Extreme skew in mating success drives arms-race escalation in weaponry

Evidence

In the animal world, extreme weapons are usually confined to specific, rare circumstances such as sit-and-wait hunting tactics, or within-colony division of labor. But another surprisingly potent phenomenon can lead to the evolution of exaggerated weapon sizes: competition. Nature’s biggest weapons decide the outcomes of battles over the chance to reproduce, the most precious commodity of all. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 136 (#expands, via linked claim)

To use the same basic equation I allude to in the text, the benefits of having big weapons (B), representing the offspring produced by the females they guard, are offset by production, maintenance, and fighting costs (C). When B − C > 0, then selection drives the evolution of weapons toward ever greater size. What’s not shown is our assumption that males are gleaning 100 percent of the fertilizations of the females they defend: (1 * B) − C > 0. Cheating males erode the rewards to dominant males, so that they reap only a fraction of the sired offspring that they otherwise would have. In the hypothetical beetle example where sneak males, on average, steal one-fourth of the fertilizations, the new equation would be: (0.75 * B) − C > 0. Benefits are devalued by the proportion of fertilizations stolen by cheaters (1 − 0.25 = 0.75). At some point, if cheaters steal enough, the realized benefits may be low enough that they no longer exceed the costs, even for the most successful guarding males. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 851 (#qualifies, via linked claim)

Categorization

• XREF: connects to: Cheating males erode the reproductive payoff of weapons, capping their evolution — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 851; Competition for reproduction drives evolution of nature’s biggest weapons — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 136; Sexual selection can be far stronger than natural selection and drives weapon extremes — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 177 (+21 more)

Related

• Sexual selection drives weapons to extremes because payoffs for winners are enormous. (similarity 0.93)
• Cheating males erode the reproductive payoff of weapons, capping their evolution (similarity 0.92)
• Successful cheaters can reverse selection so big weapons collapse (similarity 0.92)
• Weapon costliness keeps signals honest by excluding weaker males (similarity 0.91)
• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races (similarity 0.91)
• Reproductive success, not survival, drives the largest animal weapons (similarity 0.90)
• Sexual selection can be far stronger than natural selection and drives weapon extremes (similarity 0.90)
• Weapon escalation ends when costs outweigh benefits and cheaters invade (similarity 0.89)
• Competition for reproduction drives evolution of nature’s biggest weapons (similarity 0.89)
• Arms races inevitably stall as weapon costs neutralize reproductive benefits (similarity 0.89)
• When balancing selection fails, bigger weapons win every round and escalate the race. (similarity 0.88)
• Monopolized reproduction drives males of many species to cheat (similarity 0.88)
• Male combat for mating access frequently causes serious wounds and sometimes death (similarity 0.87)
• Bigger weapons usually fail because their costs outweigh their benefits (similarity 0.87)
• Each escalation in weapon size resets the competitive baseline and triggers the next round (similarity 0.87)

Broader Connections

• Competition for reproduction drives evolution of nature’s biggest weapons #expands (0.85) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 136
• Cheating males erode the reproductive payoff of weapons, capping their evolution #qualifies (0.80) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 851
• Sexual selection drives weapons to extremes because payoffs for winners are enormous. #expands (0.80)
• Sexual selection can be far stronger than natural selection and drives weapon extremes #expands (0.75) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 177
• Weapons evolved as signals so males could predict fight outcomes before risking battle #corroborates (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 370
• Deterrence amplifies the evolutionary payoff of extreme weapon size. #expands (0.65) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 387
• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races #contradicts (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 22
• Arms-race weapon growth makes resource trade-offs drastically impair body functions #expands (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 296
• Shared clade traits like lengthy female investment predispose entire lineages to weapon arms races #qualifies (0.55) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 268