Competing hypotheses maintain that euprimates originated in Africa, the Indian subcontinent, or East Asia, although the earliest unequivocally identified euprimates have been recorded mainly from Europe and North America. Recently we reported the discovery of Teilhardina asiatica from the earliest Eocene of China. This discovery constitutes the oldest unambiguous euprimate from Asia, and represents the most primitive known omomyid. It suggests that European and North American omomyids were probably rooted in Asia, and casts new light on the Asian-origin hypothesis of euprimates. The possibility of finding morphologically more generalized euprimates (or proto-euprimates) in southern China cannot be dismissed.

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We report on the stratigraphy of the ‘Upper Member’ of the middle Eocene Pondaung Formation at Paukkaung area (central Myanmar), with an emphasis on horizons that have yielded primate fossils. Deposits from the Paukkaung area of the Pondaung Formation have yielded many primate fossils at localities Pk1, Pk2, Pk3, and Pk5. The primate-bearing beds of these localities correspond to horizons of almost the same stratigraphic level. This was confirmed by tracking marker tuff and sandstone beds distributed in the Paukkaung area.

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A new species of eosimiid primate, cf. Eosimias paukkaungensis sp. nov., from the latest middle Eocene of Pondaung, central Myanmar is described. The specimen consists of left and right mandibular fragments preserving only the M₃, so that its generic status is provisional. The cf. E. paukkaungensis fossil is much larger than homologues of the two Eosimias species from China. It is too large to be a mandible for the taxa represented by the Eosimias-like calcaneus from Pondaung, but smaller than Bahinia pondaungensis, another eosimiid of the Pondaung fauna. The discovery of cf. E. paukkaungensis indicates diversity of eosimiids in East and Southeast Asia during the middle Eocene.

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Paleogene temporal and paleogeographic constraints on mammalian faunal interchange between Africa and Eurasia are reassessed in order to discuss the origin of Primates, Anthropoidea, and Catarrhini. During the late Paleocene to early Eocene interval, the fossil record indicates faunal exchange between Africa and the North Tethyan areas involving several groups of mammals, such as the earliest primates, carnivores, and some archaic ungulates. The polarities of such dispersal events are unresolved to date. Regarding the paleogeography of anthropoid origins, previous cladistic assessments argued for a dispersal from Asia to Africa during the early Eocene. However, faunal exchange during that period has been documented only between Africa and Europe. A speculative basis for an Asian origin of African zegdoumyid rodents is the only body of evidence that suggests that the earliest anthropoids might have migrated to Africa from Asia. Finally, according to the putative occurrence of catarrhines (amphipithecids) in the middle Eocene of Asia, a middle Eocene migration event towards Africa is proposed, although this is supported only by hystricognath and anomaluroid rodents, and by anthracotheriid artiodactyls. In conclusion, the early paleobiogeographic history of anthropoids remains conjectural because of the lack of phylogenetic resolution.

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Amphipithecidae of late middle Eocene to late Eocene of Myanmar and Thailand is a phylogenetically enigmatic group that some place with Anthropoidea and others with Adapoidea. A linkage with adapoids is hard to demonstrate because it relies largely on a series of similarities that are arguably symplesiomorphies of Primates as a whole. The possibility that amphipithecids are specially related to crown anthropoids (e.g. Aegyptopithecus) is suggested by some shared-derived dental and gnathic anatomy. The postcranial anatomy indicates that the amphipithecids, if they are anthropoids, are probably a distantly related stem group outside the clade of African late Eocene-to-Recent anthropoids. Even the stem-group anthropoid status of amphipithecids is not supported by the absence of postorbital closure and enlarged olfactory bulbs, since postorbital closure and reduced olfactory bulbs characterize a more inclusive crown haplorhine clade of Tarsius plus Anthropoidea. An appealing possibility is that amphipithecids are basal haplorhines whose divergence would have predated the Tarsius–Anthropoidea split. Larger amphipithecids equal or exceed the body size of the largest known Eocene primates. Dental and mandibular anatomy suggests these large-bodied amphipithecids were fruit and hard-object (nut) feeders. A more primitive contemporary amphipithecid, Myanmarpithecus, was smaller, about 1–2 kg, and its cheek teeth suggest a frugivorous diet but do not imply seed eating. The humerus and calcaneus of a large amphipithecid from Myanmar (Pondaungia or Amphipithecus) suggest a slow-moving arboreal quadrupedal locomotion like that of lorises. A talus of an amphipithcid is more suggestive of an active arboreal quadruped.

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Catarrhines originated in Afro-Arabia during the Paleogene, and were restricted to this zoogeographic province until the early Miocene. During this period of isolation, several major clades of catarrhines originated. The pliopithecoids were the first catarrhines to migrate out of Africa at ~18–20 Ma, while contemporary proconsulids and dendropithecids may have been restricted to Afro-Arabia. Hominoids and Old World monkeys originated in Africa prior to 20 Ma, but neither clade became an important component of the catarrhine fauna until the middle to late Miocene. At ~15–17 Ma, hominoids expanded into Eurasia, while cercopithecids arrived somewhat later, during the late Miocene. The earliest catarrhines in Eurasia, Dionysopithecus and Platodontopithecus from Sihong in China (~17–18 Ma), represent the primitive sister group of all other pliopithecoids. From this ancestral stock in Asia, the more specialized pliopithecines extended their range westwards into Europe by ~16–17 Ma, where a pliopithecine-like common ancestor gave rise to the crouzeliines. The only known crouzeliine from Asia, Laccopithecus, from the late Miocene of China, points to a late arrival of this clade in the region. Small catarrhines from the middle Miocene of Pakistan (~16–17 Ma), and new material from China, may possibly have closer ties with dendropithecids, proconsulids, or hylobatids.

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Sivapithecus and Dryopithecus are well-described Miocene hominids (great apes and humans), both known since the 19th century. Over the years these genera have been combined into one (Dryopithecus) or separated up to the subfamily level. Each have been dismissed as interesting side branches, hailed as direct ancestors, or recognized as sister clades to one or more clade of extant hominid. Here I argue that they are each stem taxa of the two living hominid clades Ponginae and Homininae. A famous poem by Rudyard Kipling tells the tale of a British and Afghan soldier whose differences (in ethnicity) obscure their similarities (in character). The relationship between Sivapithecus and Dryopithecus is similar. On the one hand, Sivapithecus is restricted to South Asia, has thickly enameled molars, robust jaws, and superficially baboon-like forelimbs; Dryopithecus is European, has thinly enameled molars and gracile jaws, with suspensory forelimbs. On the other hand, both are great apes, both had suspensory adaptations, large brains, and delayed development, and both are closely related to living hominids. Recognition of the likely relations of Sivapithecus and Dryopithecus provides insight into the causes, timing, and paleobiogeography of crown hominid origins.

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We report here a new fossil hominoid tooth from the Late Miocene (~7.8 Ma) of the Hari-Talyangar region, India. The large-sized hominoid M² is rather bunodont and its occlusal morphology and size are fairly distinctive from both the Sivapithecus sivalensis and Sivapithecus indicus conditions. Correlation between upper and lower molar breadth in extant hominoids and Sivapithecus species suggests that this upper molar fits within an estimated range of Indopithecus (= ‘Gigantopithecus’) M² variation; a lower M₂ of the same taxon is known from the same region. However, molar size and morphology are also consistent with a S. parvada attribution. Therefore its formal taxonomic allocation remains problematic. Sivapithecus was primarily a fruit eater and its teeth do not generally show caries, but the present molar exhibits a large caries, indicating a probable diet of grasses and fruits. The supposed diet of the new fossil tooth suggests that these Late Miocene apes of the Hari-Talyangar region lived in a habitat drier than that of Sivapithecus. A review based on the present fossil and palaeoecological and palaeoclimatological evidence supports a hypothesis that the Siwalik fossil apes disappeared by the Late Miocene because of a decrease in humidity and an increase in seasonality, aridity, and unpredictable climatic conditions brought about by the intensification of the monsoon system, eventually leading to expansion of grasslands at the expense of rainforests.

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The relationship between the Yuanmou hominoid and the Lufeng hominoid (Lufengpithecus lufengensis), both from Yunnan Province, China, and among the most abundantly represented fossil hominoid of Eurasia, has been the subject of much debate. In the past 10 years, comparative studies of cranial and dental morphology of the Lufeng and Yuanmou hominoids indicate that the two hominoids resemble each other more than either of them resemble any other Miocene hominoid. In this paper, we summarize the dental differences seen between the Yuanmou and Lufeng hominoids, and discuss their implications. Our results show that the Lufeng hominoid has relatively smaller front teeth, smaller M¹, and higher SQ than the Yuanmou hominoid, indicating a more folivorous or soft diet, such as leaves and berries, in the former. Tooth wear analysis indicates that both upper and lower molars of the Yuanmou hominoid were more heavily worn than those of the Lufeng hominoid, offering additional support to the findings of tooth size proportion and shearing crest development. We propose that different diets might have characterized the two hominoid populations, the differences possibly related to the environment, behavior pattern, and population structure of the Yuanmou and Lufeng hominoids.

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Late Miocene large-bodied hominoids from Yunnan, China are critical to the understanding of hominid and hominoid origins and evolution in Asia. The aim of the present study is to examine dental development and ontogeny of Lufengpithecus from Yuanmou and Lufeng. Based on scanning electron microscope observations of enamel incremental markings, the mean crown formation time of Lufengpithecus incisors was estimated to be 3.7–4.6 years, which is longer than that of Proconsul, Paranthropus, and early Homo, and closer to that of Australopithecus afarensis, Pan, and Homo sapiens. The dental eruption characteristics of Lufengpithecus lufengensis, including age at first molar emergence, eruption sequence of dentition, and M₁/I₁ eruption pattern, show an ape-like, not human-like, developmental pattern. High and regular frequency of linear enamel hypoplasia indicates that late Miocene L. lufengensis suffered from regular physiological stress associated with seasonal dietary fluctuations.

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The Thai-Japanese Paleontological Expedition Team (TJPET) has been conducting paleontological and geological fieldwork in Thailand for a number of years. In January 2000, an upper molar (CMu6-1’00) of a large-bodied Miocene hominoid was found by TJPET in a lignite mine in the Chiang Muan basin, northern Thailand. It was the first record of a Miocene hominoid from a Southeast Asian country. Two years later, TJPET found a second hominoid specimen (CMu15-5’01) in the same lignite mine. The second specimen was collected from the Upper Lignite Member, while the first one had come from the Lower Lignite Member. The age of Chiang Muan is estimated to be at around the boundary of the Middle/Late Miocene (ca. 10–12 Ma) based on mammalian fauna and paleomagnetic study. There may be several hundred thousand years temporal difference between the Upper and Lower Lignite Members. Chaimanee et al. (2003) reported more hominoid specimens from the same site, and created a new species, cf. Lufengpithecus chiangmuanensis. The taxonomic status of the Chiang Muan hominoids, however, is still a matter of debate. Nevertheless, the discovery of Miocene hominoids from Chiang Muan has revealed the potential of Thailand for understanding hominoid evolution in Southeast Asia.

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One of the major lacunae in our knowledge of African hominoid evolution concerns the origins of the chimpanzee and gorilla. Several thousand specimens from the Plio–Pleistocene of Africa have been attributed to Hominidae (sensu stricto) of which only a few, including Ardipithecus ramidus, have been re-interpreted by some authors as possibly representing an ape rather than a hominid (Senut, 1998). Four recently discovered ape-like specimens from the late Middle Miocene (12.5 Ma) and Late Miocene (5.9 Ma) of Kenya partly fill the gap in the fossil record of African apes, and show some morphological and metric affinities with teeth of chimpanzees and gorillas. If these few specimens from Kenya are indeed more closely related to chimps and gorillas than to hominids, then this implies that the dichotomy between African apes and hominids occurred several million years earlier than is currently estimated by most researchers. Furthermore these ape teeth from Ngorora and Lukeino suggest that extant African apes evolved in Africa, and did not immigrate into the continent from Europe or Asia.

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In the Eocene, distribution of the order Primates in the northern part of eastern Eurasia was confined to Mongolia. A form of Omomyidae (Altanius orlovi) is represented. Northern Eurasian primates attributed to later times cover the interval between the Late Miocene (Late Turolian) to the Middle Pleistocene (Mindel–Riss). Primates are distributed in the western part of eastern Eurasia (Moldavia, Ukraine), Transcaucasus (Georgia, Iranian Azerbaijan) and Central Asia (Tadjikistan, Afghanistan, Transbaikalian, Mongolia). The total number of known primate taxa is not large: seven genera and eleven species in three families (Omomyidae, Hominidae, Cercopithecidae). The Neogene and Pleistocene representatives of the order Primates comprise either widely distributed Eurasian forms or endemic taxa. The distribution pattern of primates in the western and eastern part of eastern Eurasia can be interpreted in relation to links with African and East Asian faunal provinces. By the Late Pleistocene all non-human representatives of the order Primates in the northern part of eastern Eurasia became extinct.

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Primates evolved in the tropical forests of the Late Paleocene or Early Eocene. The cognitive, locomotor and life-history characteristics that define primates evolved under the equable and generally non-seasonal conditions that distinguish such forests. All primates since have carried the biological imprint of this original association with tropical forests. In Asia, the persistence of tropical forests in Indonesia from the Eocene onward has permitted tarsiers to endure and evolve, while other Eocene primates became extinct on their home continents. Following a disastrous decline in tropical forest distribution and primate diversity at the Late Eocene/Oligocene boundary, forests and primates rebounded during the Late Oligocene and Miocene. The dominant Old World primates of most of the Neogene were hominoids, which inhabited large tracts of woodlands and forests throughout Africa and Eurasia. These relatively large, frugivorous animals were quadrupedal, but many were capable of undertaking bridging postures that allowed them to stretch between arboreal substrates. Hominoids reached the apex of their evolutionary success in the Middle Miocene, then declined—as a result of the slow disappearance of their forest homes—in the Late Miocene, especially after 10 Ma. The extirpation of apes at this time can be traced to their inability to live in more seasonal and open habitats. Old World monkeys originated in forest biomes, but became the dominant primate of the late Neogene because of their ability to live in environments ranging from closed, non-seasonal rainforests to open savannahs and alpine meadows. This adaptability can be traced to their slightly faster life histories and their ability to thrive on a wide range of both high- and low-quality foods.

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In 1991, a partial cranium of a fossil colobine monkey was found in Kanagawa Prefecture, Japan. Its geological age is Late Pliocene (ca. 2.5 Ma). It is larger than skulls of living colobine monkeys and resembles a male example of Pliocene Dolichopithecus ruscinensis from France. However, the cranium exhibits some distinctive features, notably very thin postorbital rims (lateral margins of the orbit). Therefore, a new subgeneric and specific name Dolichopithecus (Kanagawapithecus) leptopostorbitalis is given.

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