Bernard Wood

Background

I am a medically-trained paleoanthropologist.

My personal 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 and behavior? This means improving our ability to distinguish ‘noise’ from ‘signal’ with respect to our attempts to interpret the hominin fossil record. I also have a long-standing interest in challenging interpretations of data that are uncritically accepted as conventional wisdom.

The initial focus of my human evolution-related research was the postcranial skeleton, but events beyond my control (see below) pushed me in the direction of craniodental evidence, which is where most of my fossil-related research has been concentrated. I enjoy, and benefit from, collaboration. For me research is a social activity. Turning research questions over in your mind is a lonely activity. The stage when the questions are still inchoate is often uncomfortable, but you know the solution will only come if you persist, even if that takes weeks, months, and in my case, sometimes years. Ultimately, at that stage, no-one can help you, but refining how those research questions are tackled is something that for me benefits from working with other people. The majority of my publications are with students¾undergraduate and graduate, and with post-doctoral fellows and other like-minded colleagues. I tend to publish with people who share my worldview and prejudices.

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 invaluable exposure to the wide range of disciplines needed to understand how landscapes and biota evolve. It also introduced me to a group of incomparably talented colleagues, and thus to their intellectual descendants, from whom I have learned¾and continue to learn¾a great deal.

Academic Biography

In 1963 I was admitted as an undergraduate to The Middlesex Hospital Medical School, within The University of London, with the intention of becoming an orthopedic surgeon. I particularly enjoyed anatomy, so in 1966-7, between the pre-clinical and clinical parts of the course, I took time away from my medical studies to do an intercalated BSc 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)¹ was my honors BSc research project. Two of my anatomy teachers had a profound influence on my subsequent career: Eldred Walls influenced my teaching and mentoring, and Michael Day (who later became Professor of Anatomy at St Thomas’s Hospital Medical School, also in London) introduced me to paleoanthropology, and it was Michael Day who, via Mary Leakey, arranged for me to be included in Richard Leakey’s initial 1968 expedition to 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 as a Demonstrator in Anatomy at The Middlesex Hospital Medical School. It was my intention to use this position, and a similar position as Lecturer at 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 hominin fossil remains were from the skull and dentition, but for various reasons each of us would have preferred to work on the postcranial fossils. In 1974 Richard brought the three of us together in his room in The Westbury Hotel 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, emerging with three different length matchsticks, telling us that the choice of region and/or topic would be decided by the length of the match we chose. My recollection is that Michael Day drew the longest match, and he chose the postcranial fossils. Alan Walker’s was the next longest, and he chose to focus on demography and pathology. My match was the shortest, so I had no choice but to work on the cranial remains. This task, which involved generating hypotheses about 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’s act of generosity towards a young inexperienced scholar proved to be a major and decisive influence on my career.

In a series of papers co-authored with medical students who were themselves pursuing an intercalated BSc in anatomy, or with graduate students, post-doctoral fellows, or colleagues, I 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 needed to interpret the hominin cranial remains from Koobi Fora.

¹The numbers in parentheses refer to books [1], refereed papers (1), articles {1}, and book reviews <1> in my list of publications.

The monograph on the Koobi Fora craniodental hominin fossils [5] which was 16 years in the making, combined descriptions of fossils with the results of 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, probably highly sexually-dimorphic, species. I also suggested fossils, which until then had been informally classified as ‘early African Homo erectus,’ likely sampled a distinct species, for which the binomial Homo ergaster was available (42, 51). Some of these taxonomic conventions were widely adopted, although in KF4 all 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 hominins (62). Several other cladistic analyses followed, including an examination of monophyly in Paranthropus (68), and it was from these analyses that my interest in the role of homoplasy in hominin evolution developed (see below).

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 together 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 for 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 limbs (178) provided the first unambiguous evidence that gross morphology (as well as molecular evidence) supported a (Pan, Homo) clade. It also shed light on evolution within the Pan clade (222). The collaboration with Diogo resulted in a book that presented the details of our analysis of the characters of the head and neck and the upper limb [13], and along with Diogo, and many other collaborators, we published the results of dissecting the musculature of Gorilla [10], Hylobates[14], Pan troglodytes [15], Pongo [16] and Pan paniscus [19].

Other research interests include exploiting imaging methods to capture information about the internal structure of fossils (54, 60, 64, 74, 98, 155, 162, 166, 170, 173), including information that improves our understanding of the relationships between dental structure and function (160, 187, 190), the evolution and comparative context of tooth macrostructure (internal and external) and microstructure within the hominin clade (162, 166, 170, 208, 245), improving our understanding of evolution within the Paranthropus clade (90, 127, 151,192, 202, 204, 221), identifying adaptive shifts within the hominin clade (171, 180, 219, 228, 231), improving information about comparative collections of great ape skeletons (200), and encouraging more realistic interpretations of the hominin fossil record (218, 220, 233, 249). From 2009 until its publication in 2011, much of my time and effort was focused on developing and editing the Wiley-Blackwell Encyclopedia of Human Evolution [12, 17] and the companion Wiley-Blackwell Dictionary of Human Evolution [18]. At the other end of the length scale was the OUP Very Short introduction to Human Evolution [7, 20].

Many of my more recent (this was updated in 2023) publications are collaborations with old and new colleagues (229, 230, 233, 236, 237, 239, 244, 245, 250, 253), and with past and current graduate students (231, 235, 241, 242, 246, 252). I have also spent time researching, and trying to interest others in, the history of our discipline (234, 240, 243, 248) and I increasingly appreciate being involved in reviews of topics, both within (220) and related to (248, 254), my main research interests. More recently, I have been pre-occupied with making sure we document the contributions of scientists who have made seminal contributions to reducing our ignorance about human evolutionary history before people like me write about them after they have passed {57, 64, 68, 84, 88, 91, 99, 101}.

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. I am also focusing on exploring the history of comparative anatomy and paleoanthropology (234, 240, 243, 248). I am increasingly interested in the epistemology of paleoanthropology, in part because I realize I have been guilty of being unrealistic about what we think we can know about human evolutionary history. For obvious reasons we focus on what we know, without pausing to consider what evidence is missing, and what impact that missing evidence might have on our interpretations. I have especially appreciated the opportunity to work with—and learn from—Richard Smith on these topics (220, 249).

You do not have to be a rocket scientist to be able to recognize later hominins as hominins, and later members of the genus Homo as members of that genus. But how do you go about recognizing taxa at the base of hominin clade, and near the origin of the Homo clade? Paleoanthropologists, including me, have tended to think that the answer will eventually emerge if you find enough of the right kind of fossils, but the human fossil record is always likely to disappoint us {103}. Early hominins were rare on the landscape, which makes answering some types of questions always challenging (233, 239, 241, 245, 247). I am currently enjoying working with David Pilbeam on what lessons paleoanthropologists might be able to learn from the evolution of other groups of mammals, with a focus on what we might learn from researchers who work on cetaceans.

I write too many commentaries and book reviews. My ‘excuse’ is that they give me a chance to reflect on subjects without the burden of having to do so via publications based on hypothesis-driven research. Lead reviews are an especially useful opportunity to review complex topics <112, 114>.

I have come to realize I write because the act and discipline of assembling my thoughts forces me to think about topics in subtly—and sometimes not so subtly—different ways. On several occasions, writing about a topic has caused me to change my mind quite radically. It is always gratifying if this process is helpful to others, but ultimately I write for selfish reasons.

Examples of specific research interests

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 graduate student, Kes Schroer, explored 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 (204, 209). More recently Alexis Uluutku (PhD student) has been thinking about Paranthropus boisei and early Homo paleoecology, and Gordon Gustafson (Masters student) has been thinking about Paranthropus monophyly, in novel ways.

Comparative primate myology: trunk and lower limbs

A previous study showed 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) and Eve Boyle we are extending 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 limbs (222). Daniel Biggs is picking up where we left off.

Primate phylogenetics

We are extending our interest in the evolution of complex character traits from the phenotype to the genotype. Graduate student Jennifer Baker examined 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 allowed her to quantitatively analyze hormone-receptor interaction in ancient proteins and thus better understand the evolutionary changes that have occurred in our lineage (212, 215).

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 (cranium; upper limb girdle and arm; forearm and hand; lower limb girdle and thigh; leg and foot) 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 (SD) 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. I am working with Katherine Balolia on a review of the evidence for 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 is investigating whether dental microstructure carries any taxonomic and phylogenetic signal (246) and Mark Grabowski is working on testing the null hypothesis that the substantial differences in dental morphology between Homo and Paranthropus are due to drift and not selection.