Abstract
Associations between fluctuating asymmetry (FA, a putative marker of developmental instability, DI) and life history traits have received a great deal of attention in the non-human literature. However, the patterns found are very heterogeneous and generalizations are difficult to make. In humans, only a few studies have related FA to life histories and fitness. In this paper we study such relationships using hand FA and several key life history traits in 209 post-menopausal Finnish women born between 1946 and 1958. Asymmetry measurements were based on scans of the hands and the life histories of these women were collected using questionnaires. No significant associations were detected and trends were opposite to expectations. We did find evidence for directional asymmetry, as traits in the right hand were larger on average. This may be due to handedness, questioning the usefulness of hand FA as a measure of DI. We conclude that future studies in humans should carefully examine the usefulness of traits as measures of DI.
Highlights
Fluctuating asymmetry (i.e., FA, small random deviations from perfect bilateral symmetry), is assumed to result from developmental instability (i.e., DI, the inability of an individual to buffer its development against directionally random perturbations) [1]
Life-history variables recorded for the purposes of the current study were body mass index (BMI), number of children born during lifetime, age of first and last reproduction, age at menarche, the proportion of offspring surviving until 18 years old and the proportion of male offspring
Out of 21 traits, 13 showed significant directional asymmetry, where in 11 cases, the right side was larger compared to the left
Summary
Fluctuating asymmetry (i.e., FA, small random deviations from perfect bilateral symmetry), is assumed to result from developmental instability (i.e., DI, the inability of an individual to buffer its development against directionally random perturbations) [1]. Associations between FA and various components of fitness or measures of stress have led to the conclusion that DI could reflect individual genetic quality and may play an important role in sexual and natural selection [1]. The literature is very heterogeneous and we understand little about the nature of this variation among studies [1]. Effect sizes greatly varied among studies and this variation could not be explained by the type of trait or type of stress, health or quality measure [2]. There is a need for further research attempting to understand this heterogeneity and the importance of DI in human evolutionary biology
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