Origins of New World monkeys

Fossil ceboid evidence is reviewed with reference to the origins and affinities of the New World monkeys. This evidence indicates that the ceboids evolved from a North American primate of omomyid-like form. The events of continental drift apparently had little to do with the origin and dispersion of the New World monkeys and direct relationships to the Old World monkeys are not indicated. Three of the five extant New World monkey subfamilies are represented in late Miocene deposits of South America and it appears that evolutionary events leading to extant Ceboidea occurred within the South American continent.     

Mechanisms of hominoid dispersal in Miocene East Africa

The thesis of this essay is that the ecological changes which occurred during the Miocene in East Africa, created both the need and the conditions for the development of dispersal behaviour and other adaptations. The major ecological change in East Africa during the Miocene was the break-up of the relatively homogenous, lowland, tropical rainforest. The forest break-up was due to the combined effects of climatic change and rifting. The result of the fragmentation for species adapted to the forest, was increasing resource limitation. Species responded either by retreating with the forests, becoming extinct, or by evolving or developing new behaviours to cope with the new environment. The focus of this paper is upon the development of dispersal as a behaviour pattern for locating patchy resources. An ecological model is advanced to explain the development of dispersal and to place it in the context of other competing evolutionary responses to the ecological changes of the Miocene. The anatomical evolution of the Old World monkeys and apes during the Miocene is looked at in terms of the model. Bovid evolution over the same period is also looked at as evidence of a broad, episodic turnover in response to the ecological changes. It is suggested that hominid bipedalism may also fit the model and may have evolved as an adaptation for dispersion.     

The phylogeny of Old World monkeys

The living Old World monkeys, family Cercopithecidae, are the most successful group of nonhuman primates alive today. Overall, they account for over one quarter of the extant genera of primates and approximately 40% of the species. They have an extensive fossil record extending back to the early and middle Miocene of Africa.^1,2 Despite this specific diversity and a long evolutionary history, it is commonly argued that the group is relatively uniform in both its skeletal³ and dental⁴ anatomy, suggesting that much of the current taxonomic diversity is a relatively recent phenomenon. In such a species group, it is perhaps not surprising that the taxonomy of Old World monkeys is subject to many differing classifications. Thus, in recent years, authors have recognized as few as 10 and as many as 22 different genera within the family. Although some of this greater-than-two-fold difference in the number of genera can be attributed to the “splitting” versus “lumping” philosophies of different researchers, much of it is based on major disagreements over phylogenetic relationships. Recent studies of the genetics and chromosomes of this group have illuminated Old World monkey phylogeny in many ways. Some of these studies have resolved longstanding debates based on morphological data; others have revealed phylogenetic relationships that morphologists had never suspected.     

Comparative assessment of the ischial morphology of Victoriapithecus macinnesi

An almost complete primate ischium was recovered from middle Miocene (ca. 15 ma) deposits of Maboko Island (Kenya) in 1987. The specimen shows numerous similarities to the ischial morphology of extant cercopithecids and is attributed to Victoriapithecus macinnesi (Von Koenigswald, 1969), the early Old World monkey best known from Maboko Island. The Victoriapithecus ischium provides the first evidence of early Old World monkey pelvic girdle anatomy. The ischium is characterized by an obliquely oriented and broadly flaring tuberosity, a relatively small acetabulum with little ventrally directed curvature of its caudal portion, a long ischial body and a flange-like ischial spine positioned caudal to the rim of the acetabulum. In these features, Victoriapithecus most closely resembles the vervet monkey, Cercopithecus aethiops. The fossil specimen indicates that Victoriapithecus possessed ischial callosities, a mobile tail and adaptations for (possibly cursorial) quadrupedalism with an adducted posture of the thigh. The occurrence of ischial callosities in Victoriapithecus extends the documented antiquity of this feature in catarrhines by more than 12 million years and shows that the distinctive “sitting-sleeping” adaptations of Old World monkeys (Washburn, 1957) originated prior to the divergence of Colobinae and Cercopithecinae. Differences of developmental sequence and tissue composition indicate that the ischial pads of cercopithecids, hylobatids, and pongids may have arisen independently, through parallel evolution. Contrary to Strasser and Delson (1987), discontinuity of ischial callosities was probably the primitive condition for male cercopithecids.     

Blood groups of Old World monkeys,evolutionary and taxonomic implications

For practical purposes two classes of blood groups of Old World monkeys can be distinguished: human-type and simian-type, depending on the kind of reagents used for testing. Of the human-type blood groups, only the A-B-O groups, defined by saliva inhibition and serum tests, are polymorphic in some, but not all, monkey species. The distributions of those groups show wide differences not only among monkey species but also among troops of one and the same species. The tests for other human-type antigens give with the monkey red cells either uniformly positive or uniformly negative results. Thus, the human-type blood groups seem to be of limited use as taxonomic tools in the systematics of the Old World monkeys.On the other hand, the simian-type blood groups, defined by isoor crossimmune monkey sera, display highly polymorphic patterns in most species of Old World monkeys, and the capability of the antisera to react with combining groups on the red cells of monkeys of closely related species seems to reflect the taxonomic closeness of two or more species. The fact that some of the simian-type specificities, notably those belonging to the rhesus D^rh graded blood group system, are shared by many species of Old World monkeys, indicates that they were introduced into genotypes during early stages of evolution of the Cercopithecidae.     

Simian homologues of human herpesvirus 8

Gamma-herpesviruses can be found in most primates including Old World an New World monkeys. The gamma-herpesvirinae are grouped into two classes: lymphocryptoviruses (gamma1) and rhadinoviruses (gamma2). The lymphocryptoviruses include Epstein-Barr virus, lymphocryptovirus of rhesus monkeys, and Herpesvirus papio of baboons. Rhadinoviruses that infect New World monkeys include Herpesvirus saimiri, whose natural host is the squirrel monkey, and Herpesvirus ateles, which infects spider monkeys. Rhadinoviruses that infect hominoids and Old World monkeys include Kaposi's sarcoma-associated herpesvirus, also known as HHV-8, and rhesus monkey rhadinovirus.     

EVOLUTION OF HORNS IN UNGULATES: ECOLOGY AND PALEOECOLOGY

(1) The savanna ungulate faunas of the North American Miocene were broadly similar to those of present-day East Africa in terms of overall morphological and taxonomic diversity. However, the predominant ungulates of the African faunas are bovids, which possess bony horns that are primitively sexually dimorphic in their occurrence. The predominant ungulates of the North American Tertiary were equids, camelids and oreodonts, which all lacked horns. A limited number of horned ruminants were present, but these were largely Miocene immigrants from Eurasia. Horns were also absent from the large-bodied herbivores in the endemic faunas of South America and Australia. (2) The absence of horns in equids and tylopod artiodactyls is unlikely to be due to genetic insufficiency. Bony horns were present in brontotheres, which were closely related to equids, and in protoceratids, which were closely related to camelids. Nasal horns were present in one oreodont genus. (3) Studies on living ungulates show that a strong correlation exists between habitat type, feeding behaviour, social behaviour and morphology. It is possible to use the morphological remains of extinct ungulates to reconstruct the types of feeding and social behaviour, and to use the distribution of morphologies and body sizes in a community of mammals, in conjunction with geological and paleobotanical evidence, to reconstruct the type of habitat. (4) The importance of the post-Eocene climatic changes to the history of mammalian evolution is stressed. Continents at higher latitudes have become increasingly seasonal in terms of temperature and rainfall since the equable global conditions of the early Tertiary. Savanna mosaic were the predominant biome in North America by the early Miocene, and in Eurasia by the middle Miocene. Living temperate-latitude species of ungulates may not be a reliable guide for the assessment of the interrelationship between behaviour and morphology in an evolutionary perspective, as their behaviour may have been recently adapted to a habitat type that has only been in existence since the Pleistocene. (5) The primitive condition in eupecorans and protoceratids is the absence of horns, with the presence of large sabre-like canines in the males. The first horned members of these divisions had horns in the males only. Small present-day antelope, where horns may also be present in the females of the species, are probably secondarily small. (6) Horns were acquired independently in ruminant artiodactyls at least three times, and a maximum number of seven times is not unlikely. In each case, horns first appeared at a critical body weight of about 18 kg, and in correlation with a change in habitat from closed to open woodland. (7) Horns in living ruminants are associated with territorial defence by males holding exclusive feeding and reproductive territories in woodland habitats. Such behaviour in present-day antelope is correlated with a body size of greater than 15 kg and a folivorous diet. It is argued that horns evolved in ruminant artiodactyls on the adoption of this type of territorial behaviour once the critical combination of body size, diet and habitat type had been attained in their evolution from small, essentially frugivorous, forest-dwelling animals. (8) Perissodactyls never evolved sexually dimorphic bony horns of the type seen in ruminant artiodactyls. This is because their foraging and digestive strategies necessitate a larger daily intake of food. In a woodland habitat they were never able to adopt a feeding area small enough to make exclusive territory maintenance an economical proposition. Territory holding in male perissodactyls is seen, but under the opposite conditions of habitat to territorial behaviour in ruminant artiodactyls. (9) Study of the morphology and paleoecology of oreodonts suggests that they were woodland herd-forming browsers with exclusively folivorous diets. They probably had some forestomach fermentation, but did not chew the cud. Similar studies of Tertiary camelids suggest that they were predominantly selective browsers eating herbage at a low level in open country and formed mixed-sex feeding groups. These combinations of feeding and social behaviour suggest a more open structure of the mid-Tertiary habitat in North America than in Eurasia. (10) Studies of the behaviour and morphology of living members of the Ruminantia, and of the morphology and paleoecology of their fossil ancestors, suggest that they were primitively tree browsers living in closed woodland habitats. Such habitats were abundant in the Old World, but in limited supply in North America during the Oligocene, where the protoceratids were the only ungulates to parallel the eupecoran type of feeding and social behaviour. South America appears to have had an even more open habitat in the Oligocene than North America, and no parallel to the eupecorans was seen amongst the indigenous ungulates. The radiation of the Bovidae into open grassy habitats in the Pliocene may have been dependent on the immigration of grazing equids into the Old World. (11) I conclude that there was a difference in habitat structure between North America and the Old World during the Tertiary. The food resources in North America were more widely dispersed, and this may have been the result of the trees being more widely spaced. A possible causal mechanism for this was the stable land mass of the North American continent during the Tertiary, resulting in a more continental climate, with a more severe effect of the post-Eocene seasonality on the vegetation. The faunal record of the two continents also implied a greater density of trees in the Old World. (12) Thus most endemic North American ruminants did not evolve horns because, at the critical combination of body size and diet seen in the evolution of horns in the Old World ruminants, the dispersal of the food resources within the vegetation was too great for an effective home range to be maintained as an exclusive territory. (13) Attention is drawn to the dangers of constructing evolutionary stories about living animals without primary reference to the fossil record to see if the hypotheses are upheld, and of assuming that fossil animal communities can be made to fit models of existing communities.     

Evolutionary systematics and biogeography of the arid habitat‐adapted rodent genus Gerbillus (Rodentia,Muridae): a mostly Plio‐Pleistocene African history

The systematics of the arid‐adapted Old World Gerbillus rodent genus has always been challenging, with many different taxonomic arrangements proposed. Beyond such taxonomic aspects, the timing and geographical pattern of the evolutionary history of this group remains largely unknown. Based on mitochondrial (cytochrome b) and nuclear (interphotoreceptor retinoid‐binding protein) sequences obtained from the specimens of 21 species, we conducted a phylogenetic analysis of the group, estimated the ages and putative ancestral ranges of its major lineages. Four major clades were clearly retrieved within Gerbillus, for which we propose a subgenus rank. We showed that the emergence of the genus dates back to the end of the Miocene, which corresponds to a period of aridification and C4 vegetation expansion in open habitats, while the four sublineages originated at the end of the Pliocene. Most subsequent diversification events occurred during the Pleistocene, a period characterized by recurrent climatic/environmental shifts with increasing aridification during the last two millions of years. Finally, we suggested that most of the Gerbillus evolutionary history took place in Africa. Only in a few instances did dispersal events from Africa to Asia give birth to extant Asian lineages, a pattern that contrasts with what has been found in many animal groups.     

Earliest colobine skeletons from Nakali,Kenya

Old World monkeys represent one of the most successful adaptive radiations of modern primates, but a sparse fossil record has limited our knowledge about the early evolution of this clade. We report the discovery of two partial skeletons of an early colobine monkey (Microcolobus) from the Nakali Formation (9.8–9.9 Ma) in Kenya that share postcranial synapomorphies with extant colobines in relation to arboreality such as mediolaterally wide distal humeral joint, globular humeral capitulum, distinctly angled zona conoidea, reduced medial trochlear keel, long medial epicondyle with weak retroflexion, narrow and tall olecranon, posteriorly dislocated fovea on the radial head, low projection of the femoral greater trochanter, wide talar head with a greater rotation, and proximodistally short cuboid and ectocuneiform. Microcolobus in Nakali clearly differs from the stem cercopithecoid Victoriapithecus regarding these features, as Victoriapithecus is postcranially similar to extant small‐sized terrestrial cercopithecines. However, degeneration of the thumb, a hallmark of modern colobines, is not observed, suggesting that this was a late event in colobine evolution. This discovery contradicts the prevailing hypothesis that the forest invasion by cercopithecids first occurred in the Plio‐Pleistocene, and shows that this event occurred by the late Miocene at a time when ape diversity declined. Am J Phys Anthropol 143:365‐382, 2010. © 2010 Wiley‐Liss, Inc.     

Uniformity of colour vision in Old World monkeys

It is often assumed that all Old World monkeys share the same trichromatic colour vision, but the evidence in support of this conclusion is sparse as only a small fraction of all Old World monkey species have been tested. To address this issue, spectral sensitivity functions were measured in animals from eight species of Old World monkey (five cercopithecine species and three colobine species) using a non-invasive electrophysiological technique. Each of the 25 animals examined had spectrally well-separated middle- and long-wavelength cone pigments. Cone pigments maximally sensitive to short wavelengths were also detected, implying the presence of trichromatic colour vision. Direct comparisons of the spectral sensitivity functions of Old World monkeys suggest there are no significant variations in the spectral positions of the cone pigments underlying the trichromatic colour vision of Old World monkeys.     

Primate evolution of the alpha-globin gene cluster and its Alu-like repeats

The arrangement of alpha-globin genes in Old World and New World monkeys and a prosimian, galago, has been determined by restriction mapping. Recombinant DNAs containing galago and Old World monkey alpha-globin genes have been isolated and subjected to a partial sequence determination for comparison to alpha-globin genes in human, chimpanzee and non-primate mammals. The results of this extensive structural analysis are relevant to several topics concerning the evolution of primate alpha-globin genes and Alu family repeats. All orders of higher primates (i.e. Old and New World monkeys, chimpanzee and human) have the same arrangement of alpha-globin genes. In contrast, the arrangement and correction of galago alpha-globin genes differ from those of higher primates, but are similar to those of non-primate mammals. The 5' and 3'-flanking regions of the human alpha 1 gene are orthologous to the corresponding region in galago, identifying the human alpha 2 gene as the more recently duplicated gene. The human psi alpha 1 gene is found to be inactivated after divergence of the human and galago lineages but prior to the divergence of human and monkey. Orthologous Alu family members in human and monkey DNAs indicate that the dispersion of some Alu repeats occurred prior to the divergence of these lineages. However, the Alu-like repeats of prosimian and higher primates result from entirely independent events giving rise to different repeat elements inserted at distinct genomic positions.     

Coevolution of Tooth Crown Height and Diet in Oreodonts (Merycoidodontidae, Artiodactyla) Examined with Phylogenetically Independent Contrasts

The evolution of increased tooth crown height is considered to be an adaptation for coping with excessive rates of dental wear associated with abrasive herbivorous diets, such as grazing and(or high levels of exogenous grit (e.g. dust, sand, ash). Evolutionary trends in the crown heights of North American ungulates are grossly consistent with a transition from closed forests in the early Eocene to open grasslands in the late Miocene. However, the evolutionary proliferation of hypsodonty (high crowned teeth) in the early and middle Miocene occurs later than the apparent origin of open grassland habitats in North America. The paleoecology of species from the interval between the appearance of grasslands and the evolutionary proliferation of hypsodonty is critical to understanding the role of Cenozoic climate change in mammalian evolution. The paleodiets of late Eocene to middle Miocene oreodonts (Merycoidodontidae) were reconstructed by examining the relative facet development of molars (mesowear). A two-phase diet trend was discovered. Phase 1 suggests either an average reduction in the amount of exogenous grit from the late Eocene to early Oligocene or a decrease in fruit consumption related to the disappearance of more wooded habitats. Phase 2 is a gradual transition from early Oligocene low-abrasion browsing to high abrasion diets similar to mixed feeding and grazing in the Miocene. According to mesowear data, oreodont diets similar to those of modern grazers in terms of abrasion are not seen until the early Miocene (early Hemingfordian land mammal age). The coevolutionary relationship of molar crown height and diet, as represented by mesowear, was examined using phylogenetically independent contrasts. No significant coevolutionary relationship was found. In several instances, diet was found to shift over time despite morphological stasis (i.e. within a single species). These results do not clearly indicate that the overall trend of increasing dietary abrasion imposed sufficient selection to drive crown height evolution in oreodonts. Therefore, direct fossil evidence of dietary abrasion as a causal factor in the evolution of crown height, at least in this clade, is elusive.     

Evolution of the pseudoautosomal boundary in Old World monkeys and great apes

Mammalian sex chromosomes are divided into sex-specific and pseudoautosomal regions. Sequences in the pseudoautosomal region recombine between the sex chromosomes; the sex-specific sequences normally do not. The interface between sex-specific and pseudoautosomal sequences is the pseudoautosomal boundary. The boundary is the centromeric limit to recombination in the pseudoautosomal region. In man, an Alu repeat element is found inserted at the boundary on the Y chromosome. In the evolutionary comparison conducted here, the Alu repeat element is found at the Y boundary in great apes, but it is not found there in two Old World monkeys. During the evolution of the Old World monkey and great ape lineages, homology between the sex chromosomes was maintained by recombination in the sequences telomeric to the Alu insertion site. The Alu repeat element did not create the present-day boundary; instead, it inserted at the preexisting boundary after the Old World monkey and great ape lineages diverged.     

A test of the karyotypic fissioning theory of primate evolution

Karyotypic fissioning theory has been put forward by a number of researchers as a possible driving force of mammalian evolution. Most recently, Giusto and Margulis (BioSystems, 13 (1981) 267–302) hypothesized that karyotypic fissioning best explains the evolution of Old World monkeys, apes, and humans. According to their hypothesis, hominoid karyotypes were derived from the monkey chromosome complement by just such such a fissioning event. That hypothesis is tested here by comparing the G-banded chromosomes of humans and great apes with eight species of Old World monkeys. Five submetacentric chromosomes between apes and monkeys have identical banding patterns and nine chromosomes share the same pericentric inversion. Such extensive karyological similarities are not in accodance with, or predicted by karyotypic fissioning. Apparently, karyotypic fissioning is an extremely uneconomical model of chromosomal evolution. The strong conservation of banding patterns sometimes involving the retention of identical chromosomes indicates that ancient linkages of genes have probably been maintained through many speciation events.     

Corticotropin-releasing hormone-binding protein in primates

In humans, placental corticotropin-releasing hormone (CRH) production has been linked to the determination of gestational length, and a late gestational fall in CRH-binding protein (CRH-BP) has been linked to the onset of parturition. Expression of placental CRH mRNA is limited to primates, and only in man has a circulating CRH-BP been described. As the fall in CRH-BP in late gestation has been associated with parturition in humans, we sought to determine whether a CRH-BP circulated in the plasma of other primates. It is unclear whether maternal plasma CRH concentrations are elevated in New World monkeys and prosimians. We have therefore performed CRH plasma measurements in the blood of pregnant marmosets, in several species of lemur, and in pregnant and fetal rhesus monkeys as a positive control. Using gel chromatography, CRH-BP was detected in the human, gorilla, chimpanzee, orangutan, gibbon, macaque, squirrel monkey, and marmoset, but was absent in the mandrill, spider monkey, and lemur. CRH was detected in the plasma of pregnant marmosets and rhesus monkeys. CRH was also detected in the fetal rhesus monkey, but at lower concentrations than in maternal plasma. CRH immunoreactivity was not detectable in the plasma of pregnant lemurs or in extracts of lemur placenta. In conclusion, a circulating binding protein for CRH exists in all species of apes but occurs variably among New World and Old World monkeys and is absent in lemurs. The variable occurrence of the CRH-BP does not support a role for this protein in the mechanism of parturition in primates. Maternal CRH is elevated in the pregnant marmoset and rhesus, and may play a role in the pregnancy of New and Old World monkeys.     

Adrenal 11-hydroxylase activity in a hypercortisolemic New World primate: adaptive intra-adrenal changes

The squirrel monkey, a representative New World primate, has high plasma cortisol and aldosterone concentrations when compared to Old World primates. We measured adrenal mitochondrial 11-hydroxylase (11-OHase) activity in squirrel monkeys and in two representative Old World species (cynomolgus and rhesus macaques) in an effort to explain these elevated plasma glucocorticoid and mineralocorticoid levels. The activity of 11-OHase was 5-fold higher in the squirrel monkey than in the Old World species tested. Calculated 11-OHase Vmax was different in the squirrel monkey and the cynomolgus. However, the Km values were similar in the New World primate when compared to cynomolgus. The ability of metyrapone to block 11-OHase was less in the former than in the latter. The data are consistent with the hypothesis that the squirrel monkey adrenal cortex possesses an increased number of 11-hydroxylase enzyme units compared to that of Old World primate species, and is therefore more efficient in producing cortisol. This difference in 11-OHase activity in the squirrel monkey, in addition to other previously reported adrenal steroidogenic enzyme alterations, may be adaptive in nature, favoring increased cortisol and aldosterone production in this and possibly other New World primate species.     

Paleoenvironmental basis of cognitive evolution in great apes

A bias favoring tree-dominated habitats and ripe-fruit frugivory has persisted in great ape evolution since the early Miocene. This bias is indicated by fossil ape paleoenvironments, molar morphology, dental microwear, the geographic pattern of extinctions, and extant apes' reliance on wooded settings. The ephemeral aspect of high-quality fruit has placed a premium on cognitive and social means of finding and defending food sources, and appears related to great apes' affinity since the Miocene for wooded, fruit-rich environments. These habitats have, however, undergone a severe withdrawal toward the low latitudes of Africa and Southeast Asia since the late Miocene, corresponding to a decline in the diversity of great apes beginning 9.5 million years ago. Plio-Pleistocene records imply that wooded settings of Africa and SE Asia were prone to substantial fragmentation and coalescence. Once apes were confined to equatorial settings, therefore, habitat instability heightened the spatial/temporal uncertainty of ripe-fruit sources. Prolonged learning, the assignment of attributes to distant places, mental representation, and reliance on fallback foods were all favored in this dynamic environmental context. These abilities helped sustain forest frugivory in most lineages. Fluid social grouping afforded the animals opportunities to locate ephemeral foods in continuous and fragmented forests. Fission-fusion grouping also magnified the problems of object impermanence (of individuals) and dispersion manifested by food sources in the ecological realm. Thus the spatial and temporal dynamics of fruit and wooded habitats since the Miocene are reflected in important components of great ape cognition, foraging, and sociality. In contrast to great apes, cercopithecoid monkeys have increased their plant dietary options and diversified in seasonal environments since the late Miocene. Early hominins eventually severed the habitat bias that characterized the evolution of great apes, and later expanded into diverse environments.     

Structure and evolution of the U2 small nuclear RNA multigene family in primates: gene amplification under natural selection?

The organization of U2 genes was compared in apes, Old World monkeys, and the prosimian galago. In humans and all apes (gibbon, orangutan, gorilla, and chimpanzee), the U2 genes were organized as a tandem repeat of a 6-kb element; however, the restriction maps of the 6-kb elements in these divergent species differed slightly, demonstrating that mechanisms must exist for maintaining sequence homogeneity within this tandem array. In Old World monkeys, the U2 genes were organized as a tandem repeat of an 11-kb element; the restriction maps of the 11-kb elements in baboon and two closely related macaques, bonnet and rhesus monkeys, also differed slightly, confirming that efficient sequence homogenization is an intrinsic property of the U2 tandem array. Interestingly, the 11-kb monkey repeat unit differed from the 6-kb hominid repeat unit by a 5-kb block of monkey-specific sequence. Finally, we found that the U2 genes of the prosimian galago were dispersed rather than tandemly repeated, suggesting that the hominid and Old World monkey U2 tandem arrays resulted from independent amplifications of a common ancestral U2 gene. Alternatively, the 5-kb monkey-specific sequence could have been inserted into the 6-kb array or deleted from the 11-kb array soon after divergence of the hominid and Old World monkey lineages.     

Victoriapithecus: The key to Old World monkey and catarrhine origins

The past ten years have witnessed major changes in reconstructions of the history of Old World monkeys, most of them driven by new material of the Miocene monkey Victoriapithecus from Maboko Island, Kenya. Before the mid-1980s, predictions about the morphological and ecological adaptations of the earliest cercopithecoids relied heavily on evidence from extant colobine and cercopithecine monkeys. It was argued that the earliest cercopithecoids were largely or at least partly folivorous, had short colobine-like faces, and were arboreal. The only studies suggesting that some of these arguments were not true were based on limited knowledge of the anatomy of Victoriapithecus. The presence of semi-terrestrial adaptations in middle Miocene monkeys hinted to some that early monkeys may not have been arboreal. Others attempted to cope with the discrepancy between neontological predictions and the fossil evidence by proposing that limb bones with stronger terrestrial adaptations within the Maboko sample were derived cercopithecine remains, while those with more arboreal features belonged in the subfamily Colobinae and should be regarded as primitive.