Each weapon-size increase resets the competitive baseline, ratcheting populations upward

Evidence

Imagine a population of rhinoceros beetles where the average length of male horns is one-half inch. In this social environment, a few males stand out. A mutation increasing horn growth has given them three-fourths-inch horns. These males win battles the most frequently; they mate with the greatest proportion of female beetles; and they populate later generations with disproportionate numbers of their kind (including sons wielding three-fourths-inch horns). Over the next few dozen generations, the population shifts. It evolves in response to sexual selection so that now the average size of horns is three-fourths inches. … The benefits of a three-fourths-inch horn aren’t so great anymore, because now everybody has horns this big. The evolutionary increase in horn length reset the standard for male competition. Into this new social milieu another mutation arises, this time leading to a one-inch horn. Males with these new alleles now have longer horns than their opponents, and they begin to win. So the new alleles sweep through the population as the largest horned males outcompete the earlier, three-fourths-inch rivals, until the population has evolved to this new weapon size. The scale has shifted once again. The population has ratcheted up to the new norm, and it stands poised and ready for the next mutation leading to still another increase in weapon size. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 183

Categorization

• XREF: The ratchet process mirrors runaway selection concepts from Fisherian sexual selection theory. — connects to: When balancing selection fails, bigger weapons win every round and escalate the race.; 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 (+7 more)

Related

• Each escalation in weapon size resets the competitive baseline and triggers the next round (similarity 0.96)
• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races (similarity 0.90)
• When balancing selection fails, bigger weapons win every round and escalate the race. (similarity 0.89)
• Extreme weapon size faces stabilizing, not open-ended, selection in real populations (similarity 0.89)
• Sexual selection can be far stronger than natural selection and drives weapon extremes (similarity 0.89)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection (similarity 0.88)
• Reproductive success, not survival, drives the largest animal weapons (similarity 0.88)
• Competition for reproduction drives evolution of nature’s biggest weapons (similarity 0.88)
• Deterrence amplifies the evolutionary payoff of extreme weapon size. (similarity 0.88)
• Sexual selection drives weapons to extremes because payoffs for winners are enormous. (similarity 0.87)
• Balanced selection keeps most animal weapons modest rather than extreme. (similarity 0.87)
• Sexual selection stays directionally constant while physical natural selection oscillates (similarity 0.87)
• Species with huge weapons often show weak current selection on them. (similarity 0.87)
• Natural selection usually favors modest weapon size because cost offsets benefit (similarity 0.87)
• Extreme skew in mating success drives arms-race escalation in weaponry (similarity 0.87)

Broader Connections

• Weapon evolution and deterrence form a self-accelerating spiral. #expands (0.80) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 390
• Competition for reproduction drives evolution of nature’s biggest weapons #corroborates (0.75) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 136
• Deterrence amplifies the evolutionary payoff of extreme weapon size. #corroborates (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 387
• Extreme weapon size faces stabilizing, not open-ended, selection in real populations #contradicts (0.70)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection #contradicts (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 850
• Natural selection usually favors modest weapon size because cost offsets benefit #contradicts (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 21
• Weapon size honestly signals fighting ability because growth tracks health and nutrition #qualifies (0.50) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 371