The same three ingredients trigger weapon evolution across wildly divergent animal clades

Evidence

What these broad patterns reveal is a simple and surprisingly universal rule: after the final ingredient for arms races falls into place, entire clades of descendant species can all experience rapid evolution of extreme male weapons. Mastodons and flies could not be more different from each other. They lived at different times, in different habitats, and fed on different foods. One was more than 120 million times the size of the other. One had enlarged teeth, and the other had chitin protrusions from the forehead. Yet, the same three ingredients triggered evolution of extreme weapons in both cases. So it is with wasps, beetles, crabs, earwigs, elephants, and antelope. Despite extraordinary differences among these species, arms races are arms races, and the circumstances leading to big weapons are the same. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 277 (#corroborates, via linked claim)

Such is the reality of extreme animal weapons. Brutal and beautiful, extreme weapons have cropped up repeatedly during the unfolding of the history of life. All told, some three thousand species now wield them. That’s a drop in the bucket considering there are 1.3 million described types of animal, but it’s a collection packed with remarkable creatures. Early champions include the horns of triceratops, titanotheres, and trilobites, the tusks of mammoths and dolphins, and the racks of Irish elk. Today, extreme weapons are wielded by walruses, antelope, whales, crabs, shrimp, beetles, earwigs, plant bugs, and flies, to name just a few. The weapons themselves can be matted hair, bone, teeth, or chitin, and they take any number of different forms. Some, for example, are overgrown versions of an existing structure, like a tooth or a leg. Others appear to have arisen de novo, as new bumps or knobs that became so large they formed their own distinct structure. — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 15 (#expands, via linked claim)

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)

Categorization

• XREF: connects to: Identical triggers drive extreme weapon evolution across wildly unrelated clades — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 277; Extreme weapons evolved independently across roughly three thousand species — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 15; Economic logic explains weapon evolution across virtually all animal species — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 198 (+6 more)

Related

• Identical triggers drive extreme weapon evolution across wildly unrelated clades (similarity 0.96)
• Extreme weapons evolved independently across roughly three thousand species (similarity 0.93)
• Competition for reproduction drives evolution of nature’s biggest weapons (similarity 0.90)
• The evolutionary drivers of animal weapons also explain human weapon elaboration. (similarity 0.87)
• Reproductive success, not survival, drives the largest animal weapons (similarity 0.86)
• Dueling plus competition and defensibility is the general rule for extreme weapons (similarity 0.86)
• Animal weapons evolved to extremes far beyond practical size (similarity 0.86)
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection (similarity 0.86)
• Economic logic explains weapon evolution across virtually all animal species (similarity 0.86)
• Biological weapons evolve through the same replication mechanism as their bearers (similarity 0.86)
• Extreme male weapons evolved independently at least eleven times in vinegar flies (similarity 0.86)
• Specific conditions are required before weapons escalate into an arms race (similarity 0.86)
• Three conditions must align to trigger an animal weapons arms race. (similarity 0.85)
• Extreme weapon size faces stabilizing, not open-ended, selection in real populations (similarity 0.85)
• Dung beetles offer the ideal study system for extreme weapon evolution. (similarity 0.85)

Broader Connections

• Identical triggers drive extreme weapon evolution across wildly unrelated clades #corroborates (0.95) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 277
• Extreme weapons evolved independently across roughly three thousand species #expands (0.70) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 15
• Competition for reproduction drives evolution of nature’s biggest weapons #expands (0.60) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 136
• Economic logic explains weapon evolution across virtually all animal species #qualifies (0.50) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 198
• Weapon size in animal species is under stabilizing selection, not open-ended directional selection #contradicts (0.50) — Emlen, Douglas J, Animal Weapons_ The Evolution of Battle, 850