The Arms Race

Since the beginning of time, Nature's version of the neverending arm race has been employed by an astonishingly wide variety of organisms in order to continue their existence on planet earth. Prominent in this unceasing quest for dominance in all things related to sex, food and habitat, is the dung beetle, an industrious insect whose species include males equipped with bodacious armaments, similar, in indirect fashion, to what the military has in the good old USA. :)

Much as in geopolitics, animal arms races rack up staggering costs. For example, these beetles’ horns can make up 30 percent of a male’s total weight, and because nutrients are redirected to horn growth, males often have stunted eye and reproductive-organ growth. Soon horns become so pricey only a select few can afford them, and once this happens, the sole option left for the rest of the males is to cheat. And so nearly every heavily armed species has small males who break the rules.

Not all O. nigriventris males have horns. Those that don’t grow past a certain size — because they were born smaller or were malnourished — never hit the genetic trigger that leads to horn growth, forcing them to circumvent the whole system of duels in order to breed. Instead of dueling (and losing), small O. nigriventris males dig their own tunnels, bypassing the guarding males in order to mate with the female, and slip back out again undetected. They waste no resources on weapon development at all, leaving them nimbler and even more virile — instead of growing horns, they grow big testes that produce extra sperm. They may not mate with as many females as the larger males of their species, but they make the most of every opportunity.

Over time, this end run around the logic of the arms race can completely upend it, pushing the armed animals out of the gene pool. Overburdened and outmatched, animals with weapons eventually die off. Biologists were baffled when they first encountered this trend — it seemed to fly in the face of sexual-selection theory, which is the notion that the best-armed males will be the most genetically prolific. But much as duels necessarily create arms races, arms races necessarily create cheaters — and cheaters can win, bringing an end to the race.

Sounds like a plan to me.