Heritable spouse effects increase evolutionary potential of human reproductive timing

Area of Science:

• Evolutionary biology
• Human reproductive behavior
• Behavioral genetics

Background:

• Sexual reproduction involves complex interactions, particularly in species with pair bonding like humans.
• The role of male traits in reproductive phenotypes and their evolutionary impact is understudied.
• Reproductive timing is often considered a female-specific trait in biological research.

Purpose of the Study:

• To investigate the indirect genetic effects of males on their partners' reproductive timing.
• To determine the evolutionary significance of male genetic contributions to female reproductive phenotypes.
• To re-evaluate the heritable variance and evolutionary potential of reproductive timing in women.

Main Methods:

• Utilized extensive genealogical data from 6435 mothers across four centuries.
• Employed an animal modeling approach to estimate indirect genetic effects.
• Analyzed the relationship between partner genotype and female age at first birth.

Main Results:

• A woman's age at first birth is significantly influenced by her partner's genotype.
• This indirect genetic effect correlates positively with the direct genetic effect in women.
• Total heritable variance in reproductive timing is doubled when partner effects are included.

Conclusions:

• A substantial portion of heritable variation in women's reproductive timing is mediated through partner effects.
• Male genetic contributions play a crucial, previously underestimated role in female reproductive timing.
• The evolutionary potential for reproductive timing is significantly greater than previously assumed.