Bernard A. Wood
Professor of Human Origins
|Address:||800 22nd St NW
Washington, District Of Columbia 20052
Areas of Expertise
I am a medically trained paleoanthropologist.
My research interests are all related in one way or another to a long-standing pre-occupation with hominin systematics. How can we improve our ability to recognize species in the fossil record, and how can we do a better job of reconstructing their phylogenetic relationships?
The initial focus of my research was the postcranial skeleton, but events beyond my control (see biography) pushed me in the direction of cranio-dental evidence and that is where most of my recent fossil-related research has been concentrated. I enjoy collaborating so the majority of my publications are with students, undergraduate and graduate, post-doctoral fellows and with other colleagues.
At the beginning of my career I was fortunate that Richard Leakey gave me the opportunity to be involved with research at what was then East Rudolf, now Koobi Fora, in northern Kenya. My main contribution was the analysis of the fossil hominin cranial remains, but the opportunity to be part of the broader East Rudolf Research Project provided me with an invaluable exposure to the wide a range of disciplines that are needed to understand how landscapes and biota evolve. It also introduced me to a group of incomparably talented colleagues from whom I have learned, and in some cases continue to learn, a great deal.
My current research interests are phylogeny reconstruction, hominin systematics, dental evolution, evolvability within the hominin clade, and diet reconstruction; some individual projects are confined to one of these interests, others span several.
Comparative models for mandibular premolar molarization
One of the most compelling lines of evidence for Paranthropus monophyly is that both Paranthropus boisei and Paranthropus robustus have molarized mandibular premolars. Under the monophyly hypothesis this would be considered a shared-derived feature, and if instead the two taxa were paraphyletic, then mandibular premolar molarization would be a homoplasy. Mandibular premolar molarization is unusual in Old World primates, but it occurs quite commonly in callitrichids. A former graduate student, Kes Schroer, is exploring the context in which this occurs in these New World primates, to test the hypothesis that molarization of the mandibular premolars is a synapomorphy of Paranthropus.
Comparative primate myology: trunk and lower limb
A previous study has shown that the comparative gross morphology of the muscles of the head, neck, thorax and upper limb is consistent with the pattern of relationships supported by molecular evidence among higher primates and among 17 major primate clades. It is also the case that while some of the derived features shared among the great apes involve the evolution of independent muscles, others involve the loss, or simplification, of the musculature. In collaboration with Rui Diogo (Howard University) we will extend this study to the trunk and lower limb to test the null hypothesis that gross muscle morphology in those regions is also consistent with the relationships among the great apes supported by the majority of molecular evidence and that similar examples of loss, or simplification, are seen in the lower limb.
We are extending our interest in the evolution of complex character traits from the phenotype to the genotype. Graduate student Jennifer Baker is working with Derek Wildman to examine the genotypic evolution of complex character traits. She is focusing on the molecular evolution of a superfamily of transcription factors, the Nuclear Hormone Receptors (NR), a class of proteins with a strong history of successful protocols for functional analysis on ancient proteins. The evolutionary relationships of the superfamily of NRs are well known, but the biochemical, structural, and functional consequences of molecular evolution in the primate lineage remain unclear. Ancestral sequence reconstruction will allow us to quantitatively analyze hormone-receptor interaction in ancient proteins and thus better understand the evolutionary changes that have occurred in our lineage.
Regional comparisons of the efficacy of hard and soft tissue evidence for phylogeny construction
We will compare the phylogenetic valence of the hard-tissue morphology of the major regions of the body with the phylogenetic valency of the gross morphology of the musculature of the same regions to test the hypothesis that the superior performance of the latter is a global rather than a regional phenomenon.
Regional patterns of sexual dimorphism: exploring the use of the phylogenetic bracket to predict regional patterns of sexual dimorphism in the hominin clade
Sexual dimorphism is an important source of intra-specific variation, but no study has explored the regional differences in the degree and pattern of sexual dimorphism across the skeleton of higher primates. If there is any consistency in the SD seen in the African ape clade, then the principle of the phylogenetic bracket can be used to predict the primitive condition of the degree and pattern of sexual dimorphism in the hominin clade.
Paranthropus monophyly: a comparative mammalian context
To what extent do other mammalian groups in East and southern Africa show examples of regional sister taxa. We are reviewing the evidence within other mammalian clades of sound evidence of sister taxa in the two regions.
Evolutionary trends in hominin gnathic and dental evolution
Are there constraints on the evolvability of dental and gnathic morphology within the hominin clade? To what extent is selection responsible for the patterns of evolution we observe within the hominin clade? Chrisandra Kufeldt, a graduate student, is investigating whether dental microstructure carries any phylogenetic signal, and Mark Grabowski is working on testing the hypothesis that the substantial differences in dental morphology between Homo and Paranthropus are due to selection.
In 1963 I was admitted as an undergraduate to The Middlesex Hospital Medical School, The University of London, with the intention of training to become an orthopedic surgeon. I particularly enjoyed anatomy and in 1966-7, between the pre-clinical and clinical parts of the course, I took time off and was awarded an honors BSc degree in anatomy. The degree program included John Napier’s primatology course and a human evolution course taught by Michael Day. My first publication, a multivariate analysis of the OH 8 talus (1) (N.B., all numbers refer to refereed papers, etc. in the bibliography), was my honors BSc research project. Two of my anatomy teachers had a profound influence on my subsequent career; Eldred Walls, the Professor, shaped me as a teacher, and Michael Day (who later became Professor of Anatomy at St Thomas’s Hospital Medical School, also in London) introduced me to paleoanthropology. It was Michael Day who, via Mary Leakey, arranged for me to be included in Richard Leakey’s initial 1968 expedition to what was then called East Rudolf.
In 1970 I graduated in medicine and surgery from The University of London and after briefly practicing as a clinician I was appointed Lecturer in Anatomy at The Middlesex Hospital Medical School. It was my intention to use this post, and a similar one at the The Charing Cross Hospital Medical School, to study for the first part of the Fellowship of the Royal College of Surgeons.
However, my plans for a surgical career were put on hold in 1972 when I was invited by Richard Leakey to become a member of what later became known as the Koobi Fora Research Project. I was one of three anatomists (Michael Day and Alan Walker were the others) charged with describing the hominin fossils recovered from East Rudolf. The majority of the fossil remains were from the skull and dentition, but for various reasons the three of us would each have preferred to work on the postcranial fossils. Richard Leakey brought us together in his hotel room in New York to try to resolve this impasse, but we all stuck to our guns. Not a little frustrated, Richard went into the bathroom then emerged having broken three matches into different lengths. He told us that the choice of region and/or topic would be decided by the length of the match he then invited us to draw. Mine was the shortest match, so I had no choice but to work on the cranial remains. This task, which involved determining how many taxa were represented among the hominin cranial fossils, led to my interest in patterns of intra- versus interspecific variation. Thus the topic of my PhD (The University of London, 1975) was sexual dimorphism in the skeleton of higher primates (14). Richard Leakey’s act of generosity towards a young scholar proved to be a major influence on my career.
A series of papers co-authored with medical students who were themselves pursuing a BSc in anatomy, graduate students, post-doctoral fellows, or colleagues, examined variation in primates and fossil hominins with respect to the role of allometry in generating shape differences (18, 26), intra- vs. inter-specific variation (75), relative tooth size (23, 25), relative tooth cusp proportions (38, 39, 61, 89), enamel morphology (54, 60), tooth root morphology (64, 66), tooth crown development (31), mandibular size and shape (47), and basicranial anatomy (29, 36, 43). All of these projects were part of the comparative anatomical context I used to interpret the hominin cranial remains from Koobi Fora. The monograph on the Koobi Fora craniodental hominin fossils (Wood, 1991), which was 16 years in the making, combined descriptions of fossils with the results of statistical analyses undertaken to test alpha taxonomic and phylogenetic hypotheses. The results suggested that fossils attributed to Homo habilis probably represent two species, Homo habilis sensu stricto and Homo rudolfensis (79, 82). In contrast, the substantial size and shape variation among the fossils assigned to Paranthropus boisei was consistent with their belonging to a single, highly sexually dimorphic, species. I also suggested that the fossils that until then had been informally classified as “early African Homo erectus” could represent a distinct species, for which the binomial Homo ergaster was available (42, 51). Some of these taxonomic conventions were widely adopted, although they were presented as hypotheses that needed to be tested using additional data and analyses.
My involvement in the analysis of the fossil hominins from Koobi Fora continued to influence my choice of research topics. Once it became apparent that more than one lineage was being sampled at Koobi Fora, Andrew Chamberlain and I published a cladistic analysis of early hominin phylogeny (62). Several other cladistic analyses followed, including an examination of monophyly in Paranthropus (68), and thus began an interest in the role of homoplasy in hominin evolution.
Following the publication of the Koobi Fora monograph, my work on hominin variation and diversity continued (81), but my research began to embrace broader themes in hominin paleobiology, including the faunal context of hominin evolution (83, 84), biogeography (115), relative size (91, 105), life history (92, 157), evolutionary ecology (94, 136), systematics (112, 116, 127, 147, 150, 177), and tempo and mode within the hominin clade (90). It was at this time that I began a long-term research program dedicated to assessing the efficacy of anatomical traits for recovering reliable phylogenetic information. Mark Collard took on this topic for his graduate research and we questioned the ability of craniodental traits to recover reliable phylogenetic information in extant hominoids and cercopithecoids (118). Subsequent work with Sally Gibbs and Mark Collard showed that soft tissues seemed to be more effective than fossilized hard tissues at recovering phylogeny (121). This led to a productive collaboration with Rui Diogo to systematically collect data about gross muscle morphology. Our initial study of the musculature of the head, neck, thorax and upper limb (178) provided the first unambiguous evidence that gross morphology (as well as molecular evidence) supported a Pan, Homo clade.
Other research interests include improving our understanding of the relationships between dental structure and function (160, 187), the evolution and comparative context of tooth macrostructure (internal and external) and microstructure within the hominin clade (162, 166, 170), and identifying adaptive shifts within the hominin clade (171, 180). Recently, most of my time and effort has been focused on developing and editing the Wiley-Blackwell Encyclopedia of Human Evolution and the companion Wiley-Blackwell Student Dictionary of Human Evolution.