Research Interests:

My interests include systematics, evolutionary anatomy, morphometrics, and paleoanthropology. My research focuses on the genus Homo, and I have been able to study fossils from many of the important prehistoric localities in Africa, western Eurasia, Java, and China. I am particularly interested in the early evolution of Homo in Africa, species-level diversity within the genus, the first dispersals of populations into Asia, and the paleobiology of Homo erectus. Using comparative anatomical and metric evidence, I am also attempting to map the evolutionary relationships among human populations of the Middle Pleistocene. I find this work in paleoanthropology to be highly rewarding. Discoveries of fossils call for constant adjustments to our thinking about the evolutionary process, and the future promises to bring many exciting new developments.

One of my current research projects involves Dmanisi in Georgia. Since 2001, I have worked frequently at the Georgian National Museum in Tbilisi, and at the site itself. Our international team has uncovered complete hominin skulls, vertebrae, ribs, clavicles, a fragmentary scapula, bones of the upper and lower limbs, and foot parts. A number of the specimens are in excellent condition, and at least five individuals are represented. This material has been excavated from sedimentary layers that are ca. 1.77 million years old. The Dmanisi fossils constitute perhaps the most important assemblage of early Homo on record from any Plio-Pleistocene locality. In contrast to the situation at many other sites, where the remains are scattered through a substantial thickness of deposits, the Dmanisi hominins may be regarded as close contemporaries and representative of a single population. Here there is a unique opportunity to study anatomical variation within an ancient group. Such assessments help to identify traits that vary between individuals (including characters that are sexually dimorphic) and traits that are relatively stable. The latter are more useful in species recognition and diagnosis.

Questions about the taxonomic utility of characters, and species recognition, are central to investigations of evolutionary history. I approach these questions within the context provided by H. erectus and Middle Pleistocene hominins. The morphology of H. erectus can be documented from more than 30 partial or complete crania from localities in the Far East, western Asia, and Africa. While there is regional variation, the skulls have relatively small capacities, large basicranial platforms, low vaults that are maximally broad at the level of the supramastoid crests, strongly flexed occipitals, and projecting faces. This geographically dispersed paleospecies must be ancestral to populations evolving later in the Middle Pleistocene. For the Middle Pleistocene hominins, endocranial volume is about 280 cm³ greater than the norm for H. erectus. Additional characters claimed to distinguish mid-Pleistocene assemblage(s) include increased vertical height of the braincase, a broader frontal, and rounding of the parietal vault and occiput. The occipital upper scale exceeds the nuchal plane in length. Slight differences in browridge shape have been cited as useful taxonomically. On the strength of such changes, the mid-Pleistocene hominins have been allocated to one or more species distinct from H. erectus, the Neanderthals, and modern humans. This taxonomy is based on the assumption that characters of the vault and face are developmentally independent, rather than a reflection of encephalization occurring within the H. erectus lineage. However, the mechanism(s) underlying such structural adjustments, and particularly the role of the expanding brain, have remained poorly understood. My work is designed to clarify the interactions of brain volume, the cranial base, vault proportions, and the face within archaic and more recent groups. With this information it is possible to assess the taxonomic valence of individual characters. An improved understanding of character variation is critical to recognizing and diagnosing species lineages within the presently confusing array of later Pleistocene fossils.

Recent publications:

Rightmire, G.P., Ponce de León, M.S., Lordkipanidze, D., Margvelashvili, A., Zollikofer, C.P.E.,

2017. Skull 5 from Dmanisi: descriptive anatomy, comparative studies, and evolutionary significance. Journal of Human Evolution, 104: 50-79.

Rightmire, G.P., 2017. Middle Pleistocene Homo crania from Broken Hill and Petralona: morphology, metric comparisons, and evolutionary relationships. In: Human Paleontology and Prehistory: Contributions in Honor of Yoel Rak. A. Marom and E. Hovers, eds. Springer, Heidelberg, pp. 145-159.

Zollikofer, C.P.E., Ponce de León, M.S., Margvelashvili, A., Rightmire, G.P., Lordkipanidze, D., 2014. Response to comment on “A complete skull from Dmanisi, Georgia, and the evolutionary biology of early Homo.” Science, 344: 362-363.

Rightmire, G.P., 2013. Homo erectus and Middle Pleistocene hominins: brain size, skull form, and species recognition. Journal of Human Evolution, 65: 223-252.