Darryl Holman's Research
Out of the paleodemographic work and my related work on human variation in deciduous tooth emergence, I developed an interest in using departures from perfect symmetry as an indicator of stress in living and skeletal populations. Asymmetry has been used in this way for about 50 years, and there are a number of problems that have beset researchers using fluctuating asymmetry (quantified as the distribution of differences between the left and right sides of a bilateral trait). I developed a new method for analyzing biological asymmetries and quantifying the way stresses act on asymmetries and the trait itself. The approach estimates a single latent distribution for an underlying trait that would develop in the absence of developmental noise and perturbations. Additionally, a distribution of developmental noise is found as a signal superimposed on the bilaterally expressed trait. The method should have broad applicability in the biological sciences for investigating developmental stability and effects of endogenous and exogenous insults on all kinds of bilateral traits. The new method overcomes nearly all of the difficulties in the current approach to studying asymmetries, and unifies two previously unconnected ways of studying stress. Preliminary analyses are given in Holman and Jones (2003).
My co-investigator Robert E. Jones and I are also developing a project that will examine the effects of stress (famine, chronic undernutrition and disease) on bilateral deciduous tooth emergence in children.