The internal cranial anatomy of the Middle Pleistocene Broken Hill 1 cranium

08 Dec 2017

The cranium (Broken Hill 1 or BH1) from the site previously known as Broken Hill, Northern Rhodesia (now Kabwe, Zambia) is one of the best preserved hominin fossils from the mid-Pleistocene. Its distinctive combination of anatomical features, however, makes its taxonomic attribution ambiguous. High resolution microCT, which has not previously been employed for gross morphological studies of this important specimen, allows a precise description of the internal anatomical features of BH1, including the distribution of cranial vault thickness and its 2 internal composition, paranasal pneumatisation, pneumatisation of the temporal bone and endocranial anatomy. Relative to other chronologically and taxonomically relevant specimens, BH1 shows unusually marked paranasal pneumatisation and a fairly thick cranial vault. For many of the features analysed, this fossil does not exhibit the apomorphic conditions observed in either Neandertals or Homo sapiens. Its morphology and the general shape of the brain and of the skull may be partly explained by an allometric relationship relative to the features observed in Homo erectus s.l. However, further research is still necessary to better appreciate the cranial anatomy of BH1 and the role of Homo rhodesiensis/Homo heidelbergensis in the course of human evolution. This paper also deals with more general aspects of scientific practices in palaeoanthropology. In particular, we give precise descriptions of many internal anatomical features of Broken Hill 1, a specimen discovered in 1921. This important and unique dataset will allow independent comparative studies in the future. However, we were limited in our study by the very restricted amount of comparative information available for Homo fossils. In our view, scientific papers dealing with the anatomical description of hominin specimens, both in the case of announcements of new discoveries and of discussions of important specimens found decades ago, should always include qualitative and quantitative data that truly allow for further independent research.