Bigger weapons usually fail because their costs outweigh their benefits

Evidence

Huge animal weapons look too awkward to be favored by selection, and in the vast majority of cases, this appearance isn’t misleading. Big weapons are ungainly, and most individuals fare poorly with them. For most weapons in most species, selection favors modest size and minimal cost—enough tooth to bite or grab prey, for example, but not enough to slow you down or impair your ability to maneuver. What this actually means is that selection on weapons is balanced: bigger weapons may be better for stabbing or biting, but they are also more expensive to produce and more difficult to carry. The result is a tenuous balance, much like a game of tug-of-war, which accounts for the multitude of unimpressive weapons adorning the vast majority of animal species. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 21 (#corroborates, via linked claim)

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 (#corroborates, via linked claim)

In the end, the fate of all weapons comes back to benefits and costs. Early in arms races the payoffs for big weapons may soar. But circumstances change. Costs climb and cheaters invade, gouging profits until big weapons reach a point that’s unsustainable: the rewards no longer justify the expense. From that point forward, they’re just a liability. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 457 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Arms races inevitably stall as weapon costs neutralize reproductive benefits — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 432; Some elaborate animal weapons are astonishingly cheap to produce and carry; When balancing selection fails, bigger weapons win every round and escalate the race. (+11 more)

Related

• Natural selection usually favors modest weapon size because cost offsets benefit (similarity 0.94)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection (similarity 0.92)
• Balanced selection keeps most animal weapons modest rather than extreme. (similarity 0.91)
• Extreme weapon size faces stabilizing, not open-ended, selection in real populations (similarity 0.91)
• Weapons evolve only when reproductive benefits exceed costs (similarity 0.91)
• Big weapons only benefit males with the reserves to wield them effectively (similarity 0.90)
• Weapon costliness keeps signals honest by excluding weaker males (similarity 0.90)
• Reproductive success, not survival, drives the largest animal weapons (similarity 0.90)
• When balancing selection fails, bigger weapons win every round and escalate the race. (similarity 0.90)
• Arms races inevitably stall as weapon costs neutralize reproductive benefits (similarity 0.90)
• Species with huge weapons often show weak current selection on them. (similarity 0.88)
• Poor-quality males pay steeper costs for large weapons and so invest less (similarity 0.88)
• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races (similarity 0.88)
• Sexual selection drives weapons to extremes because payoffs for winners are enormous. (similarity 0.88)
• Only a minority of males can afford to build full-size weapons (similarity 0.88)

Broader Connections

• Natural selection usually favors modest weapon size because cost offsets benefit #corroborates (0.90) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 21
• Weapons evolve only when reproductive benefits exceed costs #corroborates (0.85) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 199
• Weapon escalation ends when costs outweigh benefits and cheaters invade #corroborates (0.80) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 457
• Big weapons only benefit males with the reserves to wield them effectively #corroborates (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 355
• Weapon costs follow the same handicap economics in nations as in individuals #expands (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 924
• Growing large weapons diverts resources and stunts other body parts #expands (0.50) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 295