4,170; Teilhard de Chardin 1956; Bartholomew and Birdsell1953; Eiseley 1953; Oakley 1957: 20-21,1959a: ; Leakey 1959). We need notdwell on the earlier speculations concerned with the supposed effects of theHimalayan orogeny on hominid emergence, but it must not be forgotten thatan anthropoid mandibular fragment was found in Kansu by the Sino-SwedishExpedition, and that in spite of the more numerous finds in East and SouthAfrica, anthropoid evolution was underway on a broad front in South andSoutheast Asia (Simons 1960: 184,190-91). East and South Africa may wellhave been the locus for the appearance of bipedal hominoids, bu t suitable en-vironments and potential candidates probably existed from southern Europeand North Africa t o Southeast Asia as well. A museum handbook on evolution(British Museum 1958: 82) discussing Proconsul, suggests that volcano-setforest fires may have driven gallery-forest dwelling Primates out into opencountry where they became exposed to different conditions of natural selec-tion. It seems more plausible to attribute the shift to more open country tochanges in climate and availability of food than to the locally dramatic effectsof forest fires started by volcanoes.

An environmental stimulus to explore the grassland margins of galleryforests would have been an increase in the climatic distinctiveness of a wet anddry season. Oakley stresses the role of seasonal drought in driving a proto-hominid t o experiment with meat-eating in a country like the modern EastAfrican savannah (1953: 28-29,236; 1957:20-21; 1959a:6), noting that ba-boons may kill small game or eat carrion during droughts. In such regions, theannual dry season diminishes the availability of much of the vegetal materialon which Primates normally feed. At the same time, herds of herbivores movein toward permanent watercourses and water holes, and in times of reallyserious drought, actually crowd into such refuges. Here they are pursued bytheir regular predators, so that during the dry season, kills tend to be madeconveniently close to the gallery-forest homes of our postulated generalizedapes. Half-consumed carcasses of big ungulates would have thus been avail-able, not miles out in the open, parched plains, but in the river bottoms andparklands bordering stream courses. The first Primates to become accustomedto this new kind of food would have embarked on a momentous journey (cf.Dart 1959a: 197).Apes and monkeys will kill small animals for food (Spuhler 1959). In captiv-ity, some Primates come to relish meat, and some have been raised on a fleshdiet (Yerkes and Yerkes 1929). Coon (1959) mentions use of a meat cake forfeeding apes in the Philadelphia Zoo. Our stumptail macaques in Colorado willeat meat readily, and they are willing to go to considerable time and trouble toget it off bones and out of joints. Engels believed th at a changed diet, resultingfrom a predatory (i.e., meat-eating) economy, would alter the blood (i.e.,


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702 America n Anthropologist [63, 1961physiological status) of an animal, and thus play a role in evolutionary trans-formation. It does seem reasonable to suppose that a drastic dietary change,maintained for a sufficiently long time, would entail physiological changes uponthe basis of which natural selection would work with different pressures thanbefore. Meat, including marrow, fat, and various internal organs, provides arich diet for Primates, and also supplies salt. The increased energy obtainablefrom a meat diet, compared to the low-grade roughage usually consumed byPrimates, would in itself have been significant. Oakley mentions Reichenows1920 study in which a craving for meat was observed among captive gorillas,explained as a consequence of change in intestinal flora and fauna (Oakley1959a: 11-12). Such an alternation of the intestinal biota might well be broughtabout during long droughts.Sudden changes in food habits are not unknown among wild monkeys.Field studies of Japanese macaques have shown how a new food, sweet potato,came to be adopted by an entire local group through rapid social learning(Imanishi 1957; Yamada 1957; Itani 1955). It is reasonable to suppose thatour Primate ancestors occasionally tried out new foods. The crab-eatingmacaques are surely the result of a shift in food habits which has becomestabilized, but probably not genetically. Haldane (1956: 10) emphasizes theevolutionary importance of occasional inuentions, new habitual actions orkriyas as he calls them, adapting a Sanskrit word. The European ti t, Parusmajor, has recently invented a method of removing milk-bottle lids to get atthe cream in bottles left on doorsteps by milkmen. This kriya has spread tourban members of the species in many parts of northwestern Europe. A Pri-mate species ought to be able to match this performance under appropriateconditions. Scott (1958: 249), referring to the role of social learning in animalevolution, suggests that species with a highly developed social organizationautomatically provide a situation in which the social environment, producedin part by its own heredity, becomes one of the most important forces ofnatural selection. All these considerations lead to the conclusion tha t thereare types of social organization and population structure which are favorablet o rapid evolutionary change. The point is that successful experimentswith new foods would tend to spread quickly within socially integrated Pri-mate groups, and tha t if transport of a new food resource entailed bipedallocomotion, this too might diffuse rapidly (cf. Mayr 1960:371).It could be objected that other Primates have taken to the ground in dryparkland environments, but far from becoming cultured bipeds, they have infact become more specialized for quadrupedalism. Hooton (1925) felt that thefailure of the ancestors of the baboons to develop into bipeds was a seriousdefect in any theory which derives bipedalism simply from conditions of lifein an open terrestrial environment, but he offered no explanation for what hetermed the unfortunate choice of the cynomorphs. Oakley suggests tha t theancestors of the baboons must have had enlarged teeth when they descendedto the ground, whereas the ancestors of man may have started undergoingtooth and jaw reduction prior to abandoning arboreal life (1954). More


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HEWES] Origilz of ominid Bipedalism 703plausibly, Coon argues (1954: 13) th at there m ay h av e been an initial ecologi-cal differe ntiation, with the proto-baboons moving into rocky, rough terrain,whereas th e protohominids ada pte d themselves t o genuinely flat country .Baboon social organization m ay hav e also played a par t ; no other P rimates goto such extremes in maintaining male dominance b y the thre at to use theirhuge canines and long, powerful jaws. But my notion that baboons wouldmake in ade qu ate bipeds was rudely shaken by th e recent spectacle of a t roupeof ba boo ns exhibited by a circus in Lim a, Peru. W ith astonish ing ease, thoug hund ou bte dly the result of pat ient tr aini ng , these baboons walked and ranab ou t as perfect bipeds, with no trace of the awk wardness th a t Sam uel Johnsonnoted in dogs trained t o bipedalism. Between their turn s they sa t quietly onchairs, with less wriggling th an in a com parable gro up of h um an child ren. Aftertheir ac t, they left the ring in the qu adrup edal gait, which reassured me t ha ttheir remarkable bipedalism had no t been surgically induced.Mivart had raised a similar objection years ago in asking why, if highbrowsing were such an advantage, other ungulates beside the giraffe had notacquired giraffe-like necks. Darwins reply was very reasonable, and Mayrbrings it u p to da te (1960:376). We need not be embarrassed b y th e coexistenceof baboons an d australopithecines. I n a ny case, the l att er ha d long been bipedalan d were qu ite capable of moving int o area s occupied by baboons. Oncefirmly established, a carrion eating habit would encourage a widely spacedty pe of t errito rialit y, promoting the hominid propensity for expansion i nt o avariety of environments which would have become more marked with theadoption of big game hu nti ng (Bartholomew a nd B irdsell 1953:487) .Out of the ha bit of carrying carrion to a lair could have arisen the firstregular rat he r th an sp oradic use of tools. If we assume for th e protohominidsan intellectual level ab ou t equal to t h a t of mod ern apes, no special changeswould hav e been needed in eith er han d or brain to m ake possible this new kriy aor learned behavior (Jones 1926; Oakley 1954: 10-11; W ash bu rn a nd Avis1958:432). Tools would come to be used regularly t the lair because theywould lie conveniently s catt ered ab ou t there alr ead y, in the form of bones,horns, antler s, mandibles with teeth , etc., from previous meals, an d also in theform of sh arp-edged rocks if th e lair hap pen ed to be a shelter in suitab le bed-rock. T hi s use of tools dem and s no foresight (H ock ett 1960:95). Ev en dogsreadily use artif acts ordinarily present in their homes (bla nke ts, drinkingvessels, toys, etc.), though they are unlikely to carr y such ob jects to dis tan tplaces in expectation of their fut ur e usefulness a t some ind eter m inat e op-portunity. Butchery at kill-sites or carrion-sites would have to depend for along time not on tools purposely brought into the field, but upon objectshappened upon aro un d the kill, such as fractu red pebbles or sticks, or th e bones,horns, and hooves of th e carcass itself (D ar t 1956b). D a r t rejects the idea th atprimordial tool-using, or even tool-making, to a pattern requires speech; hebelieves it could be perpetu ated by observation and imitatio n, without verbalinstr uct ion (1959a:318). I incline to agree. Social fac tors ca nn ot be excludedfrom th e effort to explain hominization, b ut the principle of parsimony would


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704 American Anthropologist [63, 1961suggest that we should not exaggerate the possible social differences betweenthe earliest protohom inids an d existing pongids.Spuhler 1959) considers changes in social life which might have followedassumption of a m eat d iet, noting t ha t only carnivores sha re their food (cf.Sahlins 1959). Sharing of natural foodstuffs should be viewed more as a mat te rof packaging and consumption techniques than of altruistic action or a mutua laid device for achieving social solidarity. Carnivorous mammals sharechiefly because th e carcasses of large beasts a re sim ply too big t o monopolize.Herbivores do not share because their food is in dispersed bits, and not inchunks. If enough of a carcass were carried home by a meat-eating Primate,the meal would ten d to be unaltruistically a nd unequally shared by th efamily or band m embers present, provided th ey were hu ngr y and agile enoughto sna tch portions away from the individual who brought i t home. B ut com-pared to the individualistic food grubbing practices of vegetarian Primates,even this i nad ver tent sharing would confer biological adv ant age s in th e fo rm ofimproved family nutrition, reduced infant mortality, etc. In time, naturalselection might reduce aggressiveness and individualism during meals, thoughmodern hu m an behavior under conditions of food shortage indicates th at therem ay not h ave been no table progress along this line.Bartholomew and Birdsell 1953 : 84) suppose that protohominids lived insemi-permanent family groups, whereas Etkin prefers a wolf-pack analogy1954:136). In an y case, both because of g rea ter size an d s tren gth , an d be-cause females would be encumbered by nurslings an d pregnancy, males wouldten d t o be the more efficient food-transporters, th us laying the fou nd atio n forth e late r division of food-gathering lab or un de r cond itions of ac tu al hu n t-ing.Language probably emerged long after bipedalism, whether or not ourhypothesis of a relation between bipedalism and food-transport can be verified.D uB rul has recently elaborated a n attr ac tiv e hypothesis for th e emergence ofspeech as a by-product of the erect posture 1958). Oral evolution in ou r Orderas a whole has been affected b y P rim ate collection a nd p rep arati on of foo d foringestion with the hands, and not directly with the mouth. According toD uB rul, the anatomical modifications necessary for articu late speech (a nd no tmerely vocalization) depend on changes in th e relation of m ou th pa rts to thebreathing app ara tus consequent upon bipedal posture and th e resultant changein placement of t he head, along with sno ut reduction. D uB rul m eets the usualobjectors who point to articulate speech mimicry in certain birds by showingth at these birds have mouth an d thr oat structures analogous to mans, thoughnot derived from achievement of upright posture (p. 38). I think i t likely tha tregular linguistic communication arose in connection with the only activity ofearly man sufficiently complex to require a fairly extensive vocabulary ofsymbo ls: the h un ting of large ungulates collaboratively ( bu t cf. Ho cke tt 1960).Etkin 1954: 136) feels th a t language of some sort would hav e been imp or tan tfor a pack-hunter anthropoid. Dart disagrees, pointing to collaborativehunting by speechless lions, wolves, etc., where silence seems advantageous.B ut the genuine carnivora have a highly developed sense of smell for guidance


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HEWES] Origin of Hominid Bipedadism 705to their prey, extremely effective personal armament, and some can move a tvery high speeds. Proto-human hunters without dogs, fire, or projectile weap-ons can be truly successful hunters only by outwitting and wearing out theirvictims, especially by pursuing them in small groups. In the vicinity of thequarry, the collaborative hunting language may well have been gestural ratherthan vocal. Before ending these remarks on language, which were to show itspossible relationship to bipedalism, let me suggest the possibility of setting upan operations research or systems analysis project on the logical properties ofproto-hominid big game hunting, given a knowledge of the weapons available,behavior of various ungulates in certain kinds of terrain, etc. The results couldindicate the essential characteristics of any language or symbol-system neces-sary for economically effective big game hunting a t a pebble-tool technologicallevel. Scott (1958: 250) believes that once verbal communication had appearedin small hominid bands, partially isolated by language itself from other simi-larly constituted hunting groups, evolutionary change would tend to be veryrapid indeed.

At the beginning of this paper I said that the problem of the origin ofhominid bipedalism could be attacked in part by experiments (cf. Washburn1951:76). A small pilot s tudy has been started in the Department of Anthro-pology a t the University of Colorado, on a research grant supplied by theUniversitys Committee on Research and Creative Work, using two stumptailmonkeys. These virtually tailless, sturdily built, semi-terrestrial macaquesprobably approach sufficiently closely the character of the Miocene or Pliocenestock from which the habitually bipedal protohominids evolved, and for thiskind of study they may be superior to anthropoid apes. We are trying to deter-mine what kinds of external conditions most facilitate bipedal locomotion,including the carrying of food-burdens, and the effects of different terrain andground-cover, The results so far are encouraging, though our data consistmainly of still and some motion picture records (Fig. la,b) . We are also inter-ested in meat-eating and bone-handling behavior. I n view of the assertions inthe literature that nonhuman Primates can maintain bipedal gait for onlyshort distances, we are also interested in determining just how far a wellmotivated macaque can travel, once accustomed to walking upright, withoutsigns of extreme fatigue or rebellion. Eventually, with animals raised andtrained to bipedalism from childhood, it might be possible to detect changes inmuscle and bone growth (cf. Bunak, in Delmas, 1958:33). Comparative studiesof several species might reveal the existence of hereditary variations facilitat-ing bipedalism in certain species.

N O T EThis is a revised version of a paper read a t the 58th Annu al Meeting of the AmericanAnthropolog ical Association, Mexico, D.F., 1959.

As indicated in the bibliography, I have received useful comments and suggestions from anumber of colleagues; naturally I am responsible for any misuse I may have made of these ideas.I am particularly grateful to A. J. Kelso and H. Rodeck of the University of Co lorado , and W. Wil-son of B ryn M aw r, for their reading of the penultimate d raft of this paper, to S Asmus for Figurelc., and to E. C. Templeton for indispensable assistance w ith the experimental n~acaques.


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706 American Anthropologist [63, 1961REFERENCES CITED

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