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 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. 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.

¹The numbers in parentheses refer to books [1], refereed papers (1), articles {1}, etc. in my list of publications

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 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. 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 Leakey’s act of generosity towards a young inexperienced 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 [5], 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 (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 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 limbs (178) provided the first unambiguous evidence that gross morphology (as well as molecular evidence) supported a Pan, Homo clade, as well as increasing our understanding of evolution with the Pan clade (221). 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 have 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), improving our understanding of evolution within the Paranthropus clade (90, 127, 151,192, 201, 203, 220), identifying adaptive shifts within the hominin clade (171, 180, 218, 227, 230), improving information about comparative collections of great ape skeletons (199), and encouraging more realistic interpretations of the hominin fossil record (217, 219, 232). From 2010 onwards, much of my time and effort has been focused on developing and editing the Wiley-Blackwell Encyclopedia of Human Evolution [12, 17] and the companion Wiley-Blackwell Dictionary of Human Evolution [18].