Weapons evolve only when reproductive benefits exceed costs

Evidence

Nature is the ultimate economizer, relentlessly culling individuals who allocate resources poorly. Over time, we expect that populations will evolve to become increasingly efficient in their use of resources, investing in the growth of large structures such as weapons only when the benefits of having them outweigh any associated costs—that is, when they are cost-effective. By any measure, weapons are costly. They are expensive to produce, and they are expensive to use. Males incur risks when they fight, and fighting requires time and energy that could be expended on feeding and other life tasks. However, males with the largest weapons may derive significant reproductive benefits if these weapons help them secure access to females and keep rival males away. When the reproductive rewards are high enough, even extravagant weapons can be cost-effective. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 199

Categorization

• XREF: connects to: Arms races inevitably stall as weapon costs neutralize reproductive benefits — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 432; States spend on weapons only after mandatory survival costs, like crabs — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 556; Bigger weapons usually fail because their costs outweigh their benefits (+20 more)

Related

• Weapons grow late because development prioritizes mandatory survival expenses first (similarity 0.91)
• Weapon evolution needs both competition and economically defensible resources (similarity 0.91)
• Specific ecological circumstances must align before weapon arms races begin (similarity 0.91)
• Bigger weapons usually fail because their costs outweigh their benefits (similarity 0.91)
• Competition for reproduction drives evolution of nature’s biggest weapons (similarity 0.90)
• Economic logic explains weapon evolution across virtually all animal species (similarity 0.90)
• Weapon growth widens the gap between the best- and worst-armed males. (similarity 0.90)
• Reproductive success, not survival, drives the largest animal weapons (similarity 0.89)
• Big weapons only benefit males with the reserves to wield them effectively (similarity 0.89)
• Weapon expense is what keeps signals of fighting ability honest (similarity 0.89)
• Natural selection usually favors modest weapon size because cost offsets benefit (similarity 0.89)
• Arms races inevitably stall as weapon costs neutralize reproductive benefits (similarity 0.89)
• Only a minority of males can afford to build full-size weapons (similarity 0.89)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection (similarity 0.88)
• Poor-quality males pay steeper costs for large weapons and so invest less (similarity 0.88)

Broader Connections

• Economic logic explains weapon evolution across virtually all animal species #corroborates (0.85) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 198