About the Authors

Birgitte Hollegaard

Contributed equally to this work with: Birgitte Hollegaard, Sean G. Byars

Affiliation Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark

Sean G. Byars

Contributed equally to this work with: Birgitte Hollegaard, Sean G. Byars

Affiliation Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark

Jacob Lykke

Affiliation Department of Obstetrics and Gynaecology, Roskilde Hospital, Roskilde, Denmark

Jacobus J. Boomsma

JJBoomsma@bio.ku.dk

Affiliation Centre for Social Evolution, Department of Biology, University of Copenhagen, Copenhagen, Denmark

Competing Interests

The authors have declared that no competing interests exist.

Author Contributions

Helped plan and organize research: JL. Conceived and designed the experiments: JB BH SB. Performed the experiments: SB BH. Analyzed the data: BH SB. Wrote the paper: JB BH SB.