在一項(xiàng)研究了交配和撫養(yǎng)之間可能存在的權(quán)衡關(guān)系的研究中,，科研人員發(fā)現(xiàn),，與其他男性相比，睪丸尺寸較小的男性更有可能參與對(duì)孩子的撫養(yǎng),。一項(xiàng)叫做生命史理論的進(jìn)化論假說(shuō)認(rèn)為,，交配與撫養(yǎng)會(huì)爭(zhēng)奪動(dòng)物用于繁殖而付出的有限的能量。此前的研究已經(jīng)提出,，睪酮的減少可能會(huì)抑制為交配做出的努力,，這可能會(huì)把資源導(dǎo)向?qū)π律鷥旱膿狃B(yǎng)上?？紤]到睪丸體積與精子制造以及睪酮水平有聯(lián)系,，James Rilling及其同事研究了睪丸尺寸和男性參與撫養(yǎng)孩子之間的聯(lián)系。這組作者招募了亞特蘭大及其周邊的70名21歲到43歲的生育有1到2歲子女的父親,，然后使用磁共振成像（MRI）測(cè)量了這些男性的睪丸體積,，并且在這些男性觀看他們自己的孩子、陌生人的孩子或者一名成年陌生人的時(shí)候測(cè)量了大腦參與父母動(dòng)機(jī)的一個(gè)區(qū)域的活動(dòng),。這些男性的伴侶也回答了一個(gè)關(guān)于撫養(yǎng)的問(wèn)卷調(diào)查,，該調(diào)查詢問(wèn)了父親對(duì)諸如帶孩子去醫(yī)院和夜間照料孩子等任務(wù)的參與情況。這組作者報(bào)告說(shuō),，父親的睪丸尺寸與他們觀看自己孩子的照片時(shí)觸發(fā)的與撫養(yǎng)有關(guān)的大腦活動(dòng)存在著負(fù)相關(guān)的聯(lián)系,。尤其是對(duì)子女的有表情的面部做出更大反應(yīng)的父親傾向于有較小的睪丸，并且會(huì)更多地參與新生兒護(hù)理,。這組作者說(shuō),，睪丸尺寸與撫養(yǎng)相關(guān)大腦活動(dòng)之間的這種聯(lián)系提示了在交配和撫養(yǎng)之間的一種權(quán)衡的關(guān)系。（生物谷 Bioon.com）
生物谷推薦的英文摘要
PNAS doi: 10.1073/pnas.1305579110
Testicular volume is inversely correlated with nurturing-related brain activity in human fathers
Jennifer S. Mascaro, Patrick D. Hackett, and James K. Rilling
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.
