Számadó Szabolcs, Zachar István, Penn Dustin J
Department of Sociology and Communication, Budapest University of Technology and Economics, Budapest, Hungary.
CSS-RECENS Research Group, ELTE Centre for Social Science, Budapest, Hungary.
J Evol Biol. 2026 Feb 2;39(2):171-189. doi: 10.1093/jeb/voaf144.
Honest signals have long posed a challenge for evolutionary biologists to explain. Here, we propose a general Darwinian theory of signalling, signalling trade-off theory, to explain both honest and dishonest signalling based on recent theoretical and empirical developments. The leading explanation for honest signalling has been the handicap principle (HP), which argues that signals are honest because they are costly. We summarize the main reasons why the HP-and the related costly signalling paradigm-can be fully rejected. Instead, we propose an alternative and more general explanation for honest signalling. The acceptance of the erroneous HP was based on misinterpretations of early signalling models. These models contrary to common interpretations, show that signals are honest, not because they are costly (handicaps), but because cheating (deception) is costly. Deception is costly due to differential signalling costs or differential benefits, or more generally differential trade-offs (i.e., an antagonistic constraint between two functions). Trade-offs are the basis evolutionary life-history theory, and we argue that they are also central to explaining signal honesty and deception. Unlike costs, trade-offs can fully represent both aspects of an investment (marginal cost vs. marginal benefit) over different timescales arising in evolutionary analyses. We examine the alternative explanations proposed to explain honest signalling, such as indices and social punishment, and show that these hypotheses require trade-offs, despite being overlooked. We examine more recent theoretical models that demonstrate that signalling trade-offs maintain honesty, even without signalling costs (handicaps) at the evolutionary equilibrium. Moreover, we show that differential trade-offs are both necessary and sufficient to explain honest signals in cases with conflict of interest. Based on these advances, we argue that differential signalling trade-offs provide a general evolutionary explanation for both dishonest and honest signals and also unify earlier alternative proposals about signal honesty. Finally, we demonstrate that short-term investments under trade-offs at the proximate level (once considered handicap mechanisms) can result in long-term fitness benefits, which thus integrates proximate and evolutionary explanations for signal honesty. We also address how results from sexual selection studies (e.g., terminal investment) are consistent with our theory.
长期以来，诚实信号一直是进化生物学家难以解释的一个难题。在此，我们提出一种信号传递的广义达尔文理论——信号传递权衡理论，以基于近期的理论和实证进展来解释诚实信号和不诚实信号。对诚实信号的主要解释一直是“不利条件原理”（HP），该原理认为信号是诚实的，因为它们代价高昂。我们总结了可以完全摒弃HP以及相关的高成本信号传递范式的主要原因。相反，我们为诚实信号提出了一种替代的、更广义的解释。对错误的HP的接受是基于对早期信号模型的误解。与常见解释相反，这些模型表明信号是诚实的，并非因为它们代价高昂（不利条件），而是因为欺骗是有代价的。由于信号传递成本差异或收益差异，或者更广义地说，由于权衡差异（即两种功能之间的对抗性约束），欺骗是有代价的。权衡是进化生命史理论的基础，我们认为它们对于解释信号的诚实性和欺骗性也至关重要。与成本不同，权衡能够在进化分析中出现的不同时间尺度上充分体现一项投资的两个方面（边际成本与边际收益）。我们研究了为解释诚实信号而提出的替代解释，比如指标和社会惩罚，并表明这些假设需要权衡，尽管它们被忽视了。我们研究了更新的理论模型，这些模型表明，即使在进化均衡中没有信号传递成本（不利条件），信号传递权衡也能维持诚实性。此外，我们表明，在存在利益冲突的情况下，差异权衡对于解释诚实信号既是必要的也是充分的。基于这些进展，我们认为差异信号传递权衡为不诚实信号和诚实信号都提供了一种广义的进化解释，并且还统一了关于信号诚实性的早期替代提议。最后，我们证明在近端水平上权衡下的短期投资（曾经被认为是不利条件机制）能够带来长期的适应性益处，从而将信号诚实性的近端解释和进化解释整合起来。我们还讨论了性选择研究的结果（例如终期投资）如何与我们的理论相一致。
