Claims about declining sperm counts have been controversial for decades. Many past studies have been suggestive but failed to be conclusive because of serious deficiencies in their design or execution. However, a 2017 comprehensive meta-regression analysis of 185 existing studies involving 42,935 men aimed to avoid these problems and reported a 52% decline in sperm concentration and a 59% decline in sperm counts between 1973 and 2011 in men from North America, Europe, Australia, and New Zealand. This book, written by one of the authors of that study, starts by documenting the decline in reproductive capacity among humans and animals. The declines in men's sperm quantity and quality as well as in testosterone levels have been accompanied by changes in the reproductive systems in many animals. Abnormal genitals are observed in a variety of animals ranging from alligators to pumas and frogs. Sharp declines in populations of birds, fish, and insects are well documented. Next, the author reviews the causes of these reproductive anomalies and provides reasonably convincing evidence that endocrine-disrupting chemicals and insecticides, herbicides, and fungicides have become ubiquitous in our environment and are the likely sources of these alarming findings. The book then reviews recent demographic trends in the Western world where below replacement fertility and rapid population aging are threatening the solvencies of pension and health care systems. The author provides little convincing evidence of the importance of reproductive anomalies to fertility declines except to say that they undoubtedly have an impact. Unfortunately, some statements on this issue are highly problematic. For example, “… the number of children you may have is less than half of the number your grandparents could conceive” (p. 14) supposedly links the decline in sperm count to fertility, but is clearly wrong as there is no one-to-one relationship between declines in sperm count and fertility. Even after decades of decline most men still have sperm counts well above the level considered low by WHO. The author's statement “It is also shocking that in some parts of the world, twentysomething women are less fertile than their grandmothers at age 35” (p. 14) ignores the fact that low fertility of women in their 20s in the Western world is almost entirely due to voluntary postponement of childbearing. A concluding section provides practical advice on how to avoid exposure to harmful environmental chemicals. The book is a powerful call to action on a vital issue that receives too little attention from policymakers and the public. The text is written to appeal to a wide audience, but researchers may find this overview with ample references to earlier scientific studies to be useful as an introduction to the topic. —J.B.

几十年来，关于精子数量下降的说法一直存在争议。过去的许多研究都具有启发性，但由于其设计或执行方面存在严重缺陷而未能得出结论。然而，2017 年对涉及 42,935 名男性的 185 项现有研究进行的综合元回归分析旨在避免这些问题，并报告称 1973 年至 2011 年间来自北美、欧洲的男性精子浓度下降 52%，精子数量下降 59%，澳大利亚和新西兰。这本书由该研究的一位作者撰写，首先记录了人类和动物生殖能力的下降。男性精子数量和质量以及睾丸激素水平的下降伴随着许多动物生殖系统的变化。在从短吻鳄到美洲狮和青蛙的各种动物中观察到异常的生殖器。鸟类、鱼类和昆虫的数量急剧下降是有据可查的。接下来，作者回顾了这些生殖异常的原因，并提供了合理令人信服的证据，证明干扰内分泌的化学品和杀虫剂、除草剂和杀菌剂在我们的环境中无处不在，并且可能是这些令人震惊的发现的来源。然后，这本书回顾了西方世界最近的人口趋势，在这些趋势中，低于替代生育率和人口快速老龄化正在威胁养老金和医疗保健系统的偿付能力。作者几乎没有提供令人信服的证据来证明生殖异常对生育率下降的重要性，只是说它们无疑会产生影响。很遗憾，关于这个问题的一些声明很有问题。例如，“……您可能拥有的孩子数量不到您祖父母可以怀孕的数量的一半”（第 14 页）据说将精子数量的下降与生育能力联系起来，但显然是错误的，因为没有一对一- 精子数量下降与生育能力之间的一种关系。即使在经历了几十年的下降之后，大多数男性的精子数量仍然远高于世卫组织认为的低水平。作者的陈述“同样令人震惊的是，在世界的某些地方，20 多岁的女性在 35 岁时的生育能力比她们的祖母还低”（第 14 页）忽略了一个事实，即西方世界 20 多岁的女性生育率低几乎是完全是因为自愿推迟生育。结论部分提供了有关如何避免接触有害环境化学品的实用建议。这本书强烈呼吁就一个政策制定者和公众很少关注的重要问题采取行动。编写该文本是为了吸引广大读者，但研究人员可能会发现此概述包含对早期科学研究的大量参考，可作为对该主题的介绍。—JB