Table 1. Model parameters and their specifications.

Parameter	Symbol	Type*	Model	Theoretical Values	Value(s) used	Sensitivity analyses (Online supplement)	Figure
Gompertz coefficient	a	Fixed	All	[0,∞]	0.08	0.00001, 0.0001, 0.001, 0.01, 0.1, 0.2	S21
Heritability	h	Fixed	All	[0,1]	0.95	1, 0.99, 0.95, 0.9, 0.8, 0.5, 0.2	S16
Lag parameter in b function	γ	Fixed	All	[-∞,∞]	-2	-10, -7, -4, -2, -1, 0	S22
SD of baseline PTVs	-	Fixed	All	[0,∞]	0.1	0, 0.01, 0.1, 0.2, 0.5 1, 3	S13
SD of LRS	-	Fixed	All	[0,∞]	0.1 of LRS	0, 0.01, 0.1, 0.2, 0.5 1, 3	S15
Maximum fertility per unit time	fmax	Fixed	All	[0,∞]	1	NA
Individuals per generation	-	Fixed	All	-	10,000	NA
Generations	-	Fixed	All	-	500	10,000	S12
Weight	W	VAS	1	[0,∞]	exp(N(0, 2))	NA
Weight for PTV1	W1	VAS	2,3,4	[0,∞]	exp(N(0, 2))	NA
Weight for PTV2	W2	VAS	2,3,4	[0,∞]	exp(N(0, 2))	NA
Minimum possible aging rate	b0	VAS	All	[0,∞]	[0,1]	NA
Physiological trait value	PTV	Evolving	1	[-∞,∞]	N(0, 0.1) & Eqn (S1)	NA
Physiological trait value #1	PTV1	Evolving	2,3,4	[-∞,∞]	N(0, 0.1) & Eqn (S1)	NA
Physiological trait value #2	PTV2	Evolving	2,3,4	[-∞,∞]	N(0, 0.1) & Eqn (S1)	NA
Gompertz aging rate	b	Evolving	All	[0,∞]	Eqns (3) & (5)	NA
Age at death	Ad	Evolving	All	[0,∞]	see text	NA
Fertility	f	Evolving	All	[0,∞]	Eqns (4) & (6)	NA
Lifetime reproductive success	LRS	Evolving	All	[0,∞]	Eqn (2)	NA

*There are three parameter types: those fixed across all simulations except sensitivity analyses ("Fixed"), those fixed within a given simulation but varying across simulations ("VAS"), and those that evolve across generations within each simulation ("Evolving"). Evolving parameters are tracked and used to assess what happens in a simulation, while VAS parameters are changed to assess model sensitivity to their values.