Investigating associations between developmental integration and physiological stress

Objectives

Integration, or patterns of correlation between structural elements, is of interest in diverse fields. Analysis is, however, generally limited to group-level comparisons. This paper presents a novel combination of methods to quantify developmental integration (i.e., patterns of covariation which arise during growth) so that a univariate score is computed, summarizing individual integration in contrast to group-level trends. This provides a means of investigating factors which influence variation in multi-scale detail.

Materials and Methods

Human ossa coxae from archaeological remains were assessed. After capturing os coxae shape through geometric morphometric methods, patterns of integration between modules—that is, the ilium, ischium and pubis—were summarized via individual scores calculated through a Leave-One-Out (LOO) approach. Osteological assessments allowed integration to be explored in relation to demographic factors and physiological stress experience during development as implied through chronologically matched linear enamel hypoplasia (LEH).

Results

While skeletal sex and site of origin influenced gross os coxae shape, variation in integration appeared to be related to stress experienced during development, with individuals exhibiting matched LEH having significantly lower integration scores.

Discussion

It is possible that developmental stress is associated with decreased integrated skeletal growth and, while gross shape is unaffected, the traces of this disruption can be detected through the method presented here. While analyses implied that this hypothesis must be treated cautiously, it is proposed that quantifications of integration in skeletal materials can potentially be employed to investigate developmental stress experience. Further work is needed to validate these assumptions.