SEVEN DECADES OF EAST AFRICANMIOCENE ANTHROPOID STUDIESRussell H. Tutt - PDF document

SEVEN DECADES OF EAST AFRICANMIOCENE ANTHROPOID STUDIESRussell H. Tuttle*and South Asia. Indeed, Eurasian fossil apes were collected decades before the Darwinianis the first fossil primate known to Western science. EdouardLartet discovered the type mandible near Sansan, France, in 1834; and, the Eppelsheimfemur, which resembles Slovakian femora of , was found in Germany in 1820(Piveteau, 1957; Pohlig, 1895; McHenry and Corruccini, 1976).South Asian Miocene anthropoids came to the attention of the wider scientific com-munity when Pilgrim published findings on them in the 1910s. Vertebrate faunas had beencollected from the Siwaliks by Falconer and Cautley (1830…1850) for the British Museumand by Richard Lydekker (1876…1886) and Guy Pilgrim (1900…1930) for the GeologicalSurvey of India Museum in Calcutta. Barnum Brown collected for the American Museumof Natural History in 1922…23 and G. Edward Lewis collected for the Yale Peabody Mu-seum in 1931…33. In 1935, DeTerra collected specimens with the Yale…Cambridge IndiaThe earliest studies of African Miocene anthropoid primates were focused on westernKenyan specimens. In 1933, A. Tindell Hopwood of the British Museum diagnosed adozen dental and gnathic specimens that had been collected between 1926 and 1931 in theHopwood considered that both species represented extinct lineages. He named the re-Proconsul africanus and concluded that they were related to and were ancestral to Pan troglodytes. Thus began the search-for-the-su-perlative period, in which researchers strove to link novel specimens directly to extant* Russell H. Tuttle, Department of Anthropology, The University of Chicago, 1126 E. 59th Street, Chicago, IL 2. COLLECTION AND INTERPRETATION: 1931…1959In 1931 and 1932, Louis Leakey, Donald MacInnes, and other members of the third EastAfrican Archaeological Expedition discovered Miocene anthropoid fossils on Rusinga Is-land, at the mouth of the Winam Gulf in Lake Victoria, and at Songhor, on the mainland, afew miles north of Koru. Leakey, MacInnes, and other scientists continued to revisit Rusingathe 1930s and 1940s (L. Leakey, 1937; M. Leakey, 1984; MacInnes, 1943). In 1948, aIn 1951, Wilfrid LeGros Clark and Louis Leakey published a detailed monograph on theIsland, Maboko Island, Songhor, Koru and Lothidok. They consisted mostly of fragmen-tary lower and upper jaws and isolated teeth. Few of the upper and lower dentitions couldbe associated with confidence as belonging to the same individual. A notable exception isProconsul heseloni, which was discovered in 1948 on Rusinga Island by MaryLeakey. Postcranial remains were quite rare and generally fragmentary.Clark and Leakey (1951) diagnosed four species of dentally great ape-like forms: and small, medium and large species of Proconsul:Proconsulafricanus, Proconsul nyanzae, Proconsul major, respectively. They further diagnosedtwo species of dentally gibbon-like forms: With Hopwoods concurrence, they sank Proconsul africanus.Clark and Leakey (1951) concluded that species of belong to theHylobatidae, and though somewhat inclined to create a new subfamily for Proconsul Propliopithecus hylobatine apes like Proconsul was derived from them.represented not greatly modified sur-Proconsul emerged. They considered Proconsulto be a probable ancestor of modern African apes, but they did not designate which speciesProconsul may have given rise to may havebeen ancestral to and ultimately, through , to modern lesser apes.They considered to be the most likely ancestor of the EurasianClark and Leakey (1951) were not specific about possible ancestry of the Hominidae.Asian and African apes. In their scheme, hominid evolution did not include a brachiatingphase. Instead, there was a direct transformation of limbs like those of Proconsul In 1948, Louis Leakey discovered associated jaws and limb bones of at least fourin a block of limestone on Rusinga Island. They weremonographed by Clark and Thomas in 1951 and were restudied by Denise Ferembach(1958). Clark and Thomas (1951, p. 12) concluded that the posture and gait ofR. H. TUTTLE probably resembled the quadrupedal monkeys rather than the brachiatingWith the addition of two rib fragments, a badly damaged fragment of humeral shaft,and a fragment of scapula, Ferembach (1958) concluded that special affinity with hylobatid apes. Instead, she inferred that affinities with African pongid apes, especially chimpanzees. Further, she stated that filia-Limnopithecus legetet, Pliopithecus antiquusmodern hylobatid sort, and quadrupedism in trees; but they walked bipedally on the ground.dal. She simply surmised that they might have been bipedal because they lacked featuresIn 1951, on Rusinga Island, T. Whitworth collected postcranial bones of a subadultProconsulProconsul africanus. The specimens were monographed by Napier and Davis (1959),Proconsul africanus possessed many features that indicate arborealhabits, including both quadrupedism and some brachiation, but there was no direct evi-Three decades later, Alan Walker (1992) extracted several additional postcranial bonesfrom a block of limestone that had been returned by the British Museum to the NationalMuseums of Kenya. They belonged to the same individual [KNM-RU 2036] that Whitworthhad discovered in 1951. Further search on Rusinga Island also produced an informativeleg and foot, lacking phalanges, which were reasonably assigned to Proconsul nyanzae(Walker and Pickford 1983; Walker and Teaford 1988, 1989).3. TAXONOMIC SHUFFLES, ANCESTORS, AND FUNCTIONAL INTERPRETA-The period of initial description and taxonomy of the African Miocene anthropoids (1926…1959) was followed by taxonomic reassignments, somewhat more fine-grained functionalIn 1963, Elwyn Simons sank into , arguing that geographicgeneric status for primate species. Ten years later, Simons and Fleagle (1973, 140) with-drew this view, stating that although the dentitions of the two forms are indeed verysimilar, particularly in the lower molars, the skeletal evidence suggests that generic dis-tinction is indeed justified. Although difficult to evaluate quantitatively, the postcranialdifferences are certainly greater than those separating modern ape genera.Ž They con-SEVEN DECADES OF EAST AFRICAN MIOCENE ANTHROPOID STUDIES In 1977, Peter Andrews and Simons created a new genus for largely because its limb bones evinced greater development of suspensory behavior thanthose of other Miocene anthropoids. They renamed it Dendropithecus macinnesi. only postcranial features that they specifically mentioned in the diagnosis of DendropithecusProconsulIn 1983, Fleagle proffered that, like Dendropithecus macinnesi suspensory arboreal quadruped. Further, he concurred that Proconsul africanus Dendropithecus macinnesi On the other hand, on the basis of an allometric study of modern and Miocene anthro-poids and their limb proportions, Aiello (1981) concluded that while Proconsul africanuswere below-branch feeders, Dendropithecus were above-branch feeders.She further stated that Proconsul africanus was a more likely ancestral type for the extantJungers (1984) conducted an extensive allometric analysis of the locomotor skeletonsof anthropoid primates, leading him to conclude that Dendropithecus long limbs and were basically arboreal, suspensory, monkey-like creatures rather like without a prehensile tail. Also in contrast to Aiello (1981), Jungers (1984) concludedProconsul africanus had relatively short limbs and was a relatively slow-moving ar-boreal quadruped. Here he echoed Walker and Pickfords (1983) conclusions based onIn 1962 and 1963, Louis Leakey proposed the erection of a new family, the Proconsulidae,which would include the genus Proconsul and some specimens of and. He did not specify which individual fossils he would include in the newfamily. He commented that erection of the Proconsulidae was justified by the distinctivestructure of the canine teeth, the face, and, where known, the skull. In particular, he citedthe shape of the mandibular arch, the nature of the mandibular fossa, the absence of asimian shelf, and the special nature of the canine teeth (L. Leakey, 1963).On the basis of a comprehensive review of available fossil materials, in 1965 Simonsand Pilbeam sustained Gregory and Hellmans pongid subfamily, the Dryopithecinae, whichLeakey had termed a dust bin, and rejected Leakeys proposal for the Proconsulidae. In-deed, they pursued a course that was diametrically opposite to that of Leakey and sankProconsul Simons and Pilbeam (1965) retained the nomen Proconsul as a subgenus of Proconsul africanus, Proconsul nyanzae, Proconsul majorinto it. They arrived at this decision after systematically comparing Proconsul africanuswith the type specimens of . LeGros Clark, senior author of theProconsuland some maxillae attributed to Indian R. H. TUTTLE . Further, they concluded that there was no justification. Thus, they sankinto their newly created taxon, Simons and Pilbeam (1965) suggested that might be close toand thus remotely related to later Hominidae.las. They inferred that either Dryopithecus fontani Dryopithecus nyanzae were prob-In 1958, Walter Bishop recovered fragmentary mandibular and isolated dental specimens,which Louis Leakey identified preliminarily as Proconsul, respectively, on the flank of the Napak volcano in the Karamoja District of Uganda.Further, in 1961, Bishop and Whyte (1962) collected additional large hominoid specimens1961, David Allbrook collected more remains of a large hominoid at Moroto II (Allbrookand Bishop, 1963). During a 6-week period in 1963 and 1964, Bishop (1964) and com-pany systematically collected many mammalian remains from Napak and Moroto, includ-ing a well-preserved palate and snout with face present to the lower left orbit of a small. Fleagles (1975) preliminary commentson the palate from Napak IV were that the proportions of the maxillae, zygomatic bonesand teeth are much more similar to those of a living gibbon than those of specimen is virtually identical to living gibbons. . .although it is considerably smaller inIn 1969, Walker provisionally reported that specimens of among the fossils collected by Makerere University College expeditions, beginning in Micropithecus clarkibasis of dental and cranial bits from the Miocene deposits at Napak. They concluded thatit had greatest affinity with Dendropithecus macinnesi and that it had no clear link withPickford (1982) noted that if Micropithecus Dendropithecus bilophodonty into their molars, they would be viable ancestors for VictoriapithecusMiocene monkey that is especially abundant on Maboko Island. If this scenario werecorrect, the Cercopithecoidea evolved in Africa from small-bodied dental apes during theEarly Miocene. Six years later, Pickford and Senut (1988, p. 51) rejected the possibilitythat a species of East African Early Miocene anthropoid could have evolved intoVictoriapithecus because of the morphological distance between Victoriapithecus lower Miocene primates from West Kenya.ŽAt Moroto II, the 1963…64 expedition collected 56 additional pieces, which Bishop (1964)ascribed to the same individuals of Proconsul major as the 1961 palatal and mandibularSEVEN DECADES OF EAST AFRICAN MIOCENE ANTHROPOID STUDIES fragments. Allbrook and Bishop (1963) gave preliminary descriptions of the cranial re-mains. In 1968, Walker and Rose described remarkably African ape-like vertebral re-Proconsul constituted the primary empirical base for Pilbeams(1969) doctoral thesis at Yale University. He was inclined to associate the palate, twomandibular fragments and vertebral fragments from Moroto II as a single male ofDryopithecus (Proconsul) major. He concluded that all of the large hominoid specimensfrom the three Napak sites belong to . He described the face as ascaled-down long-snouted male gorilla with a gracile upper face. From the relatively low-matter.Pilbeams (1969) reassessment of Kenyan specimens of Proconsulindicated close morphological affinities and conspecific status among from Koru and Songhor and the large Ugandan hominoids. He concluded that probably represents remnant populations of the ancestral stock that gave rise to. Progressive adaptation to a tough vegetal diet on the heavily forestedGorilla gorilla. Pilbeams (1969) might well have been a knuckle-walker, though probably it was more active and less terrestrial than extant gorillas are.Pan troglodytes. that the lineages leading to modern chimpanzees and gorillas were specifically separated Pilbeam (1969) retreated from the assignment of certain medium-sized African speci-mens to (Simons and Pilbeam 1965) on the grounds that theywere probably earlier than the Indian forms, though he thought they might represent an-In 1994 and 1995, Gebo and coworkers (1997) collected additional postcranial speci-mens from Moroto I and II. Although dated at 20.6 Ma, they evidence more ape-likefeatures than any other Early or Middle Miocene anthropoid. Gebo et al. (1997) created aMorotopithecus bishopi, for the entire collection of large anthropoid speci-mens from Moroto. Unfortunately, they may have included a nonprimate scapular frag-ment (MUZM 60) in the hypodigm (Benefit, 1999;Pickford et al., 1999; Senut, 1999).Further, Gommery (2003) noted that there are two large hominoids represented at Moroto: (formerly Proconsul majorAfropithecus turkanensisMorotopithecus3.5 Fort Ternan�In 1961, Louis and Mary Leakey directed the collection of 1200 fossils at Fort Ternan,which is a few miles south of Koru. In 1962, Louis Leakey announced the discovery ofprimates there but concentrated on specimens that he diagnosed as He mentioned discovery of a very large upper canine, scarely [Proconsul nyanzae. . .Ž (L. Leakey, 1962, p. 690).In 1968, Leakey gave a brief report in Nature on the primates that were associated. He also mentioned isolated teeth and parts of two mandiblesR. H. TUTTLE of Hylobatidae that were too different to be assigned to �. He noted that there were 300 specimens of MioceneNature, Simons (1969) accepted the hylobatid status of the FortTernan specimens but referred them to because at the time he consideredOne mandibular specimen of a nonhylobatid primate from Fort Ternan evidenced asimian shelf and bicuspid P, features that Leakey (1968) had never observed in specimens Proconsul, but which occur in European and Asian . Therefore, he provi-sionally referred this new Fort Ternan specimen to . Leakey (1968) alsoProconsulSimons (1969) concurred that the new mandible from Fort Ternan was that of. But he suggested that thecanines should also be referred to because canines of Indianclosely resemble those of and it is un-Andrews and Walker (1976) concluded that, apart from hominoid species from the Fort Ternan deposits. Limnopithecus legetet common primate at the site. Fourteen specimens and probably many fewer individualsrepresented it. They concluded that Dryopithecus nyanzae was represented at FortTernan by 7 specimens. They provisionally recognized Proconsul Micropithecus Rangwapithecus gordoniProconsul sp., and an oreopithecoid at Fort Ternan. In 1992, HarrisonProconsul sp., probably Oreopithecus sp., and perhaps sp. in the FortTernan anthropoid sample.3.6 Taxonomic trials of the 1970sDuring the 1950s, 1960s, and sporadically thereafter, collecting continued at establishedeastern African Miocene localities and further primate remains were recovered from RusingaIsland, Songhor, Koru, and Maboko Island. Anthropoid fossils also were found on MfanganoIsland in the Winam Gulf of Lake Victoria. Andrews (1978) noted that the size of thefossil primate collection at the Centre for Prehistory and Palaeontology in Nairobi hadIn 1978, Andrews listed the following numbers of specimens: Species n Dendropithecus macinnesi160152Proconsul (Rangwapithecus) gordoni 79 78Proconsul (Rangwapithecus) vancouveringi 10 5136159Proconsul africanus120146Proconsul nyanzae109104Proconsul major 81 75 TOTAL700735SEVEN DECADES OF EAST AFRICAN MIOCENE ANTHROPOID STUDIES