Natural selection usually favors modest weapon size because cost offsets benefit

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

Categorization

• XREF: The tug-of-war balance of weapon cost vs benefit sets up the arms race conditions later in the book. — connects to: Markets and battlefields select among rifle designs like natural selection acts on weapons; Weapon costliness keeps signals honest by excluding weaker males; Extreme weapon size faces stabilizing, not open-ended, selection in real populations (+26 more)

Related

• Balanced selection keeps most animal weapons modest rather than extreme. (similarity 0.94)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection (similarity 0.94)
• Bigger weapons usually fail because their costs outweigh their benefits (similarity 0.94)
• Extreme weapon size faces stabilizing, not open-ended, selection in real populations (similarity 0.92)
• Species with huge weapons often show weak current selection on them. (similarity 0.90)
• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races (similarity 0.90)
• Markets and battlefields select among rifle designs like natural selection acts on weapons (similarity 0.90)
• Sexual selection can be far stronger than natural selection and drives weapon extremes (similarity 0.89)
• Reproductive success, not survival, drives the largest animal weapons (similarity 0.89)
• Competition for reproduction drives evolution of nature’s biggest weapons (similarity 0.89)
• Weapons evolve only when reproductive benefits exceed costs (similarity 0.89)
• Arms races inevitably stall as weapon costs neutralize reproductive benefits (similarity 0.89)
• Sexual selection drives weapons to extremes because payoffs for winners are enormous. (similarity 0.88)
• Weapon costliness keeps signals honest by excluding weaker males (similarity 0.88)
• Big weapons only benefit males with the reserves to wield them effectively (similarity 0.87)

Broader Connections

• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races #corroborates (0.85) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 22
• Weapons evolve only when reproductive benefits exceed costs #corroborates (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 199
• Sexual selection can be far stronger than natural selection and drives weapon extremes #qualifies (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 177
• Armor evolution tracks a benefit-cost trade-off identical to that shaping animal weaponry #expands (0.50) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 62
• Competition for reproduction drives evolution of nature’s biggest weapons #qualifies (0.50) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 136
• Economic logic explains weapon evolution across virtually all animal species #expands (0.50) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 198