The most widely cited explanation for the evolution of reliable signals is Zahavi's so‐called Handicap Principle, which proposes that signals are honest because they are costly to produce. Here we provide a critical review of the Handicap Principle and its theoretical development. We explain why this idea is erroneous, and how it nevertheless became widely accepted as the leading explanation for honest signalling. In 1975, Zahavi proposed that elaborate secondary sexual characters impose ‘handicaps’ on male survival, not due to inadvertent signalling trade‐offs, but as a mechanism that functions to demonstrate males' genetic quality to potential mates. His handicap hypothesis received many criticisms, and in response, Zahavi clarified his hypothesis and explained that it assumes that signals are wasteful as well as costly, and that they evolve because wastefulness enforces honesty. He proposed that signals evolve under ‘signal selection’, a non‐Darwinian type of selection that favours waste rather than efficiency. He maintained that the handicap hypothesis provides a general principle to explain the evolution of all types of signalling systems, i.e. the Handicap Principle. In 1977, Zahavi proposed a second hypothesis for honest signalling, which received many different labels and interpretations, although it was assumed to be another example of handicap signalling. In 1990, Grafen published models that he claimed vindicated Zahavi's Handicap Principle. His conclusions were widely accepted and the Handicap Principle subsequently became the dominant paradigm for explaining the evolution of honest signalling in the biological and social sciences. Researchers have subsequently focused on testing predications of the Handicap Principle, such as measuring the absolute costs of honest signals (and using energetic and other proximate costs as proxies for fitness), but very few have attempted to test Grafen's models. We show that Grafen's models do not support the handicap hypothesis, although they do support Zahavi's second hypothesis, which proposes that males adjust their investment into the expression of their sexual signals according to their condition and ability to bear the costs (and risks to their survival). Rather than being wasteful over‐investments, honest signals evolve in this scenario because selection favours efficient and optimal investment into signal expression and minimizes signalling costs. This idea is very different from the handicap hypothesis, but it has been widely misinterpreted and equated to the Handicap Principle. Theoretical studies have since shown that signalling costs paid at the equilibrium are neither sufficient nor necessary to maintain signal honesty, and that honesty can evolve through differential benefits, as well as differential costs. There have been increasing criticisms of the Handicap Principle, but they have focused on the limitations of Grafen's model and overlooked the fact that it is not a handicap model. This model is better understood within a Darwinian framework of adaptive signalling trade‐offs, without the added burden and confusing logic of the Handicap Principle. There is no theoretical or empirical support for the Handicap Principle and the time is long overdue to usher this idea into an ‘honorable retirement’.

中文翻译：

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障碍原理：错误的假设如何成为科学原理

对于可靠信号的演变，引用最广泛的解释是 Zahavi 所谓的 Handicap Principle，它提出信号是诚实的，因为它们的生产成本很高。在这里，我们对障碍原则及其理论发展进行了批判性回顾。我们解释了为什么这个想法是错误的，以及它如何被广泛接受为诚实信号的主要解释。1975 年，Zahavi 提出精心设计的第二性征对雄性生存造成“障碍”，这不是由于无意的信号权衡，而是作为一种机制向潜在配偶展示雄性的遗传质量。他的障碍假说受到了许多批评，作为回应，Zahavi 澄清了他的假说并解释说它假设信号既浪费又昂贵，并且它们的发展是因为浪费强制诚实。他提出信号在“信号选择”下进化，这是一种非达尔文主义的选择，有利于浪费而不是效率。他坚持认为障碍假说提供了一个通用原则来解释所有类型的信号系统的演化，即障碍原则。1977 年，Zahavi 提出了诚实信号的第二个假设，它收到了许多不同的标签和解释，尽管它被认为是障碍信号的另一个例子。1990 年，Grafen 发表了他声称证明 Zahavi 的障碍原则正确的模型。他的结论被广泛接受，让分原则随后成为解释生物学和社会科学中诚实信号演化的主导范式。研究人员随后专注于测试障碍原则的预测，例如测量诚实信号的绝对成本（并使用能量和其他近似成本作为适合度的代理），但很少有人尝试测试 Grafen 的模型。我们表明 Grafen 的模型不支持障碍假说，尽管它们确实支持 Zahavi 的第二个假设，该假设提出男性根据他们的条件和承受成本的能力（以及他们生存的风险）调整他们对性信号表达的投资). 在这种情况下，诚实的信号不会浪费过度投资，而是会演变，因为选择有利于对信号表达进行有效和最佳的投资，并最大限度地降低信号成本。这个想法与障碍假设非常不同，但它被广泛误解并等同于让分原则。此后的理论研究表明，在均衡时支付的信号成本对于维持信号诚实既不充分也不必要，并且诚实可以通过不同的收益和不同的成本来演变。对让分原则的批评越来越多，但他们关注的是格拉芬模型的局限性，而忽略了它不是让分模型的事实。在自适应信号权衡的达尔文框架中可以更好地理解该模型，而不会增加障碍原则的负担和混淆逻辑。Handicap Principle 没有任何理论或实证支持，早该将这一想法引入“光荣退休”。