Wibowo Erik, Johnson Thomas W, Wassersug Richard J
Vancouver Prostate Centre, Vancouver Coastal Health, Vancouver, British Columbia, Canada.
Asian J Androl. 2016 May-Jun;18(3):403-8. doi: 10.4103/1008-682X.173937.
From a Darwinian perspective we live to reproduce, but in various situations genetic males elect not to reproduce by choosing medical treatments leading to infertility, impotence, and, in the extreme, emasculation. For many men, infertility can be psychologically distressing. However, for certain genetic males, being infertile may improve their quality of life. Examples include (1) men who seek vasectomy, (2) individuals with Gender Dysphoria (e.g., transwomen, and modern day voluntary eunuchs), (3) most gay men, and (4) men treated for testicular and prostate cancer. Men who desire vasectomy typically have a Darwinian fitness W >1 at the time of their vasectomies; i.e., after they have their desired number of offspring or consider themselves past an age for parenting newborns. In contrast, prostate and testicular cancer patients, along with individuals with extreme Gender Dysphoria, do not necessarily seek to be sterile, but accept it as an unavoidable consequence of the treatment for their condition undertaken for survival (in case of cancer patients) or to achieve a better quality of life (for those with Gender Dysphoria). Most gay men do not father children, but they may play an avuncular role, providing for their siblings' offspring's welfare, thus improving their inclusive fitness through kin selection. In a strictly Darwinian model, the primary motivation for all individuals is to reproduce, but there are many situations for men to remove themselves from the breeding populations because they have achieved a fitness W ≥1, or have stronger medical or psychological needs that preclude remaining fertile.
从达尔文主义的角度来看，我们活着是为了繁衍后代，但在各种情况下，基因男性会选择导致不育、阳痿甚至极端情况下阉割的医学治疗，从而选择不进行繁衍。对许多男性来说，不育可能会在心理上造成困扰。然而，对于某些基因男性来说，不育可能会提高他们的生活质量。例子包括：（1）寻求输精管切除术的男性；（2）患有性别焦虑症的个体（如变性女性和现代的自愿阉人）；（3）大多数男同性恋者；（4）接受睾丸癌和前列腺癌治疗的男性。想要进行输精管切除术的男性在进行手术时，其达尔文适应性W通常大于1；也就是说，在他们拥有了想要的后代数量，或者认为自己已过生育新生儿的年龄之后。相比之下，前列腺癌和睾丸癌患者以及患有极端性别焦虑症的个体，并不一定主动寻求不育，而是将其作为为生存（癌症患者的情况）或提高生活质量（性别焦虑症患者的情况）而接受的治疗所带来的不可避免的后果。大多数男同性恋者没有亲生孩子，但他们可能会扮演叔伯的角色，为其兄弟姐妹的后代提供福利，从而通过亲缘选择提高他们的广义适应性。在严格的达尔文模型中，所有个体的主要动机都是繁衍后代，但对于男性来说，有许多情况会使他们脱离繁殖群体，因为他们已经达到了适应性W≥1，或者有更强烈的医学或心理需求，从而无法保持生育能力。
