Figure 2. Dominance rank predicts relative epigenetic age in male baboons.
High rank is associated with elevated values of Δage (β = −0.0785, p=7.39×10−4, N = 105). The y-axis shows relative epigenetic age, a measure of epigenetic aging similar to Δage that is based on the sample-specific residuals from the relationship between predicted age and true chronological age. Positive (negative) values correspond to predicted ages that are older (younger) than expected for that chronological age. Dominance rank is measured using ordinal values, such that smaller values indicate higher rank. Dots and error bars represent the means and standard errors, respectively. Gray values above the x-axis indicate sample sizes for each rank.
Figure 2—figure supplement 1. Methylation levels of clock CpG sites across different genomic compartments.
Each circle represents a sample, with chronological age of the animal at time of sampling shown on the x-axis. The y-axis represents the average methylation level for that sample across CpG clock sites that overlap the annotated genomic region shown in the panel label, stratified by sites that increased (denoted ‘hyper’) or decreased (denoted ‘hypo’) methylation levels with age. Number of clock sites overlapping each annotated region is given in each panel title; a clock site can overlap multiple annotated regions and can therefore be represented in more than one plot. Red and blue lines represent best-fit lines for female and male samples, respectively. All best-fit lines are significant (p<1×10−4).
Figure 2—figure supplement 2. The relationship between age and body mass index in the Amboseli baboons.
Chronological age in years at the time of sampling versus body mass index (kilograms/meters2) for males and females in our sample. Two distinct patterns are observable for both sexes: a stage when animals are still growing (prior to ~7–8 years old) and a stage in which animals vary in BMI as adults. BMI in baboons is measured using the distance between the crown of the head and the rump as the ‘height’ measure and so differs in scale from humans, where BMI is calculated using standing height. Dashed gray line at BMI = 41 shows the cut-off for the analysis in which only males with BMI > 41 were retained for modeling Δage.
Figure 2—figure supplement 3. Relative epigenetic age versus chronological age.
Each circle represents a baboon, colored by the animal’s dominance rank at the time of sampling. The y-axis shows relative epigenetic age, a measure of epigenetic aging similar to Δage that is based on the sample-specific residuals from the relationship between predicted age and true chronological age. Positive (negative) values correspond to predicted ages that are older (younger) than expected for that chronological age. Dominance rank is measured using ordinal values, such that smaller values indicate higher rank.
Figure 2—figure supplement 4. Male dominance rank versus chronological age.
Each circle represents a male baboon at the time of sampling. Nearly all males in the top four rank positions are between ages 7 and 12 years (but not all 7–12 year olds are also high ranking: range of rank positions = 1–20), whereas both young and old males tend to be lower ranking. The quadratic curve represents the model with dominance rank as the response variable and age and age2 as the predictor variables. Rank-for-age was defined as the residuals of this model.