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.
虽然被父亲投资的孩子在现代西方社会有充分的优势证明，很多父亲选择不投资他们的孩子，为什么有些男人做这样的选择？生命历史理论对这种差异化的父母投资提供了一个解释通过假设交配和养育子女的努力之间的一种平衡, 这也许能解释一些观察到的人类父亲养育子女行为的差异。 我们通过测量和交配努力相关的生育生物学， 父母培育行为和与交配努力相关的大脑活动这几个方面来检验了这种假设。 血浆睾丸酮水平和睾丸大小都是与父亲独立照顾负相关的。 作为看自己的孩子的照片的反应， 腹部侧面区域的活动－一种中脑边缘多巴胺奖励和鼓励系统的关键组成部分－预测了父母养育是和睾丸大小负相关的。 我们的结果表明了人类男性的生物学反映了交配努力和养育努力之间的平衡， 分别通过睾丸尺寸和养育相关的大脑功能来记录。