**Figure 2.** **Trends of fatty-acid composition with increasing life span.** In each panel, data points with error bars indicate means ± standard errors, of GC-MS quantitations for the indicated lipid component expressed as a percent of total fatty acids quantified for that run. *X*-axes display **1.0** [N2DRM, SR803, SR818, SR819, SR820; *n* = 20], **1.1 - 1.2** [SR800, SR801; *n* = 4], **1.6** [SR807; *n* = 5], **2.3** [SR806; *n* = 3] and **9.6** [SR808; *n* = 4]. Medians (**A**, **B** and **E**) the percent of total fatty acids in each indicated class; (**C**) Average Chain Length; (**D**) activities of fatty-acid elongases, inferred from FA ratios (C16:0/C14:0, C18:0/C16:0); (**F**) Peroxidation Index (defined in **G**) activities of ω-3 desaturases, inferred from FA ratios (e.g., C20:4(n-3)/C20:3(n-6)), and ω-3/ω-6 ratios for all PUFAs; and (**H**) inferred Δ9 desaturase activities (C16:1Δ9/C16:0, C18:1Δ9/C18:0). In each panel, *R* denotes the Pearson correlation coefficient, reflecting a linear relationship between the log_{(10)} of strain lifespan and the indicated fatty-acid parameter. *R _{S}* is the Spearman correlation coefficient, relating the rank-order of strain lifespan to rank-order of fatty-acid parameter per class (e.g., the % of total FAs) in 36 assays.