The World in Six Songs: How the Musical Brain Created Human Nature (32 page)
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Authors: Daniel J. Levitin
BOOK: The World in Six Songs: How the Musical Brain Created Human Nature
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I said earlier that I believe development and mutations in the prefrontal cortex created the brain structures that underpin the musical brain, which in turn allowed for the type of mental structures that were required in order for us to develop societies. Although the sense of hearing is shared across all vertebrates, separate changes in brain structure allowed many species to use the sense of hearing for communication with one another. Vocalizations, whether the croaking of frogs, the chirping of birds, or the pan-hoots of chimpanzees, served to signal physical and emotional states among members of a species, who developed brain mechanisms to both produce and interpret those signals. Of course, there is a risk in making any sound, because predators can more easily locate the sound maker; the evolutionary advantages of being able to communicate through sound had to outweigh the disadvantage of attracting predators.
Vocalization facilitates the process of sharing information, in turn enhancing survival. There is a very high correlation between the amount of vocalization and the closeness of social relationships in a species. In particular, pair-living species tend to vocalize more to attract mates, enhance pair-bonding, defend their families’ territory and resources, and locate one another (especially in the dark or around corners or other visual barriers). In birds, 90 percent of the species live in pairs, and birds of course are famous for their vocal behaviors. In pair-living primates, like the siamang gibbon, owl monkey, and titi monkey, vocalization is a conspicuous feature.
During a typical day, chimpanzees—our closest relatives—associate in temporary parties that vary in size and membership, much as humans do. They may become separated from friends and family and have a strong need to be assured of future meetings and cooperating. Sound communication gives this reassurance. Because primatologists can identify an individual chimp by its call, we assume other chimps can too. Thus, rudimentary vocal communication may have developed as part of the increasingly complex social lives that primates lived.
As they left the cover of trees out on the savannah, protohumans exposed themselves to increased danger from predators. They needed greater brain power to help them to stay one step ahead of those predators and to deal with the wide range of environmental variation that came from their nomadic lifestyle. Diet plays a surprising part in the brain size story too, as biologists have found an inverse relationship between brain size and digestive tract size (which in turn is inversely related to food complexity). Those primates who eat leaves tend to have smaller brains but larger digestive tracts than those who eat fruit. The reason is that leaves are more difficult to digest than fruit, requiring more processing stages and more energy to break down the complex carbohydrates into usable sugars.
On the other hand, fruit-eating requires more cognitive skill, specifically the ability to remember the location of fruit-bearing trees, anticipate when they will be in season, and discern ripe from unripe (or rotten) fruit. This latter process benefits from improved color vision—the color of a fruit’s skin carries information about how ripe it is, and therefore the nutritional content and digestibility of the fruit—all which require increased brain size in the occipital cortex. The total amount of energy available to an organism is limited, forcing an evolutionary trade-off between brain size and digestive tract size. Geneticists have found that humans have lost an ability possessed by most mammals to create vitamin C internally; the gene for L-gulonolactone oxidase (GULO) on chromosome 8 is nonfunctioning (defective) in humans and other primates, and this is believed to be a result of our becoming fruit eaters some 40 million years ago. Because vitamin C was available exogenously, we and our primate cousins didn’t need to manufacture it anymore, and so the ability was lost through genetic drift. This is another example of Deacon’s notion of parsimony: Evolution often “offloads” instructions or survival plans from the genome to the environment.
There are relatively few species with big brains like ours, and this is because big brains carry with them a high biological price tag: They are metabolically expensive in terms of the energy needed to furnish them with oxygen, to cool and to protect them. Complex brains take longer to mature and to train, and large-brained animals are correspondingly more dependent on their parents or caregivers and for a longer time. This means extra energy from parents, which in turn means fewer offspring, fewer opportunities for a parent to successfully pass on his or her genes to all of posterity. All these high costs must be outweighed by the benefits (or evolution would not have selected them), but the cost-benefit ratios are unlikely to be the same across species.
Our brains are not only large for our body size, but the prefrontal cortex, seat of the musical brain, is large compared to the rest of our brains. This region—just behind your forehead—is most highly developed in humans and tends to be largest in those species that are most social, for example chimpanzees, bonobos, and baboons. Well-connected female baboons have more babies who receive better care as the community chips in to help these well-liked, high-status females. Baboon social order, as represented in the prefrontal cortex, has an evolutionary basis.
When people think about other people, it is the prefrontal cortex that is activated. The connection between social behavior, communication, and the prefrontal cortex is strengthed by the fact that the cortex developed independently in a completely different biological order,
Carnivora.
As the zoologist Kay Holekamp recently discovered, the spotted hyena—an especially social mammal—also has an enlarged prefrontal cortex. “Spotted hyenas live in a society just as large and complex as a baboon’s,” she says. Because hyenas and primates last shared a common ancestor 100 million years ago, we infer that similar evolutionary forces worked independently to arrive at a similar adaptive solution: the prefrontal cortex as the seat of sociability. In humans, it evolved further to become the seat of music, language, science, art, and ultimately—society.
Carnivora.
As the zoologist Kay Holekamp recently discovered, the spotted hyena—an especially social mammal—also has an enlarged prefrontal cortex. “Spotted hyenas live in a society just as large and complex as a baboon’s,” she says. Because hyenas and primates last shared a common ancestor 100 million years ago, we infer that similar evolutionary forces worked independently to arrive at a similar adaptive solution: the prefrontal cortex as the seat of sociability. In humans, it evolved further to become the seat of music, language, science, art, and ultimately—society.
Clearly there are advantages to having the kind of brain we humans do, with enlarged, highly developed, intricately connected prefrontal cortices. So, you might ask, if that big prefrontal cortex is so useful, why don’t
all
animals have one? But evolution doesn’t work that way. We might just as well ask why humans don’t all have long giraffe-like necks, and fishlike gills, and night vision like owls. Evolution selects adaptations that solve specific problems (and it has to build on existing structures). Each adaptation comes with certain metabolic costs, and only pervades the population when its advantages outweigh those costs. The
handiness
of being able to avoid using ladders or breathing underwater simply isn’t the same as a biological necessity; convenience is an inadequate motivation for natural selection. We have big brains because they solved a specific problem. Typically such a solution is required when there is competition for food resources, or a need to escape environmental or predatory dangers.
all
animals have one? But evolution doesn’t work that way. We might just as well ask why humans don’t all have long giraffe-like necks, and fishlike gills, and night vision like owls. Evolution selects adaptations that solve specific problems (and it has to build on existing structures). Each adaptation comes with certain metabolic costs, and only pervades the population when its advantages outweigh those costs. The
handiness
of being able to avoid using ladders or breathing underwater simply isn’t the same as a biological necessity; convenience is an inadequate motivation for natural selection. We have big brains because they solved a specific problem. Typically such a solution is required when there is competition for food resources, or a need to escape environmental or predatory dangers.
Chief among these benefits would have been a greater ability to adapt to environments and to shape parts of the environment to meet our needs. Tool use is one important milestone in cognitive evolution. Archaeologists—especially cognitively oriented ones who are interested in the evolution of mind—talk a lot about stone tools, sharp flakes chipped from parent “cores,” found in some early human excavation sites. Why all the fuss about some old rocks? It’s because tool
making
as opposed to mere tool
use
(which crows and monkeys do) represented a major cognitive leap: It required a type of thought not before seen in any other species. These stone tools were the first implements that conformed to a “mental template,” an
idea
in the mind of the beholder that existed prior to the completion of the tool. Stone tools are thus the first evidence we have of the birth of
symbolic thought,
a qualitative change in ability, one that distinguishes humans from other species and makes possible art and music.
making
as opposed to mere tool
use
(which crows and monkeys do) represented a major cognitive leap: It required a type of thought not before seen in any other species. These stone tools were the first implements that conformed to a “mental template,” an
idea
in the mind of the beholder that existed prior to the completion of the tool. Stone tools are thus the first evidence we have of the birth of
symbolic thought,
a qualitative change in ability, one that distinguishes humans from other species and makes possible art and music.
Archaeologist Nicholas Conard discovered a mammoth tusk from the Ice Age—about 37,000 years ago—at a dig in southern Germany. Its existence suggests that humans must have brought musical instruments with them when they left Africa for Europe. The tusk had been split down the middle, hollowed out, and had holes made in it to turn it into a flute—all this would have required a great deal of craftsmanship, time, effort, and most importantly, a mental template of what the finished artifact needed to look like. As Ian Cross notes, “One of the most technologically advanced tools of the time was a musical instrument!”
The earliest known
Homo sapiens
fossils in Europe date to about 40,000 years ago. These European ancestors migrated from Africa and possessed not only the ability to fashion stone tools, but workmanship that displayed what the anthropologist Ian Tattersall described as “an exquisite sensitivity to the properties” of these materials. They brought with them carvings, engravings, and cave paintings; they kept their own history on bone and stone plaques; and they made music on flutes that they built from wood and bone. In short, migratory, preindustrial humans of 40,000 years ago had art and an artistic sensibility. “Clearly,” Tattersall writes, “these people were
us.
” The artistic remnants that have been left behind—carvings and paintings—show such sophistication and power that it is likely that they were not our ancestors’ first attempts at art. Rather, they are the lucky ones that survived, and there clearly must have been a great number of refinements and improvements that led to these. Art, in other words, must have existed for tens of thousands of years
before
the earliest artifacts we’ve found.
Homo sapiens
fossils in Europe date to about 40,000 years ago. These European ancestors migrated from Africa and possessed not only the ability to fashion stone tools, but workmanship that displayed what the anthropologist Ian Tattersall described as “an exquisite sensitivity to the properties” of these materials. They brought with them carvings, engravings, and cave paintings; they kept their own history on bone and stone plaques; and they made music on flutes that they built from wood and bone. In short, migratory, preindustrial humans of 40,000 years ago had art and an artistic sensibility. “Clearly,” Tattersall writes, “these people were
us.
” The artistic remnants that have been left behind—carvings and paintings—show such sophistication and power that it is likely that they were not our ancestors’ first attempts at art. Rather, they are the lucky ones that survived, and there clearly must have been a great number of refinements and improvements that led to these. Art, in other words, must have existed for tens of thousands of years
before
the earliest artifacts we’ve found.
The three cognitive components of the musical brain are perspective-taking, representation, and rearrangement. Perspective-taking encompasses the ability to think about our own thoughts (what some call metacognition or self-consciousness). That is, the ability to examine the contents of our own minds, hold them up to the light of day, to the light of reason and objectivity. It also entails recognizing that others have beliefs, intentions, desires, knowledge, and feelings that may be very different from our own.
I
may be feeling happy right now, but that doesn’t mean that
you
are; I may know where the food is hidden and you may not. I sing a song to tell you what I am experiencing, as a way of bridging the separation of our minds, because I know that you do not necessarily experience what I do.
I
may be feeling happy right now, but that doesn’t mean that
you
are; I may know where the food is hidden and you may not. I sing a song to tell you what I am experiencing, as a way of bridging the separation of our minds, because I know that you do not necessarily experience what I do.
Representation is a cognitive operation that allows for displacement in time and space—thinking about things that aren’t there now. I can talk about fear without becoming afraid; I can sing about sorrow that I don’t necessarily feel right now. I can represent love with a ♥ or an arbitrary string of vocal utterances such as “luv,” “amoor,” or “aijou.” Such symbolic representations constitute abstractions, and lay the foundation for the creation of visual (and other) art.
Rearrangement is an ability to combine and recombine objects in different ways, to organize them in theoretically motivated hierarchies, categories, to impose structure on objects based on shifting notions of their content. For example, given a list of words—
banana, baseball, grape, golf—
you could organize them into two groups, fruits versus sports. Or into two other groups, words that begin with
b
versus words that begin with
g
. Or three groups based on the number of syllables each word has. Rearrangement requires computational structures in the prefrontal cortex that other animals may have, but that only humans have learned to fully exploit. The three of these (perspective-taking, representation, and rearrangement) may have evolved independently, but together they are the foundations of the musical/artistic brain.
banana, baseball, grape, golf—
you could organize them into two groups, fruits versus sports. Or into two other groups, words that begin with
b
versus words that begin with
g
. Or three groups based on the number of syllables each word has. Rearrangement requires computational structures in the prefrontal cortex that other animals may have, but that only humans have learned to fully exploit. The three of these (perspective-taking, representation, and rearrangement) may have evolved independently, but together they are the foundations of the musical/artistic brain.
A number of distinct cognitive operations are necessary for the creation of art. Specifically, one needs to (1) form a mental image of the thing to be created; (2) hold that mental image in mind; (3) understand how to go about manipulating objects in the physical world in order to conform to the mental image; (4) compare the ongoing development of physical-world object with the mental image in real time; (5) update plans as necessary to accommodate unforeseen difficulties or mistakes in manipulating the physical object. As the old joke goes, to sculpt a bear you just start with a piece of rock and chip away everything that doesn’t look like a bear.
But of course this is not trivial. Our cave ancestor might have tried to draw a bear with a piece of coal on a wall. First, he needed to understand that the drawing can never look exactly like the thing it represents—it is a
version,
an
abstraction,
of the real thing, an imperfect
approximation
of a mental image. That way of thinking requires the objectivity of perspective-taking—the ability to think about one’s own thought process, one’s limitations, one’s relationship with the world. The artist needed to decide how to draw in a way that preserved essential, recognizable details. This selection process requires abstract (or symbolic) thought. Having drawn a few lines, he would have had to assess the creation objectively: Does this look like I
thought
it would when I started drawing it? This requires an iterative process, changing some aspects of the physical drawing to match the mental image. Finally he needed to ask himself: If someone else were to look at it, would
they
know it was a bear? This also requires the objectivity of perspective-taking, specifically the ability to recognize that other people have their own knowledge, thoughts, and beliefs that are not necessarily the same as our own.
version,
an
abstraction,
of the real thing, an imperfect
approximation
of a mental image. That way of thinking requires the objectivity of perspective-taking—the ability to think about one’s own thought process, one’s limitations, one’s relationship with the world. The artist needed to decide how to draw in a way that preserved essential, recognizable details. This selection process requires abstract (or symbolic) thought. Having drawn a few lines, he would have had to assess the creation objectively: Does this look like I
thought
it would when I started drawing it? This requires an iterative process, changing some aspects of the physical drawing to match the mental image. Finally he needed to ask himself: If someone else were to look at it, would
they
know it was a bear? This also requires the objectivity of perspective-taking, specifically the ability to recognize that other people have their own knowledge, thoughts, and beliefs that are not necessarily the same as our own.
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