Animal Weapons

by Douglas J. Emlen

  I’d lurk at the edge of the channel, rocking gently on the swells, and wait for each ship to approach. The soft thrum of their turbines would get louder, and the black shadow of their bulk bigger, until they towered over me. White foam splashing softly in the darkness marked the exact location of the bow and, with that as a guide, I’d close to within thirty feet and let the ship come to me. Then, just as the leading edge glided past, walls rising five stories high, tractor-sized anchor poking through a hole fifty feet over my head, I’d paddle as hard and as fast as I could toward the flank. Up to the wall I’d slip, thump paddle on steel, turn, and out I’d go, straight into the five-foot wave. The ships motored on unaffected, oblivious to my silly sport, foam contrails lingering behind them as they disappeared into the distance.

  Never before, or since, was the evolution of vehicle size laid more starkly before me than on those exhilarating nights in a canoe. The ships I played chicken with weighed more than two million times more than my canoe, and they displaced 130 million more pounds of water. Ship designs had come a long way, and selection for efficient transport crafted these gargantuan cargo carriers.

  * * *

  Vehicles are a lot like animals. They burn energy as they travel, and, like animals, they balance bulk and weight with agility and speed. Their shapes evolve over time in response to demands of particular terrains or tasks. Some become specialized for transport, others for speed, still others for fighting. When vehicles start to fight with other vehicles, selection favors characteristics that improve performance in these contests. Often, as with scramble contests or outright chases, this means faster speeds and greater agility, precluding elaborate armor or big, heavy guns. Occasionally, however, when conditions are just right, vehicles with the biggest weapons win. Bigger becomes better, and vehicles get sucked into an arms race.

  Vehicular arms races require the same three ingredients as animal arms races, but it’s trickier to see. In animals, the first two ingredients—competition and economic defensibility—are essential because without them, males have no reason to fight. Together, they create incentive for intense battles: the reason males invest in weapons in the first place. Given strong incentive, the third ingredient then selects for increases in weapon size. Duels cause bigger weapons to fare better than smaller ones, pushing weapon evolution toward greater and greater extremes.

  For vehicles such as ships or airplanes, the first two ingredients are provided by the states that build and use them. Governments fighting other governments justify and motivate a war, causing ship to attack ship. They load and cock the gun. But it’s the details of the confrontations that determine whether the trigger gets pulled—whether bigger vehicles outperform smaller ones—and here, as with animals, the final ingredient tends to be duels.

  * * *

  After centuries of stasis, a single change in technology forever altered the behavior of ancient Mediterranean warships. Around 700 BCE, a simple pole of cast bronze, mounted at the waterline of the bow, turned what had been vessels of transport into weapons.1 Galleys, powered primarily by people pulling oars, began to charge into the sides of other galleys, attempting to breach their hulls and sink them. Ships fought rival ships at close range, and one-on-one, fulfilling the final ingredient of an arms race; faster ships prevailed. Speed required lots of oars, and more oars meant bigger ships.2

  Shipbuilders added oars, added rowers to each oar, and even added entire tiers of oars. In just a few centuries slender ships 10 feet wide and 90 feet long, powered by fifty men, jumped to double-hulled megaships 420 feet long, powered by four thousand men.3 The biggest ships were magnificent, but they’d gotten so big their weight offset the advantage of extra oars. They were too large to be fast, and too awkward to actually close in on and ram their rivals; the pendulum of ship evolution had swung too far and these ships were nautically worthless. For a while they were given new functions. The largest ships had catamaran-style double hulls with wide, stable decks, so they were used to transport catapults and other artillery.4 But by this point the benefits of the biggest ships were not worth their excessive costs. The arms race stalled and the pendulum swung back toward smaller ships, settling eventually on “fives.” One hundred forty feet long and powered by three hundred oarsmen, fives were large and lethal, but not excessive or awkward. Their basic design survived for more than a thousand years after this first naval arms race ended.5

  Not until the sixteenth century did technology and one-on-one-style naval engagements realign to trigger another race. This time it was sparked by the development of a sailing warship, the galleon. Ships propelled by wind rather than oars had sturdy hulls capable of withstanding storms, and they could be handled by smaller crews, so stored provisions lasted long enough for extended voyages on the open ocean.6 Sail-powered ships transformed exploration and commercial shipping, permitting nations with the largest navies to plant colonies around the globe.

  Early galleons had a pair of cannons mounted on their bows, modern equivalents of the battering ram (the first galleons actually carried rams as well, even though these ships were ill-suited for ramming).7 But ships were long and slender, so only a few cannons could fit at the front. Additional cannons could have been added along the upper decks, but they would have been too tippy; weight up on the deck made ships unstable. However, the invention of closeable gun ports—wooden flaps that could be shut tight to keep water out in a storm—permitted cannons to be mounted low on the sides of ships, down near the waterline where they actually made the ships more stable.8

  Sailing galleons could now fire broadsides with lots of cannons, but they had to turn sideways to do it. Ships had to expose their flanks to opponents. They also had to fire from very close range. Smooth-bore cannons were inaccurate under the best of circumstances, but at sea, with rolling hulls shifting back and forth, even the best crews could hit only targets a few hundred yards away. Most of the time, they needed to be much closer than this to have any chance of hitting other ships. Ships started to fight rival ships at very close range—“yardarm to yardarm”—in ship-versus-ship duels and, once again, circumstances became conducive to an arms race.9

  Bigger cannons inflicted more damage than smaller ones, and more cannons were better than fewer. More and bigger cannons required bigger ships, so the sizes of galleons grew. One row of cannons became two, and then two became three. In the fifteenth century warships packed as many as 60 cannons each, but soon they carried 74, and then 100, or even 120, and by the end of the eighteenth century some ships carried as many as 140 cannons.10 The size, extravagance, and cost of sailing warships climbed until a new style of gun—rifle-barreled cannons with exploding shells—rendered wooden-hulled warships obsolete.11 Like the oared galleys before them, the biggest warships were now no longer worth the price.

  For both naval races, a change in ship behavior brought rivals together in new styles of interactions that favored the larger ship. Like beetles beginning to guard burrows or bull caribou starting to lock antlers head-on with rival bulls, bigger ships began to be more effective than smaller ships. Size mattered, and from that point forward it always paid to have the bigger ship. Also like animals, the ship size that performed best was relative—“big” really meant “bigger than everyone else.” The playing field evolved as the ships evolved, with each advance on one side promptly matched and then bested by the other in a back-and-forth cycle that fueled the race. Eventually, the biggest ships just weren’t worth the cost, and the spiral of growth collapsed. Although the details of the confrontations may vary—speed, for example, may be more important than size—the same basic dynamic of one-on-one contests helps explain all sorts of vehicular arms races, from galleons and dreadnoughts to tanks and airplanes.

  * * *

  A mere ten years after Orville and Wilbur Wright soared over sand dunes in Kitty Hawk, North Carolina, aircraft started shooting down other aircraft in battle. At the outset of WWI, airplanes flew reconnaissance missions, skimming over battlefields to recor
d troop movements and locations of major artillery.12 A biplane constructed from cloth and wood, powered by a single propeller engine, could reach speeds of one hundred miles per hour, and information obtained from pilots proved invaluable to commanders in the trenches below. The problem was that both sides appreciated the significance of aerial reconnaissance, and each attempted to prevent the other from gathering it. It didn’t take long before planes from one side started encountering planes from the other, and pilots tried all sorts of clever tricks to force their opponents from the sky. Some hurled bricks at the cockpits of enemy planes; others dangled strands of rope or chain in front of the propellers.13 Many started carrying pistols, firing at enemy pilots as they flew past.

  The first attempts to mount machine guns onto airplanes fared badly; bullets whizzed straight through the spinning propeller, splintering wood when they hit the blades. The French tried a crude fix, mounting steel wedges to the inside of each blade to deflect the bullets, but it was the Germans who finally solved the problem, when they mechanically coupled propellers with the firing mechanism of the machine gun, synchronizing bullets so they shot in between the blades of the propeller.14 Within a matter of weeks the French had copied, and then improved upon, this design, and for the remainder of the war both sides flew planes with forward-facing machine guns.

  Now pilots could challenge other pilots directly, and dogfighting was born. Aerial duels pushed planes to their performance limits, and pilots quickly learned the capabilities of both their own and their opponents’ machines, often attempting to exploit subtle differences in relative speed, climb rate, or turning radius.15 Bigger wasn’t better, but faster speeds and greater maneuverability were, and planes became locked into an arms race just the same. Pilots could occasionally work around limitations of their machines, using clever tactics, skill, or trickery, but the advantage clearly went to the pilot with the superior plane, and each side raced to develop better and better machines. Back and forth the advantage went, as the Germans, then the French and British, and then the Germans again, took the mechanical lead. Model after model hit the skies, each a bit faster and better than the last.16

  The first fighter aircraft attacked rivals in aerial duels, sparking an arms race in aircraft design.

  By the start of WWII, the shapes and styles of military aircraft had diversified, as planes became increasingly specialized for particular tasks. Transport planes were different from reconnaissance planes; fighters were different from lightweight fighter-bombers; and all of these were different from heavy bombers. But fighters still challenged enemy fighters in battles for control of the skies so, for these planes, the race for speed and agility surged on.

  By the end of the war, propeller-driven fighter aircraft such as the U.S. P-51D Mustang could attain speeds of 440 mph, and the German Me 262, the first jet-engine fighter, could fly faster than 500 mph.17 By the Korean War, U.S. F-86 Sabres were dropping out of near supersonic dives to fight high-speed duels with Russian-built Chinese MiG-15s.18 Shortly thereafter, Mach II–enabling afterburner technology and air-to-air missiles further revolutionized fighter design. Now planes were moving so fast that the “G-forces” they generated during turns pushed the physical capacities of pilots to the limit—any faster and pilots blacked out, crashing multimillion-dollar aircraft in the process.19 In modern fighters like the F-16 Fighting Falcon, pilot actions are integrated with sophisticated computer software to control planes during flight (called “fly-by-wire” systems), preventing planes from generating G-forces beyond pilot tolerances.20

  Ironically, fighters soon became limited by how slowly they could fly. Supersonic they could handle, but many dogfights required close-range maneuvers that could only be accomplished at speeds under 500 mph. At these speeds planes often stalled, prompting development of “supermaneuverable” fighter aircraft such as the Russian Su-30 Flanker and the U.S. F-22 Raptor, each with rotatable nozzles permitting jet propulsion to be angled in different directions during flight.21

  August 28, 2013, marked the one hundredth anniversary of the first documented dogfight, when the British pilot Norman Spratt, flying an unarmed Sopwith Tabloid biplane, forced a German Albatros C.I two-seater into the ground.22 Since then, in one of the most rapid of all races, fighter aircraft have surged into supersonic, supermaneuverable beasts with stealth capabilities; sophisticated electronic flight controls, navigation, and targeting; guided air-to-air and air-to-ground missiles; and antimissile defensive measures. But this race, too, has approached its zenith.

  The greatest limit to modern fighter aircraft is the pilot. The newest planes are forced to perform at levels well below what they are capable of. In fact, the primary function of computer-enhanced controls is to hold the plane back, so that the pilot doesn’t pass out.23 Unmanned aeriel vehicles (UAVs), or drones, don’t have these constraints, and already they are replacing traditional aircraft for countless military tasks. UAVs cost tens of millions of dollars less per vehicle than F-16s or F-22s, and even smaller and cheaper planes—“micro air vehicles” with six-inch wingspans—are currently in the works.24 In the not-so-distant future, piloted fighter aircraft may no longer be worth the cost.

  WWII also sparked rapid evolution of bomber aircraft, incidentally, but these planes faced very different challenges. Unlike fighters, who could dodge, roll, or climb as needed to engage rival aircraft, bombers had to fly in straight lines in strict formation. As bombers neared their targets, it was imperative that they held to a constant speed and altitude, so that bombardiers—the men who actually pushed the button to drop the bombs—could aim the bombs onto targets below. So critical was this constancy that pilots handed control of the aircraft over to the bombardier during the final stages of the bombing run. That way, panicked pilots couldn’t alter the course even if they wanted to.25

  Constant flight speeds made bombers predictable targets—“sitting ducks”—not unlike fixed townships and cities, and in many ways the evolution of these planes paralleled the evolution of walled fortifications and castles.26 Bombers did not attack rival bombers, like fighters attacked fighters. Instead, their survival depended upon defense, thwarting the advances of enemy fighters. In these confrontations, exposed planes were dead planes, so rotatable, protruding turrets with machine guns were added to the top and bottom, and guns were added to the nose, tail, and flanks. As with castles, the idea was to leave no flank undefended, and bombers soon carried guns and crew sufficient to provide covering fire to all sides of the craft. Even the names of these planes reflected the defensive logic of their design, such as the B-17 “flying fortress,” or the B-29 “superfortress.” Unfortunately for the crews, these planes still had to remain light enough to fly, so armor plating was limited and the effort to build fortresses of the air short-lived.

  In contrast with fighters, bombers flew straight paths over targets, rendering them especially vulnerable to enemy fire. The evolution of bombers resembled that of castles, as planes became increasingly fortified with defensive turrets and machine cannons positioned to cover all angles of approach.

  * * *

  The grandest scale at which arms races can unfold is between rival states. States are even more like animals than vehicles, gobbling up resources and competing with each other for control of these resources. In the ancient world, the most limiting resources, besides people, arable land, water, and living space, were deposits of copper and tin.27 Metals were hard to come by, and nearly all went into weapons. Today we still fight over arable land, water, and living space; but we also fight over access to energy, primarily in the form of oil. States depend on natural resources for their survival. There aren’t enough to go around, and the result, not surprisingly, is competition. But how states compete—who challenges whom, whether confrontations turn into arms races, and whether arms races escalate to outright war—is more predictable than most people realize.

  When states compete with states, the “individuals” that confront each other are rival governments, and the relev
ant weapons their respective military forces. New states are born from time to time, and other states disappear, but this isn’t the evolutionary turnover that matters here, because arms races between states happen much faster than this, beginning and ending during the political lifetimes of the involved states. Rather, it’s the military establishments within each state that grow or recede. Circumstances conspire to spark an arms race when rivals face each other in such a way that bigger militaries suddenly become much better than smaller ones. The state with more or better weapons gains an advantage that prompts the other side to catch up, launching them both into increasingly extravagant back-and-forth cycles of military spending. States continue to spend, shunting more and more of their resources into weapons, and militaries expand, until the race culminates in outright war; or until one of the states spends beyond what it can sustainably afford and fiscally collapses.

  For political arms races, the best parallel with animals is not the gradual turnover in populations we’ve focused on thus far, but rather a confrontation between two rival males—two crabs, for example, that face off in the sand. Who will back down? An arms race between states erupts in the same way a contest between crabs escalates; neither yields, pushes give way to grabs and jabs, grappling to smashing, and then pounding, and finally unrestricted war. When it comes to warfare, states behave just like crabs on a beach.

  Pick any period in history and glance at a political map. You’ll see big states and little states, and everything in between. Some states are born rich—their borders include vast natural resources, favorable climate, and secure, defensible terrain. Others have almost nothing. Wealthy states have larger total resource pools, or gross domestic products (GDPs), than poorer states, and they can afford to spend more on weapons. To put this in perspective, in 2011 the United States had a GDP of roughly $15 trillion.28 At that time, this was twice the GDP of China, eight times the GDP of Russia, thirty times the GDP of Iran, and four hundred thousand times larger than the GDP of Montserrat and Tuvalu. States differ spectacularly in how much they have available to spend.