15. Surprisingly few studies have actually measured the strength and nature of selection on extreme weapons—it's incredibly labor-intensive to do. But those that have often find that as weapons get bigger and bigger the success of males rises up to a point, beyond which success begins to drop. Males with the very largest weapons tend to do worse than males with slightly smaller weapons. If males with the biggest weapons of all fared the best, selection would be "open-ended" and directional. The fact that the very biggest males did slightly worse shows us that selection in these populations is stabilizing, and it suggests these populations may be at or close to their balance point.

Emlen, Douglas J, Animal Weapons_ The Evoluti…, loc. 850