February 26, 2014 | 3
Many years ago, while wandering through Amboseli National Park in Kenya, an elephant matriarch named Echo came upon the bones of her former companion Emily. Echo and her family slowed down and began to inspect the remains. They stroked Emily’s skull with their trunks, investigating every crevice; they touched her skeleton gingerly with their padded hind feet; they carried around her tusks. Elephants consistently react this way to other dead elephants, but do not show much interest in deceased rhinos, buffalo or other species. Sometimes elephants will even cover their dead with soil and leaves.
What is going through an elephant’s mind in these moments? We cannot explain their behavior as an instinctual and immediate reaction to a dying or recently perished compatriot. Rather, they seem to understand—even years and years after a friend or relative’s death—that an irreversible change has taken place, that, here on the ground, is an elephant who used to be alive, but no longer is. In other words, elephants grieve.
Such grief is but one of many indications that elephants are exceptionally intelligent, social and empathic creatures. After decades of observing wild elephants—and a series of carefully controlled experiments in the last eight years—scientists now agree that elephants form lifelong kinships, talk to one another with a large vocabulary of rumbles and trumpets and make group decisions; elephants play, mimic their parents and cooperate to solve problems; they use tools, console one another when distressed, and probably have a sense of self (See: The Science Is In: Elephants Are Even Smarter Than We Realized)
All this intellect must emerge, in one way or another, from the elephant brain—the largest of any land animal, three times as big as the human brain with individual neurons that seem to be three to five times the size of human brain cells. Over the course of their evolutionary history, elephants—just like humans—experienced a dramatic increase in their encephalization quotient (EQ): the ratio between the actual mass of an animal’s brain and what you would expect its brain mass to be based on its overall body size. An EQ of 1 is exactly what you would expect. A higher EQ generally but not always syncs up with what we perceive as greater intelligence. Humans have an EQ higher than 7; dolphins between 4 and 5; orcas and chimpanzees between 2 and 3. As far as we can tell, elephants did not start out particularly bright. The African bush and forest elephants, the Asian elephant and their extinct cousins the mammoths all evolved in Africa many millions of years ago. Some of the most ancient relatives of elephants were swamp-wallowing creatures akin to hippopotamuses and tapirs with flexible upper lips and as many as eight short tusks. Over time elephants became larger and larger, evolving to survive by eating huge amounts of relatively nutrient poor grasses. As their bodies grew, so did their brains—even more than one would predict. Between 35 million years ago and today, the EQ of Proboscidea—the taxonomic family containing modern elephants and their extinct relatives—increased 10 fold, from 0.2 to greater than 2 for Asian elephants.
Scientists have only started to seriously examine the neural architecture housed in the elephant cranium, but they have already found some unique features. Paul Manger of the University of Witwatersrand moved to South Africa in 2002 for the express purpose of studying the elephant brain. What stands out so far, he says, are neural networks specialized for the elephant’s extraordinary senses and kinetic talents.
At the annual Society for Neuroscience meeting in San Diego, California this past November, Manger, Suzana Herculano-Houzel of the Instituto de Ciências Biomé́dicas/Federal University of Rio de Janeiro, Brazil and their colleagues presented the first accurate cell count for a whole elephant brain. Herculano-Houzel has developed one of the most sophisticated methods for counting the number of cells in a brain. Basically, she liquefies entire brains, preserving only the nuclei—sacs of DNA that serve as the command center of cells. Then she tags the DNA inside each nucleus with fluorescent proteins and measures the intensity of the fluorescence to get the total number of nuclei. Since each cell has only one nucleus, that number is the number of total brain cells.
It turns out the elephant brain has three times more neurons than our own: 257 billion to our 86 billion. The vast majority of these neurons are found not in the cerebral cortex—the seat of abstract thinking in humans—but rather in the elephant’s cerebellum, which controls breathing, heart rate and movement, among other duties. The elephant cerebellum has 250 billion neurons; its cortex has 5.5 billion. Humans have about 70 billion neurons in the cerebellum and 16 billion in the cortex.
Manger and Herculano-Houzel suspect that the elephant depends on such a dense cerebellum to maneuver one of the most sensitive and versatile appendages in the animal kingdom. With more than 100,000 distinct bundles of muscle fibers, an elephant’s prehensile trunk is just as dexterous as a human or chimpanzee’s hands. In the first few months of life, as a baby elephant learns to handle its trunk, the wriggling appendage seems to have a mind of its own—reminiscent of a human infant’s flailing limbs. By adulthood, elephants can use their trunks to snorkel when submerged, heave objects weighing more than 700 pounds, or gingerly crack open a peanut shell.
Neural networks in the temporal lobe devoted to vocal communication and hearing are also particularly large and complex in the elephant brain. Elephants can chirp softly or trumpet about as loudly as a jet taking off. They can recognize the calls of up to 100 different elephants even from a distance of nearly 5,000 feet. And they often communicate with low-frequency rumbles that humans cannot hear unaided. Some scientists have speculated that thirsty elephants guide themselves towards distant rainfall by detecting vibrations produced by thunderstorms. Along with sound and touch, elephants primarily rely on odor to learn about one another and the world around them. A fusion of the upper lip and nostrils, the trunk gives elephants a sense of smell that is even more acute than that of nosy critters like rodents and dogs. One region of the elephant olfactory bulb—the part of the brain that processes smell—contains extra layers of cells in a honeycomb arrangement not found in other mammals.
If the elephant’s gargantuan cerebellum—as well as its intricate olfactory and temporal lobes—equip the creature with sensory superpowers, what features of the elephant brain account for its more sophisticated, more abstract mental talents: for its cooperative problem-solving, understanding of death and self-awareness? Based on what we know about brains generally, this type of intellect arises from the cerebral cortex. Manger and Herculano-Houzel’s recent investigations confirmed, however, that despite having a brain three times as large as our own, the elephant’s cerebral cortex contains surprisingly few neurons and is nowhere near as dense as the human or chimpanzee cortex. Yet the elephant is clearly capable of astounding intelligence.
Benjamin Hart of the University of California Davis has speculated that the elephant cortex derives its intellectual prowess not from local density but from widespread interconnectivity. He suspects that, whereas the human and chimpanzee brains have evolved many tight-knit networks of nearby neurons throughout the cortex—akin to states packed with highly populous cities—the elephant brain has favored lengthy connections between far-flung brain areas, building the equivalent of an extensive cross-country railroad system. For now, though, this is mostly hypothetical.
To look an elephant in the face is to gaze upon genius. Here is a creature who experiences emotional intimacy with friends and family, who seems to understand death and treats its dead in a way that borders on ceremonial. Here is an animal who can recognize itself in the mirror, fashion twigs into tools, formulate and implement plans, and remember someone’s face for decades. An animal that has exquisite ways of sensing the world we can never experience firsthand and a complex language we will probably never decipher. An animal whose cleverness parallels our own, yet is in many ways unique. As a species, we have long valued our extraordinary mental powers, obsessively comparing our intelligence to the braininess of all other beasts. We insist on continually updating a grand hierarchy of cleverness. The more one learns about exceptionally smart and sensitive animals like the elephant, however, the less useful such rankings become. It suddenly seems silly to think of intelligence as a pyramid. Yes, some creatures have bigger brains and some are capable of impressive mental feats others will never achieve. But what is far more impressive—what is far more fascinating—is the glorious diversity of intelligence on our planet. There are so many different ways to be smart. Every species alive today is exactly as smart as its survival required. When we look into the eyes of the elephant, we should recognize nothing less than an intellectual equal.