When balancing selection fails, bigger weapons win every round and escalate the race.

Evidence

Yet, every so often this balance is tipped. Here and there, sprinkled across the tree of life, are animal lineages where modesty of proportion was cast aside. The evolution of weapons in these species surged forward unencumbered. Gone were the shackles of balancing selection, and all that remained was selection favoring bigger and bigger weapon sizes. Here, individuals with the most grotesque or extreme armaments beat opponents with smaller weapons. In so doing, they secured opportunities to breed. Their progeny, as impressive in their weapons as their parents, quickly replaced earlier forms and advanced the population another notch in weapon size. As soon as the next new innovation arose—an even larger or more complex variant of the existing design—the process repeated itself. Again and again, individuals with the newest and biggest weapons won, replacing those with earlier and smaller forms, and this process pushed the population still further on the path to extreme. In short, the weapons of these species got caught up in an arms race. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 22 (#qualifies, via linked claim)

As weapons get bigger they select for increasingly elaborate deterrence, and deterrence, in turn, selects for bigger and bigger weapons. Arms races and deterrence push each other forward, escalating in an evolutionary spiral. Like a figure skater pulling her arms to her chest, the evolution of extreme weapons gets faster and faster. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 390 (#expands, via linked claim)

Categorization

• XREF: connects to: Successful cheaters can reverse selection so big weapons collapse; Each escalation in weapon size resets the competitive baseline and triggers the next round; Balancing selection normally curbs weapon size until some lineages escape into runaway arms races — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 22 (+10 more)

Related

• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races (similarity 0.93)
• Each escalation in weapon size resets the competitive baseline and triggers the next round (similarity 0.92)
• Balanced selection keeps most animal weapons modest rather than extreme. (similarity 0.91)
• Dueling plus competition and defensibility is the general rule for extreme weapons (similarity 0.91)
• Bigger weapons usually fail because their costs outweigh their benefits (similarity 0.90)
• Extreme weapon size faces stabilizing, not open-ended, selection in real populations (similarity 0.90)
• Successful cheaters can reverse selection so big weapons collapse (similarity 0.89)
• Deterrence amplifies the evolutionary payoff of extreme weapon size. (similarity 0.89)
• Each weapon-size increase resets the competitive baseline, ratcheting populations upward (similarity 0.89)
• Arms races inevitably stall as weapon costs neutralize reproductive benefits (similarity 0.89)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection (similarity 0.89)
• Species with huge weapons often show weak current selection on them. (similarity 0.89)
• Sexual selection drives weapons to extremes because payoffs for winners are enormous. (similarity 0.89)
• Extreme skew in mating success drives arms-race escalation in weaponry (similarity 0.88)
• Specific conditions are required before weapons escalate into an arms race (similarity 0.88)

Broader Connections

• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races #qualifies (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 22
• Bigger weapons usually fail because their costs outweigh their benefits #contradicts (0.65)
• Each escalation in weapon size resets the competitive baseline and triggers the next round #expands (0.60)
• Each weapon-size increase resets the competitive baseline, ratcheting populations upward #expands (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 183
• Big weapons only pay off when fights are one-on-one duels #qualifies (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 238
• Weapon escalation ends when costs outweigh benefits and cheaters invade #qualifies (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 457
• Weapon evolution and deterrence form a self-accelerating spiral. #expands (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 390
• Symmetrical one-on-one fights are a neglected prerequisite for weapon arms races #qualifies (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 226
• Concentrating simultaneous fire disfavors large weapons while duels favor them #qualifies (0.60)
• Dueling plus competition and defensibility is the general rule for extreme weapons #qualifies (0.55) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 266
• Weapon evolution needs both competition and economically defensible resources #qualifies (0.55) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 191
• Weapons in arms races get so big they impair other bodily functions #expands (0.50)