The Dolphin in the Mirror

by Diana Reiss

  Another measure of intelligence and brain complexity is based on the amount of cortical folding. If you have an eight-by-eleven-inch sheet of paper and want to fit it into your closed fist, you would scrunch it up, causing the paper to crease and fold in on itself. This scrunching (to use a technical term) allows increased surface area within the same small volume. So a greater degree of cortical folding, or convolutions, represents more surface area, and with increased surface area, one can get a much larger number of brain cells into the brain without changing its volume. This is important because the total number of brain cells, or neurons, may also be a factor in intelligence. The part of the brain that is convoluted is called the cerebral cortex, that part of the mammalian brain associated with higher cognitive processes and thinking. Our brains are more convoluted than those of our primate relatives. Only one brain is known to be more heavily convoluted than ours. Again, it's the dolphin brain.

  Recent comparisons of different measures such as brain size and relative brain size have led some scientists to conclude that the average number of neurons in the brain may correlate better with intelligence when making comparisons across species.9 Recently Suzana Herculano-Houzel and her colleagues used a novel technique they developed to count neurons in the human brain and in those of other species. They estimated that the human brain has approximately eighty to ninety billion neurons; the great ape brain has approximately twenty-four to thirty-two billion neurons; the elephant has around twenty-three billion neurons; and the false killer whale has about thirty-two billion neurons. No data for dolphins are in as of yet, and it will be interesting to see how they compare using this measure.

  But an additional factor to consider is the size of the neurons themselves in different brains. Our neurons and those of other primates are smaller than those found in the brains of dolphins, whales, elephants, and rodents, and therefore more brain cells can fit into a given space in the human and primate brains. It has been suggested that there are two different scaling schemas: a primate scheme, with smaller neurons but more of them, and a rodent scheme, also found in dolphins, whales, and elephants, in which there are larger neurons but fewer of them. These may represent two different architectural strategies for building a brain.

  Even neural numbers and brain size together may not provide the whole picture. For example, insects with very small brains learn and perform complex behaviors with a very limited number of neurons. This suggests that computational power may depend not only on the size but also on the organization of the brain—the way in which the neurons are connected. Even the specific types of cells found in brains may provide clues about intelligence. Von Economo neurons (VENs) are specialized, elongated spindle-shaped cells that are found in specific parts of the human brain and are thought by some to be linked to social cognition, empathy, emotion, theory of mind, and "gut" feelings.10 Patrick Hof at Mt. Sinai Medical School and Stuart Allman at Caltech and their colleagues have discovered VENs in specific regions in the brains of humans, great apes, elephants, and cetaceans—those species showing complex social and cognitive abilities, including the capacity for self-awareness (as indicated by mirror self-recognition) and empathy.

  Taken as a whole, we can no longer rest on the assumption that the human brain is unique and superior to those of other animals based on its absolute or relative size, the size of the cerebral cortex, or its degree of convolutedness. This is certainly not to suggest that the human brain is not exquisite in its capabilities. Instead, it helps us to realize and appreciate that other brains, other minds, have evolved in parallel to meet complex social and environmental challenges. Other exquisite minds may exist as well. Social minds, self-aware minds, sentient minds in the seas.

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  Metabolically, the brain is a very expensive organ to maintain. In an adult human, the three pounds of gray and other neural matter in the head represents less than 2 percent of total body weight, yet it consumes about 18 percent of the body's energy budget. And building a large brain in the womb is a burden for the gestating mother. Large-brained species can sustain their elevated cognitive status only if they have diets rich in energy. Nature is a very conservative mistress, and she maintains energy-expensive organs and behaviors only if there is some selective advantage for doing so. If a species is burdened with the exceptional energy demands of a large brain, then being brainy must therefore have exceptional benefits. The question then is, Why do dolphins need to be as smart as they are? That is, what are the benefits of having a powerful mind in the waters?

  Let us step back a minute and think about our own cognitive endowment. We live in a world where our fellow humans write computer code and symphonies, smash atoms and think about weird quantum worlds, create wondrous pieces of theater, art, and architecture, and imagine florid fantasies such as The Hitchhiker's Guide to the Galaxy. And yet the brains that accomplish these remarkable feats of creative intelligence are the same brains that evolved to meet the cognitive demands of a nomadic, small-band, hunting-and-gathering lifestyle in the Paleolithic period, more than a hundred thousand years ago. The men and women back then had the same type of brain as the average university professor today, and yet they spent their lives stalking and killing antelope and other such game, collecting berries, and digging up tubers.

  In his book Mind from Matter, Max Delbruck, a Nobel laureate in physics and an early molecular geneticist, discussed our large human brains and wondered why so "much more was delivered than was ordered."

  We can ask the same kind of thing about dolphins. As we know now, they have the ability to learn arbitrary symbols and use them appropriately in relation to specific objects. Being able to respond appropriately to arbitrary hand gestures and being sensitive to "word" order, as dolphins are in Lou Herman's facility in Hawaii, is of the same intellectual level (see next chapter). The dolphin literature is full of instances where these animals perform tasks that require not only motivation and attention but also complex problem solving and creative intelligence.

  These experimental activities have something unusual in common: they are carried out under circumstances that are, cognitively speaking, completely foreign to dolphins' daily lives. Dolphins show us that they can operate with great skill when faced with intellectual challenges that are alien to a dolphin's life in the ocean. Yet they handle such arbitrary and abstract concepts and tasks with ease. Pan and Delphi and others in my research lab, and Akeakamai and Phoenix and other dolphins in Lou Herman's lab, performed tasks that appeared to be different than anything their natural environment might have prepared them for. How come they could do these things?

  How come humans and dolphins have brain capacities that appear to exceed the daily exigencies under which they evolved? And chimpanzees, and perhaps elephants too, for that matter? If we put the question in the terms of evolutionary biology, it becomes: What selective advantage does a high degree of intelligence confer on humans, dolphins, chimpanzees, and elephants in their state of nature?

  We have long been obsessed with the forces that drove the big human brain along its evolutionary path. Language has often been mentioned as contributing to the large cerebral cortex—but there is little evidence that language centers in the brain account for an unusually large fraction of brain mass. In all probability, brain expansion in the early human lineage began long before spoken, referential language came into wide use. Human brain expansion was under way by about two and a half million years ago, around the same time that stone tools started to appear in the archaeological record. (Earlier than that, the brains of our human ancestors were pretty much apelike in size.) In the 1950s, Man the Toolmaker11 became a popular model to explain the increase in brain size in early human evolution. A decade later, this model was replaced by Man the Hunter,12 as anthropologists became fascinated with technologically primitive societies and what they could tell us about how our ancestors might have lived. (Both of these models are very much male oriented, of course: Man the [Something Macho]. Some balance was restor
ed when an alternative, Woman the Gatherer, was offered in the mid-1970s.*,13)

  Whatever their separate merits, both of these models focused on the world of practical affairs, of subsistence, as the evolutionary engine of brain expansion. Yet at about the same time that the Woman the Gatherer model was attracting a lot of interest, an important shift of emphasis began to take place, propelled by the paradox I outlined above: in laboratory situations, chimpanzees appear to be too smart for their own good. "Some primate species (and mankind in particular) are much cleverer than they need be," Nicholas Humphrey, a psychologist at Cambridge University, wrote in a now classic paper called "The Social Function of Intellect,"14 published in 1976.* Surprising as it may seem, until this point biologists had not given much thought to how intellect might contribute to biological fitness; that is, success in producing offspring. Humphrey was promulgating a shift in perspective from the world of practical affairs to the world of social affairs and the intellectual demands of managing relationships in complex societies.

  When biologists did address the function of intellect, or creative intelligence, it was mainly in the context of making and doing things. For humans, this included inventing new tools and finding new ways to use existing tools in order to make better use of environmental resources. Although Jane Goodall discovered in 1960 that chimpanzees also make and use tools, for them it is an extremely limited activity. Great apes are hardly simian handymen! Nor are they especially energetic or inventive when it comes to gathering their daily vittles, as Humphrey observed:

  "The great apes, demonstrably the most intellectually gifted of all animals,† seem on the whole to lead comparatively undemanding lives, less demanding not only of those of lower primates but also of many non-primate species. During the two months I spent watching gorillas in the Virunga Mountains I could not help being struck by the fact that of all the animals of the forest the gorillas seemed to lead much the simplest existence—food abundant and easy to harvest (provided they knew where to find it,) few if any predators (provided they knew how to avoid them) ... little to do in fact (and little done) but eat, sleep, and play. And the same is arguably true of natural man."15

  While the world of subsistence for the great apes is relatively undemanding and predictable, the world of interpersonal interaction in complex social systems is anything but. And this was the nub of Humphrey's insight: "I propose that the chief role of creative intelligence is to hold society together,"16 he wrote. The overall structure of chimpanzee society is known as fission-fusion, which means that from time to time small groups come together to form a larger group that eventually splits apart into the original subgroups, with some change in group membership occasionally taking place. Mothers and offspring (females and younger males) are at the center of chimpanzee society; older juveniles form their own groups; and older males are sometimes solitary and sometimes band together for hunts or even attacks on neighboring groups. When young males reach maturity, they leave to find another group, where they spend a lot of social skills being accepted as members.

  The organizing principle of chimpanzee society, indeed of all animal societies, is reproductive success. Males attempt to sire as many offspring as they can, while the females' goal is to be courted by the most genetically desirable males. In most animal societies, the outcome of a challenge by one male to another (for access to females) is rather predictable. The winner is the bigger male, or the one with longer canines, or the bigger antlers (or whatever weapon of male-to-male combat is appropriate). Not so for chimps, baboons, and other large monkeys. Although physical prowess is helpful in these higher primates, an individual male's ability to form friendships or alliances with other individuals, both male and female, is key to reproductive success. A weakling male can sometimes mate with a desired female, provided he times his amorous advances well and moves in when his friends are at hand to help him fend off a challenge by a more dominant male or when the other male's allies are not around to intervene.

  Being socially adept in a complex social group therefore requires remembering who is related to whom, which individuals have recently formed an alliance, whom you have helped recently and therefore might expect help from when the need arises, and so on. The intellectual challenge is made greater by the constant shifting of alliances, as other individuals in the group change their allegiances, in hopes of greater advantage. A shift in allegiance by a single individual might subtly change the balance of power, causing further changes to cascade throughout the group.

  Every individual, in order to maximize his or her reproductive success, is constantly calculating and recalculating the balance of power in the group among older and younger uncles and aunts, nieces and nephews, and unrelated individuals too. It's a very complicated game with a constantly changing set of rules.

  These multigenerational groups provide protection and an environment in which the young can learn subsistence and parenting skills. Yet the social challenges were novel in the world of nature when they arose in higher primates. "It asks for a level of intelligence which is, I submit, unparalleled in any other sphere of living,"17 wrote Humphrey. With the evolution of higher-primate societies, individuals had to become what Humphrey called "nature's psychologists." And once social skills become an effective element in the equation of reproductive success, a feedback loop arose:

  "If intellectual prowess is correlated with social success, and if social success means high biological fitness, then any heritable trait which increases the ability of an individual to outwit his fellows will soon spread through the gene pool. And in these circumstances there can be no going back: an evolutionary ‘ratchet' has been set up, acting like a self-winding watch to increase the general intellectual standing of the species."18

  Nature's psychologists need to be more intellectually gifted than creatures whose social environment is less complex. Humphrey called this the social intelligence hypothesis* and used it to explain the evolution of big brains relative to body size. This line of reasoning quickly became popular (and still is), and was co-opted in a way by Richard Byrne and Andrew Whiten, primatologists at the University of St. Andrews; they preferred the phrase the Machiavellian intelligence hypothesis. Niccolû Machiavelli (1469–1527) was an Italian philosopher whose most famous work, The Prince, instructs the reader in the ways of social and political success through clever manipulation of relationships and alliances. Many people, myself included, believe the phrase Machiavellian intelligence sounds unnecessarily negative. I prefer the term social intelligence or social cognition—the skills are related to attraction and cooperation, not just competition.

  Humans, like chimps, live in a fission-fusion society. So do bonobos (pygmy chimpanzees), several other primate species, and many nonprimates, such as lions, deer, and even some fish. The dolphins' social organization is also fission-fusion.

  Dolphins form close and long-lasting bonds with one another that can last lifetimes, and they often interact collaboratively and cooperatively in alliances in their myriad of foraging strategies, in mating, and in the rearing of young. Alliances can last from minutes to hours or can be long-term relationships. For example, three male dolphins may spend the majority of their time together swimming and finding food in what is called a first-order alliance. At times they may rejoin their larger social group or mix and mingle with other individuals in other alliances and form new, more temporary alliances. Related or unrelated females with young calves form another type of alliance and spend time together in subgroups collectively caring for their offspring. Dolphin mothers, like human mothers, seem to have to learn about parenting skills, and depending on their knowledge and disposition, they show varying degrees of vigilance toward their youngsters. I have observed a wide range of mothering skills and styles over the years. Females will often allomother—baby-sit and care for another's calf, allowing the real mom to forage or rest a bit. Dolphins can spontaneously begin to lactate and, like wet nurses, provide needed nourishment for an orphaned calf.

/>   Richard Conner and his colleagues have reported that bottlenose dolphins living in Shark Bay, Australia, form multiple-level male alliances within a social network; they suggest that this level of alliance complexity has been found previously only in human societies.19 If you're a male dolphin living in Shark Bay, you may cooperatively herd females with the one or two members of your first-order alliance—your closest buddies. But you may also join up with another alliance to form a larger second-order alliance, or even meet up with other alliances to form a multiple alliance of males that cooperatively work together to compete with other multiple alliances of males in herding and guarding females with whom they hope to mate. Alliance formation and cooperative behavior is considered a hallmark of social complexity and requires sophisticated social cognition.*

  Where does self-awareness, or consciousness, fit into this hypothesis? Are nature's psychologists really just automatons, animals with "clever brains, but blank minds"?20 Or are they creatures that are aware of their actions and feelings, conscious of themselves in the world? Does self-awareness make a more effective social individual? Many of these ideas are showing up in studies of consciousness, an area that until recently was avoided by neuroscientists because it seemed too difficult to quantify and experiment with. This is changing.