Table 1.

Descriptive statistics for biomarkers and sexual orientation (SO) measures: Mean (M), SD, sample size (N), and % missing data (% missing) based on the full sample size (N = 827)

Variable	N	M	SD	% missing
Fraternal birth order	600	0.27	0.21	27.44
Handedness	826	0.18	0.24	0.12
Familiality	334	0.05	0.12	59.61
SO self-identification	580	2.77	1.79	29.75
SO attraction	578	2.78	1.74	30.12
SO behavior	562	2.77	1.81	32.04

Note that possible values for each biomarker (fraternal birth order, handedness, and familiality) all range from 0 to 1. Higher FBO values indicate a greater proportion of older brothers, higher handedness values indicate greater non−right-handedness, and higher familiality values indicate a greater proportion of gay/bisexual male family members. Self-identification of SO was coded as follows: 0 = heterosexual, 2 = bisexual/other, and 4 = gay. Attraction and behavior (Likert scale measures of sexual orientation) range from 0 to 4; participants who reported 0 on these scales were classified as heterosexual, whereas participants with values 1 to 4 were grouped together to make the nonheterosexual group. See SI Appendix, Sexual Orientation for comparisons of participants with values of 1, 2, 3, and 4. See SI Appendix, Figs. S1 and S2 for frequency distribution of participants by sexual orientation responses. Data were found to be missing at random (for details, see SI Appendix, Missing Data).