We've identified two of the three critical ingredients for arms races: intense competition, generally arising among males as they battle for access to females, and ecological situations that cause resources to be localized and economically defensible. There's one final ingredient, and it involves the details of the fights themselves—the way that males face each other in battle. Males must face each other one on one, rather than all together in a scramble. For bigger weapons to perform better than smaller ones, the battles must be matched and "symmetrical," with comparably armed contestants challenging each other face-to-face. … Oddly, this last ingredient has been almost entirely overlooked by biologists. To appreciate its significance, we must turn instead to attrition models of military forces, and to the century-old insights of an eclectic automotive and aeronautical engineer.

Emlen, Douglas J, Animal Weapons_ The Evoluti…, loc. 226