Maternal malnutrition during gestation and lactation is known to have adverse effects on offspring. We evaluate the impact of maternal diet on offspring bony labyrinth morphology. The bony labyrinth develops early and is thought to be stable to protect vital sensory organs within. For these reasons, bony labyrinth morphology has been used extensively to assess locomotion, hearing function, and phylogeny in primates and numerous other taxa. While variation related to these parameters has been documented, there is still a component of intraspecific variation that is unexplained. Although the labyrinthine developmental window is small, it may provide the opportunity for developmental instability to produce corresponding shape differences, as measured by fluctuating asymmetry (FA). We hypothesized that (a) offspring with poor maternal diet would exhibit increased FA, but (b) no unilateral shape difference. To test these hypotheses, we used two groups of rats (Rattus norvegicus; Crl:WI[Han] strain), one control group and one group exposed to a isocaloric, proteinrestricted maternal diet during gestation and suckling. Individuals were sampled at weaning, sexual maturity, and old age. A Procrustes analysis of variance identified statistically significant FA in all diet-age subgroups. No differences in level of FA were identified among the subgroups, rejecting our first hypothesis. A principal components analysis identified no unilateral shape differences, supporting our second hypothesis. These results indicate that bony labyrinth morphology is remarkably stable and likely protected from a poor maternal

Objectives: Intraspecific shape variation in the recent Homo sapiens bony labyrinth has been assessed for association with sexual dimorphism, body size, and genetic differences, but has not been fully assessed for association with extrinsic factors, such as subsistence strategy and climate. While the skull overall is known to vary with these variables, the bony labyrinth develops in utero and exhibits microstructural stability through adulthood. Therefore, labyrinthine morphology may be resistant to extrinsic variables. Materials and methods:We collected labyrinthine shape data using computed tomography from 262 individuals associated with archeological or contemporary collections used for dissection in North America, Europe, Africa, and Southeast Asia. We assessed the data for observer error and asymmetry. Shape variation is examined between subsistence strategy groups and climate type groups with Principal Components Analyses and Procrustes ANOVA's, and shape variation was correlated with specific climate data (precipitation, temperature, altitude) with a two-block partial least squares analysis.Results: Both inter-and intra-observer error as well as asymmetry minimally affected labyrinthine shape variation. We found that both subsistence strategy and climate each account for a statistically significant 7% of overall shape variation, and that specific climate variables have statistically significant correlation with labyrinthine shape variation (RV 0.52527).Discussion: Morphological variation in this sample indicates that the labyrinth is not entirely resistant to extrinsic factors associated with subsistence strategy and climate. Shape differences are not localized to specific regions of the labyrinth, but may contribute to the complicated variation seen in recent human evolution and warrants further exploration.