Animal weapons can evolve rapidly within just seven generations

Evidence

Two years and seven beetle generations later, I had my answer. The weapons had evolved. Males in populations selected for longer horns now sported weapons that were proportionately larger than they had been before, and males in populations selected for shorter horns had weapons that were proportionately smaller. Each of these extremes differed from the populations that had acted as controls, and I’d shown convincingly that animal weapons can evolve fast. But weapons weren’t the only trait that changed; increases in horn size came at a price. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 294

Categorization

• XREF: Feeds the reader’s goal of tracking how warfare evolves; rapid evolutionary response to selection parallels rapid escalation in arms races between rivals. — connects to: Weapon size in animal species is under stabilizing selection, not open-ended directional selection — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 850; Humanity’s oldest art depicts animals with extreme weapons — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 950

Related

• Species with huge weapons often show weak current selection on them. (similarity 0.87)
• Animal weapons evolved to extremes far beyond practical size (similarity 0.87)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection (similarity 0.86)
• Each weapon-size increase resets the competitive baseline, ratcheting populations upward (similarity 0.86)
• The evolutionary drivers of animal weapons also explain human weapon elaboration. (similarity 0.86)
• Human and animal arms races follow parallel evolutionary dynamics (similarity 0.86)
• Identical circumstances trigger and collapse arms races in animals and humans. (similarity 0.85)
• Each escalation in weapon size resets the competitive baseline and triggers the next round (similarity 0.85)
• Competition for reproduction drives evolution of nature’s biggest weapons (similarity 0.85)
• Comparisons of animal and human weapons have a long scholarly tradition. (similarity 0.85)
• Balancing selection normally curbs weapon size until some lineages escape into runaway arms races (similarity 0.85)
• Balanced selection keeps most animal weapons modest rather than extreme. (similarity 0.85)
• Sexual selection stays directionally constant while physical natural selection oscillates (similarity 0.85)
• The same three ingredients trigger weapon evolution across wildly divergent animal clades (similarity 0.85)
• Extreme weapon size faces stabilizing, not open-ended, selection in real populations (similarity 0.84)

Broader Connections

• 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