Abstract:
Cortical bone and dentine share similarities in their embryological origin, development,
and genetic background. Few analyses have combined the study of cortical bone and dentine to quantify
their covariation relative to endogenous and exogenous factors. However, knowing how these tissues relate
in individuals is of great importance to decipher the factors acting on their evolution, and ultimately to
understand the mechanisms responsible for the different patterns of tissue proportions shown in hominins.
The aims of this study are to examine age-, sex-, and ancestry-related variation in cortical bone and dentine
volumes, and to preliminary assess the possible covariation between these tissues in modern humans and in
five composite Neandertals. The modern analytical sample includes 12 immature individuals from France
and 49 adults from France and South Africa. Three-dimensional tissue proportions were assessed from
microtomographic records of radii and permanent maxillary canines. Results suggest ontogenic differences
and a strong sexual dimorphism in cortical bone and dentine developments. The developmental pattern
of dentine also seems to vary according to individual’s ancestry. We measure a stronger covariation signal
between cortical bone and dentine volumes than with any other dental tissue. A more complex covariation
pattern is shown when splitting the modern sample by age, sex, and ancestry, as no signal is found in
some subsamples while others show a covariation between cortical bone and either crown or radicular
dentine. Finally, no difference in cortical bone volume is noticed between the modern young adults and
the five young adult composite Neandertals from Marine Isotopic Stages (MIS) 5 and 3. Greater dentine volumes are measured in the MIS 5 chimeric Neandertals whereas a strong interpopulation variation in
dentine thickness is noticed in the MIS 3 chimeric Neandertals. Further research on the cortical bonedentine
covariation will increase understanding of the impact of endogenous and exogenous factors on the
development of the mineralized tissues.
