Each escalation in weapon size resets the competitive baseline and triggers the next round

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 (#corroborates, 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)

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 (#expands, via linked claim)

Categorization

• XREF: connects to: When balancing selection fails, bigger weapons win every round and escalate the race.; Each weapon-size increase resets the competitive baseline, ratcheting populations upward — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 183; Balancing selection normally curbs weapon size until some lineages escape into runaway arms races — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 22 (+1 more)

Related

• Each weapon-size increase resets the competitive baseline, ratcheting populations upward (similarity 0.96)
• When balancing selection fails, bigger weapons win every round and escalate the race. (similarity 0.92)
• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races (similarity 0.92)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection (similarity 0.87)
• Extreme weapon size faces stabilizing, not open-ended, selection in real populations (similarity 0.87)
• Balanced selection keeps most animal weapons modest rather than extreme. (similarity 0.87)
• Deterrence amplifies the evolutionary payoff of extreme weapon size. (similarity 0.87)
• Dueling plus competition and defensibility is the general rule for extreme weapons (similarity 0.87)
• Extreme skew in mating success drives arms-race escalation in weaponry (similarity 0.87)
• Competition for reproduction drives evolution of nature’s biggest weapons (similarity 0.86)
• Species with huge weapons often show weak current selection on them. (similarity 0.86)
• Arms races inevitably stall as weapon costs neutralize reproductive benefits (similarity 0.86)
• Sexual selection can be far stronger than natural selection and drives weapon extremes (similarity 0.85)
• Reproductive success, not survival, drives the largest animal weapons (similarity 0.85)
• Animal weapons can evolve rapidly within just seven generations (similarity 0.85)

Broader Connections

• Each weapon-size increase resets the competitive baseline, ratcheting populations upward #corroborates (0.90) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 183
• Weapon evolution and deterrence form a self-accelerating spiral. #expands (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 390
• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races #expands (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 22