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Open Access Highly Accessed Research article

Blackmailing: the keystone in the human mating system

Milind G Watve12*, Anuja Damle2, Bratati Ganguly3, Anagha Kale2 and Neelesh Dahanukar1

Author Affiliations

1 Indian Institute of Science Education and Research, Sai Trinity Building, Pashan, Pune 411021, India

2 Anujeeva Biosciences Pvt. Ltd., 10, Pranav Society, 1000/6-c Navi Peth, Pune 411030, India

3 Department of Chemistry and Molecular Biology, North Dakota State University, 1231 Albrecht Avenue, PO Box-5516, Fargo, ND 58105-5516, USA

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BMC Evolutionary Biology 2011, 11:345  doi:10.1186/1471-2148-11-345

Published: 29 November 2011

Abstract

Background

The human mating system is characterized by bi-parental care and faithful monogamy is highly valued in most cultures. Marriage has evolved as a social institution and punishment for extra pair mating (EPM) or adultery is common. However, similar to other species with bi-parental care, both males and females frequently indulge in EPM in secrecy since it confers certain gender specific genetic benefits. Stability of faithful monogamy is therefore a conundrum. We model human mating system using game theory framework to study the effects of factors that can stabilize or destabilize faithful committed monogamy.

Results

Although mate guarding can partly protect the genetic interests, we show that it does not ensure monogamy. Social policing enabled by gossiping is another line of defense against adultery unique to humans. However, social policing has a small but positive cost to an individual and therefore is prone to free riding. We suggest that since exposure of adultery can invite severe punishment, the policing individuals can blackmail opportunistically whenever the circumstances permit. If the maximum probabilistic benefit of blackmailing is greater than the cost of policing, policing becomes a non-altruistic act and stabilizes in the society. We show that this dynamics leads to the coexistence of different strategies in oscillations, with obligate monogamy maintained at a high level. Deletion of blackmailing benefit from the model leads to the complete disappearance of obligate monogamy.

Conclusions

Obligate monogamy can be maintained in the population in spite of the advantages of EPM. Blackmailing, which makes policing a non-altruistic act, is crucial for the maintenance of faithful monogamy. Although biparental care, EPM, mate guarding and punishment are shared by many species, gossiping and blackmailing make the human mating system unique.