Sexual differentiation of the mammalian nervous system has been studied intensively for over 25 years. Most of what we know, however, comes from work on relatively non-social species in which direct reproduction (i.e., production of offspring) is virtually the only route to reproductive success. In social species, an individual's inclusive fitness may include contributions to the gene pool that are achieved by supporting the reproductive efforts of close relatives; this feature is most evident in eusocial organisms. Here, we review what is known about neuroendocrine mechanisms, sexual differentiation, and effects of social status on the brain and spinal cord in two eusocial mammals: the naked mole-rat and Damaraland mole-rat. These small rodents exhibit the most rigidly organized reproductive hierarchy among mammals, with reproduction suppressed in a majority of individuals. Our findings suggest that eusociality may be associated with a relative lack of sex differences and a reduced influence of gonadal hormones on some functions to which these hormones are usually tightly linked. We also identify neural changes accompanying a change in social and reproductive status, and discuss the implications of our findings for understanding the evolution of sex differences and the neuroendocrinology of reproductive suppression.

中文翻译：

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真社会哺乳动物的神经内分泌学和性别分化

哺乳动物神经系统的性别分化已被深入研究超过 25 年。然而，我们所知道的大部分内容都来自对相对非社会物种的研究，在这些物种中，直接繁殖（即产生后代）实际上是繁殖成功的唯一途径。在社会物种中，个体的包容性适应性可能包括通过支持近亲的繁殖努力而实现的对基因库的贡献；这一特征在真社会生物中最为明显。在这里，我们回顾了已知的关于神经内分泌机制、性别分化以及社会地位对两种真社会哺乳动物的大脑和脊髓的影响：裸鼹鼠和达马拉兰鼹鼠。这些小型啮齿动物表现出哺乳动物中组织最严密的生殖等级，大多数个体的繁殖受到抑制。我们的研究结果表明，社会性可能与性别差异的相对缺乏以及性腺激素对这些激素通常紧密相关的某些功能的影响减弱有关。我们还确定了伴随社会和生殖状态变化的神经变化，并讨论了我们的发现对理解性别差异的演变和生殖抑制的神经内分泌学的影响。