Shadows of Forgotten Ancestors

by Carl Sagan

  study of natural history become!

  CHARLES DARWIN,

  The Origin of Species1

  Order. Hierarchy. Discipline.

  BENITO MUSSOLINI,

  proposed national slogan2

  The two pit vipers slither toward one another in silence, forked tongues flickering. Slowly they entwine in a languorous embrace. They raise themselves higher and higher off the ground. The glistening coils ebb and flow. Like some macroscopic echo of their underlying microscopic reality, they form a double helix.

  Once, observers concluded that this is a reptilian courtship dance. They neglected to capture the snakes, though, and determine their sexes. When this is done, both snakes turn out to be male So what are they doing? Since homosexual embraces are known throughout the animal kingdom, it still might be a courtship dance—except that it usually ends with one snake toppling the other to the ground, no overt sexual acts having transpired. Instead, this hypnotizing serpentine ritual seems to be a competition, like arm wrestling, played by strict rules. No combatant has ever been bitten or even injured, so far as we know. When the duel ends, whoever has been forced over accepts defeat and slithers away.

  Is this contest about access to females? Sometimes there’s no female in evidence, urging her champion on, or available as a reward for the victor. At the least, this is a struggle over hierarchy, over who’s the top viper—which does not exclude the possibility that the encounter is homosexual as well: Male competition for dominance expressed in homosexual metaphor is a theme widespread among the animals.

  Losing the struggle is apparently a blow to the snake’s self-confidence. He seems morose and demoralized, unable many days later to defend himself against even weakling rivals. Here’s one mechanism by which struggles for dominance later convert into mating success: A female viper, on meeting a lone male, will mimic male behavior and raise herself up as if preparing for this sportive combat. If, still despondent from his last defeat, he does not with sufficient vigor rise to the occasion, she looks elsewhere for a mate.3 Almost without exception, the females manage to mate with the winners.4

  Among pit vipers,5 a male will take one or more sexually receptive females under his “protection” and do what he can to discourage the approach of other males. He will defend or compete for specific territories, especially those that contain resources important for the next generation of vipers. The most celebrated American pit viper, the prairie rattlesnake, does not mate as it comes out of hibernation in the spring, but waits until the late summer when a male must make a considerable effort to track down a female.

  In contrast, the garter snakes of Manitoba hibernate in enormous dens of perhaps ten thousand individuals, the proverbial snake pit. In springtime, the females are sexually receptive as they emerge, one at a time, from the den. And a good thing, too: Waiting impatiently is a gang of several thousand males, who pounce on each female as she exits, forming a writhing, orgiastic, but largely infecund “mating ball.” Competition among the males is fierce, both pre- and post-coitus; after mating, the victor will insert a vaginal plug so no rivals can succeed if he has failed to impregnate the object of his affections. Even among snakes there is a core of basic behavior—including dominance, territoriality, and sexual jealousy—that humans have no trouble recognizing.

  ——

  With very few exceptions, animal societies are not democracies. Some are absolute monarchies, some fluid oligarchies, some—especially on the female side—hereditary aristocracies. Dominance hierarchies exist in almost all, except for the most solitary, species of birds and mammals. There’s a rank order based mainly on strength, size, coordination, courage, bellicosity, social intelligence. Sometimes you can predict, just by looking, who’s dominant: the stag with the most points on his antlers, say, or that large, spectacularly well-muscled gorilla with the silver back. In other cases it’s someone you wouldn’t have guessed, someone without imposing physical stature, someone whose leadership qualities may be apparent to the animals you’re observing but not to you.

  The dominant animal—as determined in ritualized or occasionally in earnest combat—is called “alpha” after the first letter of the Greek alphabet. After alpha comes beta, then gamma, delta, zeta, eta … and so on down to omega, the last letter of the Greek alphabet. Most often, alpha lords it over beta, who makes appropriate indications of submission; beta over gamma, gamma over delta, and so on down the hierarchy.* The alpha male might exhibit dominance behavior in the male hierarchy 100% of the time, the omega male or males 0% of the time, with those in between showing intermediate frequencies

  Apart from the dubious intrinsic satisfaction of intimidating others, high rank often carries with it certain practical benefits—the privilege of dining first and from the choicest morsels, say, or the right to have sex with whomever strikes your fancy. The most passionate enthusiasts of dominance hierarchies are almost always the males, although loosely parallel female dominance hierarchies occur in many species Males generally dominate all females and all juveniles. Among the comparatively rare species in which females sometimes dominate males are the vervet monkeys, the very same who keep their cool when overcrowded.

  While privileged access to desirable females is not the invariable accompaniment of high rank, it is a frequent benefit In a population of mice, the top third of the hierarchy was responsible for 92% of the inseminations. In a study of elephant seals, the bulls in the top 6% of the dominance hierarchy impregnated 88% of the cows.6 High-ranking males often work hard to prevent lower-ranking males from inseminating the females. Females sometimes act to incite rivalry among the males.7 If the dominant males are going to father almost all the children, then clearly there’s a major selective advantage to being a dominant male. Whatever inherited qualities predispose to accomplishing, maintaining, and enjoying dominance will swiftly be established throughout the population—or at least among the males. Social and individual constitutions will be reconfigured by evolution to this end. Indeed, there seem to be parts of the brain in charge of dominance behavior.8

  Promotion in rank does not usually occur because of community social work or fighting off invaders. Promotion comes mainly from combat within the group—mainly ritualized, sometimes real. Darwin clearly understood how natural selection might bring this about:

  The law of battle for the possession of the female appears to prevail throughout the whole great class of mammals. Most naturalists will admit that the greater size, strength, courage, and pugnacity of the male, his special weapons of offence, as well as his special means of defence, have been acquired or modified through that form of selection which I have called sexual. This does not depend on any superiority in the general struggle for life, but on certain individuals of one sex, generally the males, being successful in conquering other males, and leaving a larger number of offspring to inherit their superiority than do the less successful males.9

  If you’re a second lieutenant in the hierarchy and wish to be promoted, you challenge your first lieutenant; he would challenge his captain; he his major; and so on, up the ladder. In this respect at least, animal dominance hierarchies and human military hierarchies differ. Perhaps certain dog-eat-dog corporate hierarchies provide a better parallel. In the case of a successful challenge, the two animals sometimes exchange status, silver bars for gold. Animals weakened by disease, injury, or age are generally broken to the ranks.

  “This town ain’t big enough for the both of us” isn’t the way dominance hierarchies usually work. Faced with a testy alpha male, you have another option besides fight or flight. You can submit. Almost everybody does. Subordinate males ingratiate themselves to those at the top of the hierarchy through incessant bowing and scraping. From their proximity to power those next in rank tend to gain access to food and to females, the leavings of the alphas. Sometimes dominant males are so busy with their police functions that those lower in the hierarchy can arrange sexual trysts that never would have been permitted had the alphas been less pre
occupied. Surreptitious fertilization of females when the alpha male isn’t looking is called “kleptogamy.” “Stolen kisses” has something of the same flavor. So being alpha is only one strategy for males to continue their lines. Being beta or gamma with an inclination for kleptogamy is also a strategy. There are others.

  An unambiguous, well-defined dominance hierarchy minimizes violence. There’s plenty of threat, intimidation, and ritual submission, but not much bodily harm. Violence does occur when the rank order is uncertain or is in a state of flux. When young males attempt to establish their place in the hierarchy, or when there’s a struggle at the top for alpha status, then there can be serious injuries, even death by combat. But if you don’t mind constantly subordinating yourself to those of superior rank, dominance hierarchies provide a peaceful and ritualized environment with few surprises. Perhaps this is part of the appeal for those humans drawn to the religious, academic, political, police, and corporate hierarchies, and the military establishment in peacetime. Whatever inconveniences hierarchy may impose are offset by the resulting social stability. The price may be paid in anxiety—anxiety about offending those of higher rank, being perceived as insufficiently deferential, forgetting yourself, committing lèse-majesté.

  In maintaining the dominance hierarchy, all conflicts (chiefly ritual or symbolic combat) are between animals who know each other well. But xenophobic intraspecific aggression is different, occurring between animals with no perceived bonds, relationships, or even familiarity. It’s an encounter with strange-smelling aliens, and the circumstance most likely to lead to casualties and deaths.

  When an unfamiliar mouse arrives, rats drop what they’re doing and attack it—dominant rats attacking the intruder’s back and frequently mounting it in the process, while subordinate rats attack the intruder’s flanks and rarely mount it. Each in his own way.10 Among mice living in small groups, those at the top of the hierarchy tend to be most active in scuffling, intimidating, and fighting, in reacting to novelty, and in fathering baby mice. They also have sleeker coats than the subordinate males. But when it comes to fighting mice of another group,11 suddenly democratic forms come into play and the subordinates fight side-by-side with the alphas.*

  The simplest geometry of a dominance hierarchy is linear or straight-line. This is what we’ve been describing. The private defers to the corporal, the corporal to the sergeant (and if you look more closely, there are various hyperfine grades of privates, corporals, and sergeants), the sergeant to the second lieutenant, and so on, up through first lieutenant, captain, major, lieutenant colonel, colonel, brigadier general, major general, lieutenant general, plain old general, and general of the army or field marshal. The military establishments of different nations have different names for the various ranks, but the basic idea is the same: Everyone knows his rank. A currency of deference is offered by subordinate to superior. Homage is paid.

  Linear hierarchies are a mode of social organization readily observable in domestic fowl, which is where the phrase “pecking order” originates. It’s especially clear-cut among the hens. (In mammals the pecking order is often the chief fact of male social life.) Again, the alpha hen pecks beta and everybody lower; beta pecks gamma and everybody lower; and so on down the hierarchy to poor omega, who has no one at all to peck. The high-ranking males try to sexually monopolize the hens, but sometimes they fail. Cocks dominate hens except on rare occasions; the word “henpecked” refers to the exceptions and comes from everyday observation of barnyard life.

  With large populations a linear rank order is rare; instead, little triangular loops break out in which delta dominates epsilon, epsilon dominates zeta, but zeta in addition to dominating eta also dominates delta, or maybe even someone higher up the hierarchy.12 This leads to a social complexity that may be opposed by die-hard conservative chickens.

  How does the dominance hierarchy get established? When two chickens are introduced to each other, there is usually a brief squabble—involving much clucking, squawking, pecking, and feathers flying. Or else one chicken takes a good look at the other and submits without a fight, as is usually the case when an immature chicken is confronted by a healthy adult. Among vigorous hens, the winner is the better fighter, or the better bluffer. A home-court advantage is reported: A hen is more likely to win the fight in her own yard than in her adversary’s. Aggressiveness, bravery, and strength play their roles. After a single instance of dominance combat, the relationship between the two hens is often frozen; the higher-rank has the right to peck the lower-rank without fear of retribution. Flocks in which high-ranking hens are regularly removed and replaced by total strangers fight more, eat less, lose weight, and lay fewer eggs. In the long view, the pecking order is in the interest of the chickens.13

  “Playing chicken” is an American male adolescent game of 1950s vintage in which each threatens the other to see who will flinch first. The most familiar example involves automobiles speeding directly toward one another; he who swerves first may gain his life (and, incidentally, save that of his rival) but lose his status. Calling it “playing chicken” recognizes its deep evolutionary origins. Being chicken, in the same youth culture, means being fearful of performing a risky or heroic action. Again, the behavior of subordinates in the barnyard dominance hierarchy is evoked; again, the choice of words betrays if not real knowledge at least a suspicion of the animal roots of the practice.

  Another way in which our awareness of animal dominance hierarchies has insinuated itself into the language and proves useful in describing our own behavior is the use of the phrases “top dog” for the alpha male and “underdog” for everyone else. When we say we’re for the underdog in sports or politics or economics, we’re revealing an awareness of dominance hierarchies, their injustice and their shifting fortunes.

  There are monarchical social systems in which everyone is dominated by the alpha male or the few highest-ranking males, and hardly any aggression occurs in the rest of the group. The dominant male spends a considerable amount of his time calming outraged subordinates and adjudicating disputes. Sometimes justice is a little rough, but often merely a bark or grimace will suffice. In such systems especially, dominance hierarchies carry with them social stability. The males of many species have evolved potent weaponry. Life would be a lot more dangerous if every time two piranha males, or two lions, or two stags, or two elephant bulls had a difference of opinion, it was a fight to the death. The dominance hierarchy—with relative status fixed for considerable periods of time, and the institutionalization of ritualized rather than real combat in settling serious disputes—is a key survival mechanism. Not only is there a genetic advantage for the dominant male, but also for everyone else. Pax dominatoris. Even if you have to take a lot of abuse, even if you sometimes resent the brass, it’s safe, maybe even comfortable, in such a system—where everyone knows his place.

  So what kind of selection is this? Is it simple individual selection for the alpha male, with the benefit for other males being only incidental? Is it kin selection, because the lower-ranking males are not-too-distant relatives of the alpha? Is it group selection, because such a group, structured and stabilized by a dominance hierarchy, is more likely to survive than one in which combat to the death is the norm? Are these categories separable and distinct?

  The alpha might be of a mind to attack an offending inferior, but if the latter makes the species’ characteristic submission gestures, the former feels obliged to spare him. They have not sat down and agreed on a moral code, no tablets have been carried down from the mountain, but the postural and gestural inhibitions to violence work very much like a moral code.

  One of the most spectacular examples of dominance behavior in groups—known among animals as different as birds, antelopes, and (perhaps) midges—is called the lek:

  [L]eks are tournaments, held before and during the breeding season, day after day, when the same group of males meet at a traditional place and take up the same individual positions on an arena, each occupy
ing and defending a small territory or court. Intermittently or continuously they spar with their neighbours one at a time, or display magnificent plumage, or vocal powers, or bizarre gymnastics … Though they have territories, yet they have a hierarchy with the top-ranking males typically placed in the middle and ungraded lesser aspirants ranged outside. Females come to these arenas in due course to be fertilized, and normally they make their way through to one or other of the dominants in the centre.14

  Perhaps spring break at Ft. Lauderdale or Daytona Beach is one of the more conspicuously lekish human institutions.

  Among reptiles, amphibians, and even crustaceans, dominance behavior is common.15 The varanids (such as the komodo dragon) are very good at ritualized and stereotyped intimidation displays. They rattle or lash their tails, rear up on their hind legs, inflate their throats, and, if their rival has not yet submitted, attempt to wrestle him to the ground. In crocodiles, dominance is established by slapping the head into the water, roaring, lunging, chasing, and biting, pretend or real. When interrupted in his mating embrace, a male frog croaks; the deeper his croak, the greater his implied size when disengaged, and the more diffident is the would-be intruder. A toothless, brightly colored Central American frog, genus Dendrobates, intimidates intruders by performing a vigorous sequence of push-ups. But among the skinks, in which aggression is released seasonally when the heads of the males turn bright red, the virtues of intimidation by bluff are often lost sight of, and the two rivals tear into each other without so much as a preliminary throat swelling. When hermit crabs introduce themselves, they devote a few seconds to taking each other’s measure—by stroking one another with their antennae; the smaller then promptly submits to the larger.16 Stalk-eyed flies do the same; the more dominant individuals are the ones with the more widely separated eyes.