Do attachment styles represent early environmental calibration, or do they reflect heritable individual differences, as suggested by some research (Bailey, Kirk, Zhu, Dunne, & Martin, 2000; Goldsmith & Harman, 1994)? Are individual differences in attachment stable over the life course? Do the underlying psychological mechanisms of attachment coordinate with the specific features of adaptive problems posed by each alternative strategy? These questions await further conceptual and empirical work. Nonetheless, studies demonstrate that early age of menarche is indeed linked with parental marital unhappiness and more rejection from the father, as well as with an earlier age of dating men. This suggests promise for the theory of early attachment in promoting different adult sexual strategies (Kim, Smith, & Palermiti, 1997), although it is not inconsistent with a pure heritability interpretation (see Ellis, 2005, for a discussion). Recent empirical work also supports the theory that a low quality childhood environment, especially one marked by an absent father, a psychologically dysfunctional father, and family disruption, does indeed predict an early age of menarche, which can lead to early onset of sexual activity and a short-term mating strategy (Neberich, Penke, Lehnart, & Asendorpf, 2010; Tither & Ellis, 2008).