Table 2.

Results for an ‘extended’ animal model of female age at first birth (AFB) in Swiss women (n = 6435), in which genetic effects via the husband are estimated. This model differs from animal model 1 (table 1) only in introducing the genetic effect of the spouse (and the genetic covariance with the direct genetic effect). Birth year is mean-centred. Parish cohort is defined as the parish-specific decade in which the individual was born. Family terms represent the natal nuclear families of the focal individual or her husband. Total additive genetic variance is calculated following Bijma [19]. The effect estimates are the point estimates ± standard error. Fixed and random effects were tested via z scores or χ² scores, respectively.

	effect estimate	estimate relative to VP	z/χ2	p
fixed effects
birth year	−9.2 × 10−3 ± 1.8 × 10−3	—	−5.13	<0.001
(birth year)2	−4.3 × 10−6 ± 1.3 × 10−5	—	−0.33	0.740
random effects
wife's parish cohort	1.1 ± 0.2	0.045 ± 0.009	90.6	<0.001
wife's family	1.5 ± 0.5	0.064 ± 0.021	25.1	<0.001
husband's family	1.1 ± 0.4	0.045 ± 0.018	15.3	<0.001
additive genetic (wife)	2.4 ± 0.7	0.102 ± 0.029	51.9	<0.001
additive genetic (husband)	1.3 ± 0.4	0.052 ± 0.017	57.7	<0.001
residual	16.7 ± 0.8	0.693 ± 0.035	—	—
natal environmental covariance / correlation	1.2 ± 0.4 / 0.91 ± 0.39		13.6	<0.001
additive genetic covariance / correlation	1.2 ± 0.4 / 0.68 ± 0.30		31.6	<0.001
total additive genetic variance	6.1 ± 1.1	0.253 ± 0.046	59.7	<0.001