Relatively clean snow and ice in the Indus River Basin during the COVID-19 pandemic may have reduced meltwater in 2020, compared with the 20-year average.
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Edited by Michael S. Gazzaniga, University of California, Santa Barbara, CA, and approved August 2, 2013 (received for review March 25, 2013)
Significance
Life History Theory posits a trade-off between mating and parenting effort, which may explain some of the observed variance in human fathers’ parenting behavior. The current study tested this hypothesis by measuring aspects of reproductive biology related to mating effort, as well as paternal nurturing behavior and the brain activity related to it. Both testosterone levels and testes volume were negatively correlated with paternal caregiving. In response to viewing pictures of one’s own child, brain activity in a key component of the reward and motivation system predicted paternal caregiving and was negatively related to testes volume. These results suggest that the biology of human males reflects a trade-off between mating effort and parenting effort.
Abstract
Despite the well-documented benefits afforded the children of invested fathers in modern Western societies, some fathers choose not to invest in their children. Why do some men make this choice? Life History Theory offers an explanation for variation in parental investment by positing a trade-off between mating and parenting effort, which may explain some of the observed variance in human fathers’ parenting behavior. We tested this hypothesis by measuring aspects of reproductive biology related to mating effort, as well as paternal nurturing behavior and the brain activity related to it. Both plasma testosterone levels and testes volume were independently inversely correlated with paternal caregiving. In response to viewing pictures of one’s own child, activity in the ventral tegmental area—a key component of the mesolimbic dopamine reward and motivation system—predicted paternal caregiving and was negatively related to testes volume. Our results suggest that the biology of human males reflects a trade-off between mating effort and parenting effort, as indexed by testicular size and nurturing-related brain function, respectively.
Footnotes
- ↵1To whom correspondence should be addressed. E-mail: jrillin{at}emory.edu.
Author contributions: J.S.M. and J.K.R. designed research; J.S.M. and P.D.H. performed research; J.S.M., P.D.H., and J.K.R. analyzed data; and J.S.M. and J.K.R. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1305579110/-/DCSupplemental.
Testicular volume predicts paternal brain activity
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- Evolution
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