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The Primate Fossil Record

Posted on: Sunday, 28 September 2003, 06:00 CDT

Hartwig, W. C. (ed.). 2002. THE PRIMATE FOSSIL RECORD. Cambridge University Press, Cambridge, United Kingdom, 530 + xiv pp. ISBN 0- 521-66315-6, price (cloth), $175.00.

This valuable new volume challenges significant components of the normal view of primate history. In Chapter 1, the editor briefly comments that ". . . fossil primates have always been interpreted in light of how they might relate to living ones. Whether this tendency stems from scientific insight or myopia, a framework of closely related forms and conservative phylogenies has persevered." In the normal view (e.g., Clark 1959; Eisenberg 1981; Fleagle 1999), the earliest primates were Plesiadapiformes (or were closely related to them) that "took to the trees" at the end of the Cretaceous. The suborder Prosimii emerged in the Eocene, and ancestral Anthropoidea diverged in the Late Eocene in Africa. Derived African anthropoids of the Oligocene that retained only 2 premolars founded our infraorder Catarrhini. The superfamily Hominoidea radiated in East Africa and Eurasia beginning in the early Miocene, but by the Pliocene, specialized Cercopithecoidea (Old World monkeys) had replaced most hominoids. A bipedal African hominoid begat the family Hominidae during climatic perturbations of the Plio-Pleistocene.

Fieldwork and analysis by the contributors to this book over the last 2 decades have revised several key points of this view, but the editor (Chapter 1) makes it clear that the volume is not a new synthesis of fossil and living primate systematics. Instead, multiple systematic inferences coexist, supported by conflicting interpretations of the same evidence. Following the brief introduction, Rasmussen reviews current functional models for the origin of the primates by reprising his observations of Caluromys derbianus to address 2 competing hypotheses, that primates were initially successful "visual predators" (Cartmill 1972) and that primates initially exploited fruits at terminal branches of evolving angiosperms (Sussman 1991). Well-chosen authors with few or no axes to grind introduce 4 of the 5 sections that follow: the earliest primates and fossil prosimians (Covert); the origin and diversification of anthropoid primates (Dagosto); the fossil record of early catarrhines and Old World monkeys (no introduction); the fossil record of hominoid primates (Pilbeam); and the fossil record of human ancestry (McHenry). Each chapter reviews discovery, interpretation, and debate about a set of fossils (thoroughly illustrated with photographs and drawings), and discusses the evolutionary history of the taxon. Authors explain the phylogenetic inferences leading to their taxonomies, which seldom agree exactly when they overlap. Chapters conclude with lists of selected key historical references by fossil genus. The book ends with a comprehensive list of references cited, an index of historical figures, and a taxonomic index. Citations cover literature through 1998 comprehensively. The volume includes stimulating chapters treating all fossil primates, but this review outlines only a few modifications of the traditional primate history illuminated by agreement and disagreement among some contributors.

What new information about the origins of primates do fossils reveal?-Plesiadapiformes are quickly dropped from the primates (Rasmussen, p. 7; Covert, p. 13), although specimens obtained since this book went to press have revealed intriguing shared characters with early primates (Bloch et al. 2001). Covert's overview and the following chapters on Adapiformes (Gebo, Chapter 4) and Tarsiiformes (Gunnell and Rose, Chapter 5) illustrate differing inferences about early primates. A cladistically correct classification divides primates into the suborders Strepsirhini and Haplorhini (Pocock 1918); in contrast, the traditional division is gradistic (e.g., prosimians versus anthropoids) but is confounded by numerous taxa that share derived characters with both groups (e.g., Tarsius, many Malagasy "prosimians"). Gebo (Chapter 3) stresses the cladistic association of Eocene-Early Oligocene Adapiformes with living strepsirhine Lemuriformes, whereas Gunnell and Rose (Chapter 4) place Tarsiiformes with Lemuriformes and Adapiformes in the suborder Prosimii. One Middle Eocene specimen, Tarsius eocaenus (Middle Eocene), however, is the most ancient fossil assigned to a living genus of primates. If molar form and detailed cranial similarity cited by Gunnell and Rose confirm affinity of Tarsius and Omomyoidea, and if molecular and other characters ally Tarsius with anthropoid primates, Gebo wins the argument that Eocene Tarsiiformes belong with us in the suborder Haplorhini, and haplorhine ancestry starts in the Eocene.

What new information about the origins of the hyporder Anthropoidea do fossils reveal?-Beard (Chapter 9) points out that only recently consensus was that the origin of Anthropoidea (Platyrhini + Catarrhini) was near the Eocene-Oligocene boundary in Africa (p. 146). In contrast, fossils constituting the new family Eosimiidae arguably show very early differentiation of Anthropoidea from their sister group (Tarsiiformes) in Asia. Parsimony analysis (Ross et al. 1998) supports Beard's cladistic inferences, and recent mitochondrial DNA analysis (Arnason et al. 2002) strongly supports a pre-Cenozoic origin of primates and pre-Cenozoic divergence of Haplorhini and Strepsirhini, allowing for very early separation of Anthropoidea from Tarsiiformes, in agreement with the fossils.

What is new about the systematics of humans?-There is little disagreement about the taxonomic level separating Hominoidea from its sister clade, Cercopithecoidea. The earliest cercopithecoid, Victoriapithecus maccinnesi, comes from the East African Miocene and shares the special, derived bilophodont molar structure with living Cercopithecoidea (Benefit and McCrossin, Chapter 16). Unspecialized catarrhines coexisted with Victoriapithecus in East Africa and radiated in Eurasia (Harrison, Chapter 19). Traditionally, they have been lumped in Hominoidea, and Proconsul of East Africa has been called "the earliest hominoid," since its discovery in 1933. Pilbeam (Chapter 18) implies this view of the Miocene Hominoidea, although he hedges his bets in his opening reference to ". . . hominoids (or at least non-cercopithecoid catarrhines that might be cladistically hominoids).. . ."

Pliopithecus was the first fossil primate assigned to Hominoidea, but Begun (Chapter 15) places Pliopithecus and its possible Eurasian Miocene relatives in Pliopithecoidea as an extinct primitive catarrhine phylum. Harrison (Chapter 19) assigns Proconsul and other early Miocene Catarrhini of "Afro-Arabia" to 2 additional extinct superfamilies, the Proconsuloidea and Dendropithecoidea. Morotopithecus of East Africa is the earliest Miocene fossil left in Hominoidea based on the derived state of 1 lumbar vertebra.

The new view of descent of hominoids may make biogeographic sense, with several extinct Eurasian clades of catarrhines evolving independently of African catarrhines until Africa and Asia connected in the Middle Miocene. Hominoidea then radiated in Europe (Begun, Chapter 20), Asia (Kelly, Chapter 21), and Africa (Ward and Duren, Chapter 22). The authors agree that most Miocene Hominoidea belong to 1 family, Hominiciae, and that an Asian clade survived by living Pongo and an African sister clade survived by living Gorilla, Pan, and Homo had separated by the middle to late Miocene.

Assigning most Hominoidea to the family Hominidae and living African apes and humans to the subfamily Homininae (Kelly) or tribe Hominini (Begun) probably makes sense to general mammalogists, who may be disappointed that authors specializing in "hominids" (McHenry, White, Dunsworth and Walker, and F. Smith) maintain the traditional segregation of bipedal Plio-Pleistocene Hominoidea into the family Hominidae. White recognizes 2 genera of "earliest hominids" and describes and discusses Ardipithecus and 7 paleospecies of the genus Australopithecus. Dunsworth and Walker choose a simple classification of the proliferation of genera and species of ancient "Homo," sticking to the series H. habilis, H. rudolfensis, and H. erectus for the period from 2.3 to 0.3 x 10^sup 6^ years. F. Smith adopts a bushier view including 2 genera (Paranthropus and Australopithecus) for White's "Australopithecus," and species designations for many fossils grouped under H. erectus by Dunsworth and Walker.

There is no summation of the book. Hartwig is true to his introduction and leaves us to ponder alternative views unsupervised. The multiple views of phylogeny of the same fossils in one volume may inspire discussion and debate and encourage students to think for themselves about conclusions rather than accept one view of the record or any of its parts. Consequently, The Primate Fossil Record could be the centerpiece of an excellent graduate seminar on the history and practice of systematics and paleontology (if not for its high price, which would strain my students' budgets). Critical comparison with the monographic reviews of Conroy (1990) and Le Gros Clark (1959) would round out such a seminar nicely. Those wishing to catch up on their genealogies back to the Cretaceous or to ponder stimulating examples of divergent reasoning and conclusions from the same evidence will find the book an exc\ellent resource.-PETER S. RODMAN, Department of Anthropology, University of California, Davix, CA 95616, USA.

LITERATURE CITED

ARNASON, U., ET AL. 2002. Mammalian mitogenomic relationships and the root of the eutherian tree. Proceedings of the National Academy of Sciences 99:8151-8156.

BLOCH, J. I., D. M. BOYER, AND P. D. GINGERICH. 2001. Positional behavior of Late Paleocene Carpolestes simpsoni (Mammalia, ?Primates). Journal of Vertebrate Paleontology 21, supplement 3:34a.

CARTMILL, M. 1972. Arboreal adaptations and the origin of the order Primates. Pp. 97-122 in The functional and evolutionary biology of primates (R. Tuttle, ed.). Aldine, Chicago, Illinois.

CONROY, G. C. 1990. Primate evolution. W. W. Norton, New York.

EISENBERG, J. F. 1981. The mammalian radiations: an analysis of trends in evolution, adaptation, and behavior. University of Chicago Press, Chicago, Illinois.

FLEAGLE, J. G. 1999. Primate adaptation and evolution. Academic Press, New York.

LE GROS CLARK, W. E. 1959. The antecedents of man. Edinburgh University Press, Edinburgh, United Kingdom.

POCOCK, R. I. 1918. On the external characters of lemurs and Tarsius. Proceedings of the Zoological Society of London 55:19-53.

ROSS, C. F., B. WILLIAMS, AND R. F. KAY. 1998. Phylogenetic analysis of primate relationships. Journal of Human Evolution 35:221- 306.

SUSSMAN, R. W. 1991. Primate origins and the evolution of angiosperms. American Journal of Primatology 23:209-223.

Journal of Mammalogy, 84(3):1125-1127, 2003

PETER S. RODMAN, Department of Anthropology, University of California, Davis, CA 95616, USA.

Copyright American Society of Mammalogists Aug 2003

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