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set of antlers has paid the costs of growth, and is thus, a serious opponent with considerable strength. A tall, heavy, long-tusked elephant bull has spent the time and energy to bulk up, and can throw this weight around in a fight. Added on to an animal’s RHP are dynamic properties, features that require energetic investment in the moment such as the loudness or duration of a vocalization, or the height of a jump display. These dynamic properties form the foundation of competitive interactions, and the raw material for assessments. When a resource is up for grabs, and no simple rule of thumb or RHP factor trumps, animals assess each others’ displays, working out whether to flee or escalate. What, if anything in a display, reflects the signaler’s true capacity and motivation? The Israeli evolutionary biologist Amotz Zahavi provided a simple, yet far-reaching explanation of honest signaling. Honesty, in the animal world, is simply about prediction. When a kob standing on his territorial mound charges toward another, to what extent does this display predict that he will continue the attack if the opponent doesn’t flee? Is he all smoke or does the display accurately predict the follow- through? When a mantis shrimp uses his powerful claw to thump the sand at an intruder, will he go further, thumping the intruder who continues to advance? Zahavi’s solution was based in economics: signals are honest if and only if they are costly to produce, where cost is relative to current condition or health. If every kob can charge even if they are blowing smoke, the charge display carries no weight. It is pure puffery and dishonest. If every mantis shrimp can thump with its appendage, and does so regardless of its current power, then sand thumping loses value. For a charging display or sand thumping to carry value, they have to be costly to produce and only those in good enough condition should be able to tolerate the costs. Numerous studies support Zahavi’s insight, including work on insects, crabs, birds, and gazelles, as well as hunter-gatherers and religious institutions. Hunter-gatherers do it by showing off and sharing their large prey capture, whereas religions do it by showing their commitment to long and involved ritual displays. The vast majority of animal competition is settled by means of non-lethal aggression. Animals adopt different strategies, use rules of thumb, and engage in assessment in order to minimize the costs of battle. This is version 1.0 of HARMING OTHERS. This version operates within every animal, humans included. Over time, some animals evolved hormonal and neural upgrades that changed how individuals experienced the thrill of victory and the agony of defeat, as well as changes in their willingness to take risks. These upgrades inched animals closer to lethal aggression, pushed some right into it, and others over the top. Hauser Chapter 1. Nature’s secrets 35 HOUSE_OVERSIGHT_012781