The Norman Transcript

November 14, 2013

Emlen makes animal, human parallels

By Katherine Parker
The Norman Transcript

NORMAN — From flies to crabs, beetles and elk, every animal has a weapon of sorts. Usually, these weapons are in proportion to the overall size of the animal and provide a balance such that animals may effectively hunt, kill and feed on prey.

However, in some cases, animals are fitted with extreme weapons breaking away from balance. Biologist Doug Emlen, of the University of Montana, discussed his book “Extravagant Weapons” Thursday night and what triggers the evolution of extreme weapons in animals and how this parallels the evolution of human weapons technology.

A part of the University of Oklahoma Sutton Lecture Series, Emlen revealed what three critical prerequisites must be in place for extreme weapons to evolve and an arms race to ensue.

“Most weapons — claws, teeth and talons — stay small because of balance. Big weapons may be critical to killing but may hinder catching prey or eating. Balance allows hunters to do both,” Emlen said. “There are two basic ways balance breaks down: 1) counteracting selection disappears ... and 2) competition over reproduction.”

He said when a predator ambushes his prey, the cost of a big weapon is minimal. Because a female’s turnaround for reproducing takes much longer than a male’s, fewer females are available for mating, resulting in intense competition.

Yet, some species, including birds, effectuate this competition by singing the loudest songs, flashing the brightest colors and having the biggest plumage. Three prerequisites must be in place to push forward the development of extreme weapons in an animal arms race, Elmen said.

Not only must there be intense competition and a limiting/defensible resource, but contests over limited resources must occur in the form of duels and not mere scrambles.

“Scrambles require agility. Extreme weapons are not cost effective as opposed to duels, which are predictable and favor strength, skill and weaponry,” Emlen said.

Emlen described his work with dung beetles and how the above-described perquisites can cause the development of extreme weapons in part of the species.

Some dung beetles roll dung into balls and have to deal with scrambles with other dung beetles to protect their food source. Other dung beetles that live in the same habitat and have the same available resources take dung down to the bottom of a tunnel they have dug. These tunnel-digging dung beetles have developed horns.

Emlen said dung beetles that dig tunnels must protect their food source from beetles who try and go down the tunnel, creating a one-on-one fight. In a duel, extreme weapons are an asset.

“One simple change in how they get and hide their food resource changed their weaponry,” Emlen said, adding that the same set of conditions set off arms races in the human species.

“Changes in technology aligned male fights, so they met in duels and weapons became extreme,” he said.

Emlen described the development of closeable gun ports on ships and how such technology forced battles to be fought in close range, one-on-one, and gave bigger ships the advantage. Ships became longer and were built to hold more than one row of cannons, Emlen said.

“Just like the dung beetles, changes in human technology aligns with face-to-face duels,” he said.

Extreme weapons also may serve as signals or deterrents, Emlen said. With animal species, bigger weapons serve as a proxy for fighting ability and deter duels.

He said there is a paradox of peace related to extreme weapons, and extreme weapons have acted as deterrents in human controversies, as well, such as the Cold War. Emlen said he believes there still is much to be learned from the development of extreme weapons in animal species.

“There really are parallels between animals and ourselves, and there are insights to be gleaned from beetles, crabs and caribou,” Emlen said.

The George Miksch Sutton Lectureship was established in 1972 by an endowment from George Miksch Sutton, who was an ornithologist, conservationist and artist. Sutton served as George Lynn Cross Professor of Zoology at OU. The Sutton Lecture Series brings biologists to OU to present lectures about natural history.

Katherine Parker


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