3 Policy as a Branch of Biology

The challenge for Niko Tinbergen, Konrad Lorenz, and Karl von Frisch during the middle of the twentieth century was to show that ethology is a branch of biology—in other words, that behaviors evolve in much the same way as other traits. By the time they were awarded the Nobel Prize in Medicine in 1973, their mission had largely been accomplished—not only by their own efforts, but by many others employing a fully rounded four-question approach. Moreover, the historically separate fields of evolution, ecology, and behavior were becoming fused into a single discipline, often labeled by the acronym EEB, which was part of my training as a graduate student.

The challenge of this book is to show that policy is a branch of biology. A standard definition of policy is “a course or principle of action adopted or proposed by a government, group, or individual.” Liberal and conservative politicians propose different policies to improve the economy. Many religions encourage the policy of “do unto others,” at least in some situations. A “tiger mom” might adopt a policy of strict discipline toward her children. To view policy as a branch of biology means that our proposed actions must be deeply informed by evolution. Around the world, we should be consulting evolutionary theory at least as much as we consult our constitutions, political ideologies, sacred texts, and personal philosophies.

This is a radical claim, insofar as an evolutionary worldview is currently absent from virtually the entire policymaking universe. Nevertheless, I hope that it will make sense to you by the end of this book, in the same way that the claim of Tinbergen & Company made sense to the scientific community. In this chapter we will proceed on our journey with three stories that I have arranged in this order for a purpose. The first story describes why so many of us must wear glasses or contact lenses to see clearly. The second story describes how our immune system, an adaptation with a 500-million-year-old history within the vertebrate lineage, can go haywire in modern environments. The third story is about child development. All three stories highlight the importance of Tinbergen’s development question and the concept of evolutionary mismatch, whereby adaptations to past environments can tragically misfire in current environments.

AS PLAIN AS THE GLASSES ON YOUR FACE

Our eyes are a perfect example of a functionally designed object. They capture images of the world in much the same way as a camera, complete with a lens, a photo-sensitive surface, and mechanisms for adjusting the amount of light and focal distance.

Nobody doubts that eyes are designed for seeing. Since eyes were not designed by people, they signify either the existence of another designing agent, such as a god, or a designing process, such as natural selection. That debate was settled long ago within the scientific community. In fact, what we know about eyes today is like a grand version of Richard Lenski’s experiment on E. coli. Just as each of his twelve populations responded independently to the same selection pressure (the ability to use glucose as an energy source), over a hundred animal lineages responded independently to the selection pressure of using light as a source of information.1 One of the most recent discoveries is a single-celled marine organism called Warnowia. While many single-celled organisms have evolved eyespots for orienting toward light, Warnowia has evolved a full-fledged eye with a cornea, lens, and retinal body constructed from subcellular components.2

Just as there are a limited number of ways that glucose can be processed as an energy source by E. coli, there are a limited number of ways that light can be processed as information—but the particular mechanism employed by any particular animal lineage is largely a matter of chance and its previous history. A famous example is the eye of the octopus and other cephalopods, which bears an uncanny resemblance to the vertebrate eye. A closer look reveals differences, however. The octopus eye develops from skin tissue while the vertebrate eye develops from brain tissue. Light strikes the retinal cells of octopus eyes directly but must pass through a layer of nerves and blood vessels to strike the retinal cells of vertebrates. Vertebrate and cephalopod eyes are different because they evolved independently from each other (Tinbergen’s history question), and they are similar because they must have certain anatomical structures to function as eyes (Tinbergen’s function question). All examples of convergent evolution share this combination of similarities and differences.

When we focus on Tinbergen’s mechanism and development questions, eyes are created by a purely physical process, like the formation of a snowflake. A physical process that has not been shaped by selection tends to be variable in its outcome. Snowflakes are an extreme example in which every snowflake’s encounter with its environment turns it into a unique individual. That kind of variability would be disastrous for eyes. Eons of natural selection have shaped the physical process of eye development to result in the same complex organ time after time. How is this miracle of quality control accomplished?3

All examples of convergent evolution share a combination of similarities and differences.

Occasionally, abnormalities occur that provide a glimpse of the highly orchestrated process of normal eye development. Cataracts, for example, develop when the lens of the eye loses its transparency. This condition usually appears in older people but occasionally appears in newborn babies. When surgical procedures to implant artificial lenses were first developed, doctors were reluctant to perform the procedure on very young children, electing instead to wait until they were older. The results of this well-meaning decision were tragic. The patients remained blind or profoundly visually impaired, even though the original cause of their blindness had been corrected.

What happened to produce this tragic result? The doctors unknowingly assumed that the anatomical structures of the eye and the neural processing of visual information in the brain develop without any input from the environment. What they discovered the hard way is that normal development requires interaction with the external environment in the form of images striking the retina. A cataract prevents this from taking place. Without the environmental input, the physical process of eye and brain development cannot properly occur. The derailed developmental process cannot be restored by introducing the environmental input later in life.

This is a great example of the need to base policy (when to perform surgery on babies with cataracts) on biology (a knowledge of normal eye development). Doctors thought that they were doing the right thing by waiting to remove the cataracts, but their ignorance of the biology of eye development caused them to make a tragic mistake. As they learned more about how the eye develops and its need for environmental input, doctors were able to implement a wiser medical policy about when to perform cataract surgery on very young children.

The development of the eye and visual processing in the brain illustrate a principle that I call rigid flexibility. You already know about this principle if you have used computer software to help you prepare your taxes. The software prompts you for just the right kind of information, which it processes in just the right way to calculate what you owe or (hopefully!) should be refunded. Its ability to calculate anyone’s taxes is impressively flexible, but it is useless for anything else and even fails to correctly prepare your taxes if you feed it the wrong information or change a few lines of code. Its flexibility is therefore rigid and easily broken. The concept of rigid flexibility sounds like a contradiction in terms but makes perfect sense from the right perspective.

The development of the eye and visual processing of the brain is rigidly flexible. Just as the software requires you to enter the right information, the developing eye requires the right environmental input to properly develop. Eons of selection have shaped the developmental process to require inputs that are reliably present in the environment, which is why eye development results in a functioning organ time after time. But change a few lines of the genetic code (such as a deleterious mutation) or create an artificial environment lacking the right inputs, and the process of eye development crashes.

As an example, the neural processing of visual information requires the recognition of contours. This is accomplished mechanistically by some nerve cells firing at the sight of horizontal lines, others firing at the sight of vertical lines, and others firing at the sight of oblique lines. The propensity of each type of nerve cell is hardwired at birth, but unless the cells actually fire in the infant organism, they fail to form the right connections with other nerve cells to process the information. Normally this is not a problem because all natural environments contain an abundance of horizontal, vertical, and oblique lines. What would happen if you raised an infant in a visual environment with only horizontal lines or only vertical lines? Experiments were performed on kittens in the mid-twentieth century to answer this question and resulted in profound visual impairment.

Remarkably, the environments that people build for themselves can hinder eye development, not by limiting the range of contours (as in the kitten experiments) but in other ways. People who grow up in these abnormal human-built environments are unable to focus on distant objects, a condition known as myopia or nearsightedness. Anatomically, myopia is caused by distortions in the physical dimensions of the eyeball, the thickness and curvature of the cornea, and the shape of the lens. Luckily, the condition can be corrected with glasses or contact lenses. If it weren’t for these cultural inventions, myopia would be catastrophically debilitating, as any nearsighted person who has lost their glasses can attest!

This apparatus interferes with eye development without ever touching the eye.

The fact that myopia is caused in large part by an aberrant environment has been known for a long time. One study conducted in 1975 examined Inuits from two settlements in northern Canada.4 Myopia was far more common in younger people than their elders, was more common in women than in men, and correlated with the amount of schooling in both sexes. The transition from hunter-gatherer life to a settled life was causing an epidemic of nearsightedness and schooling evidently had something to do with it.

A more recent study of Jewish teenagers documented that over 80 percent of boys who attended Orthodox schools were nearsighted, compared to around 30 percent of Orthodox girls and non-Orthodox Jews of both sexes.5 The Orthodox boys spent as many as sixteen hours per day in their schools. National comparisons conducted between 1998 and 2004 show that the prevalence of myopia was less than 3 percent in Nepal (with very little schooling) and over 69 percent in Guangzhou province of China (with a lot of schooling).

Clearly, modern human-built environments and/or modern human activities (such as a large amount of time spent reading) disrupts the normal process of eye development. One possibility is the amount of time spent focusing on close objects required by reading or certain occupations such as checking for weaving faults in the textile industry, where the prevalence of late-onset myopia is exceptionally high. However, there is mounting evidence that the main environmental culprit is not the amount of time spent focusing on close objects but the amount of time spent indoors.

In one study that capitalized on a natural experiment, ethnically Chinese children (ages 6–7) living in Singapore were compared to ethnically Chinese children living in Australia.6 There was a whopping ninefold difference in the prevalence of myopia, and the main environmental difference between the two groups was not the amount of time doing schoolwork but the amount of time spent outdoors—an average of fourteen hours a week for the kids in Australia versus an average of three hours a week in Singapore. A 2012 review of all relevant studies to date estimated a 2 percent reduced odds of myopia for each additional hour of time spent outdoors per week.

We are still in the process of improving our theories on the environmental causes of myopia. The theory that myopia is caused by spending large amounts of time focusing on close objects leads to one set of policy recommendations. The theory that myopia is caused by time spent indoors leads to another set of policy recommendations. One theory might be wrong or both might be correct to a degree, and the causes that they postulate might interact in a complex fashion. Only more scientific inquiry can decide the facts of the matter—and only the facts of the matter should inform public policy. Hence, the policy must be based on a detailed understanding of biology. Perhaps this seems obvious to you for something as “biological” as eye development, but my second story will expand the boundary of what is typically considered “biological” into what is typically considered “behavioral” and “social.”

CLEANLINESS IS NOT NEXT TO GODLINESS

In 1847, an obstetrician named Ignaz Semmelweis noticed that pregnant women examined by doctors at the Vienna General Hospital were much more likely to die from puerperal fever than women attended by midwives. More sleuthing revealed that the examining doctors usually came directly from performing autopsies. By the simple expedient of making the doctors wash their hands with chlorinated limewater before examining pregnant women, Semmelweis was able to reduce the mortality rate from 18 percent to 2.2 percent.7

This was a milestone in the acceptance of the germ theory of disease, which had been proposed in various forms since the sixteenth century but wasn’t widely accepted until the end of the nineteenth century.8 It’s easy to conclude from germ theory that the best policy is to get rid of all of them. “Kills 99.9% of all germs” is a frequent boast of disinfectant products. But this reasonable assumption, based on previous scientific advances, turns out to be wrong. Environments that are too clean can lead to diseases of their own.

How can this be? One reason is that not all of the creatures that reside on and inside us are harmful. Many of them, in fact, are helpful. Another reason is more subtle: Regardless of whether the creatures are harmful, helpful, or neutral, they have always been there. Removing them creates an environment that never before existed in the history of our species or the species that gave rise to Homo sapiens. We have just seen what happens to the development of our visual system in abnormal environments. Something similar happens to the development of our immune systems in overly hygienic environments, and the problems of crashing the immune system can be far more difficult to solve than myopia.

The fact that we serve as a habitat for a teeming ecosystem of microbes and other tiny creatures has only recently become a focus among biologists. A term for the ecosystem, microbiome, was coined around the turn of the twenty-first century.9 Mind-boggling numbers are required to describe the size and diversity of our microbiomes. We each begin as a single cell, the union of a sperm and egg, which divides again and again to create and maintain our bodies. As adults, we are made up of approximately 39 trillion cells that interact in a symphony of cooperation to keep us alive. The organisms that use us as a habitat, as if we were a miniature planet, are on the same order of magnitude as our own cells.10 A bacterial cell is much smaller than our cells, so the combined weight of our microbiome is a small fraction of our weight. Our microbiomes include bacteria, viruses, protozoa, and multicellular organisms such as worms and mites. A wild guess for the number of species inhabiting you at this moment is 10,000, but they have never been counted and most of them have never been cultured outside the human body. In addition, the whole concept of a species breaks down for bacteria because of all the gene swapping that takes place. When we bypass the species level and count all the different genes in our microbiomes, they outnumber our own genes by a factor of about 200 to 1.

If you are accustomed to thinking that “cleanliness is next to godliness,” here is a parable to help you get over the idea that all germs are bad and need to be washed away. Imagine that you are a farmer relaxing after a long day. Farming is hard work but it is also immensely satisfying. The horses and cows are in their stables, the pigs in their pen, and the chickens in their coop. There will be eggs, bacon, and fresh milk for breakfast. The garden is growing taller every day. The weeds have been removed, the corn is in neat rows, and the tomatoes are just starting to ripen. Your dog, who has been padding along at your side all day, is curled up at your feet. She’ll start barking if her sensitive ears detect any noises outside, such as a fox approaching the chicken coop. Your house cat is on your lap and the barn cats, too numerous to count, are busy catching mice and having their own litters. Now imagine getting rid of all these species. You would be devastated. If you were a subsistence farmer, you would be dead within weeks. That’s how you should think, at least in part, about your microbiome.

Notice that not all species belong on the farm. There are foxes, mice, weeds, and insect pests that need to be gotten rid of. Work is required to maintain the right species composition on the farm, and some of the species, such as your dog and cats, help with the work. Your microbiome is like a farm that needs to be well managed, and smart policy requires something in between “get rid of everything” and “do nothing.”

Our immune system plays the role of the farmer in my parable, working hard to get rid of the species in our microbiota that don’t belong. Like vision, the immune system operates beneath conscious awareness. We don’t need to think about seeing or about managing our microbiota. In both cases, however, the physical processes that evolved by genetic evolution are mind-bogglingly complex and can only be understood by scientific inquiry. The immune system includes dozens of specialized cell types that work together to hunt down and weed out the pest species on the microbiotic farm. The cell types communicate at a distance using chemical signals, calling each other to infection sites. The immune system even includes its own evolutionary process that produces roughly a hundred million different antibodies and selects those that successfully bind to the surfaces of pathogens, tagging them for removal by other components of the system.

The immune system must also develop in the fetus and during childhood. And just like the eye and visual processing in the brain, the immune system requires inputs from the environment for that to happen. It can’t weed out every organism that it encounters. Somehow the immune system must learn to distinguish the friends from the foes, and the friends need to be present for the learning process to take place. When the friends are removed, then the immune system develops abnormally and can become like a farmer who attacks his own livestock, crops, and even himself.

A macrophage weeding out species that don’t belong on the microbiotic farm

The list of ailments that can result from a compromised immune system is long and includes anxiety disorders, asthma, autism, cardiovascular disease, depression, diabetes, eczema, hay fever, inflammatory bowel diseases, multiple sclerosis, and schizophrenia. Notice that some of these disorders are “physical” (e.g., inflammatory bowel disease) and others “behavioral” (e.g., depression). All disorders have physical causes, however, so the distinction is superficial. Indeed, the immune system is increasingly seen as having a behavioral dimension in addition to a physiological dimension. Behavioral responses such as disgust help prevent us from contracting diseases in the first place. When we get sick, we exhibit a whole syndrome of behaviors: social withdrawal, decreased appetite, lethargy, and a lack of interest in usually pleasurable activities. These are adaptive responses to being sick, just as fleeing is an adaptive response to encountering a predator. They also largely overlap with the symptoms of depression. If the immune system includes both a physiological and a behavioral component, it makes sense that both might be affected when the immune system develops abnormally.11

Most of these disorders are more common in highly developed countries than in countries that live closer to a state of nature—just like the prevalence of myopia—which is one clue that a mismatch between modern environments and ancient developmental processes is the culprit. Other clues in an unfolding scientific detective story include the following:

Children delivered by cesarean section have a higher frequency of allergic disorders than children delivered by normal birth. Evidently, passage through the birth canal inoculates the newborn with the microbiota of the mother.
The use of antibiotics by women during pregnancy increases the frequency of allergic disorders in their children. In this case, even children who pass through the birth canal don’t get the normal microbiota.
Exposure to farm environments during pregnancy or the neonatal period decreases the frequency of allergic disorders in children.
Exposure to natural environments up to the ages of 10–15 reduces the risk of multiple sclerosis later in life.
Use of disinfectants in the home increases the prevalence of allergic disorders. Killing 99.9 percent of all germs is not a good thing!
Restoring a more natural species composition in one’s microbiome, including helminth worms, can result in immediate health benefits in adults.
Chronic inflammatory disorders are more frequent in developed nations. And within these countries, they are more prevalent in urban environments than in rural ones. They include depression, schizophrenia, and autism, which many people do not realize involve an inflammatory component.
People who emigrate from undeveloped nations to developed nations experience increases in inflammatory disorders. Some of the best studies are conducted on children from poor countries adopted by families from developed countries such as Sweden, the United States, and Israel. These children live in middle- and upper-class homes so their maladies cannot be attributed to poor living conditions in their adopted country.
When dust is sampled from the rooms of children, there is a negative correlation between the diversity of microbes in the dust and the risk of asthma. The more diversity there is, the less asthma occurs.
In one study that capitalized on a natural experiment, a genetically homogeneous human population straddles the national boundaries of Finland and Russia. The prevalence of type 1 diabetes is four times greater on the Finnish side than on the Russian side. This difference is accompanied by a striking difference in microbial diversity sampled from homes.
A positive correlation between reduced gut microbial biodiversity and poor control of inflammation is a common finding in animal experiments.
Institutionalized elderly people have a diminished microbiota, which correlates with poor health associated with inflammatory diseases.

These and other clues are summarized in a 2013 article by Graham A. Rook, a microbiologist who calls our microbiomes “old friends.” They have been with us for so long (eons) that we cannot live without them. In a 2015 radio interview he said: “We are not individuals—it is a shocking fact for people to hear this—but we are in fact ecosystems.”12 Most people think of ecosystems as something that is out there, such as a forest or a lake. Many people think that the most pristine and aesthetically pleasing ecosystems are without us, such as wilderness areas. Advocates for the environment appreciate the need for stewardship of the earth’s ecosystems, all the way up to the planetary scale. Against this background, the idea that each of us is a planet that requires environmental stewardship is indeed new for almost everyone. Moreover, your personal ecosystem is intimately connected to the wider ecosystem, as a remarkable study headed by the Finnish evolutionary biologist Ilkka Hanski shows.13

Hanski’s team randomly selected a sample of 118 adolescents living in a 100-by-150-kilometer area of Finland that is environmentally heterogeneous. First, each person was measured for an inflammatory disorder called atopic sensitization, which involves the propensity of the immune system to develop antibodies in response to allergens. Second, the forearm of each person was swabbed to obtain a sample of the microbial community on their skin, which was identified to the level of genus using DNA methods. Third, the amount of vegetation cover in their yard was measured. Fourth, the major land use types within three kilometers of their home was measured. Hanski’s team was studying the linkages between a human malady (atopic sensitization) and the ecosystem inhabited by each person at three spatial scales—their skin, their yard, and the larger area surrounding their home.

The skin microbiota for all 118 people combined included 572 bacterial genera in 43 classes. That’s like a tropical rain forest! Those who were sensitive to allergens had a low diversity of one kind of bacteria (called Gammaproteobacteria), and the statistical association was highly significant. None of the other kinds of bacteria were associated with atopic sensitization. Moving outward in scale, the diversity of the Gammaproteobacteria didn’t have much to do with the vegetation cover of the yard, but it was strongly related to the amount of forest and agricultural land (as opposed to water and the built environment) within a three-kilometer radius. The skin ecosystem was clearly linked to the wider ecosystem.

Thus ends my second story about the need for policy to be informed by biology. It provides another demonstration that the theory decides what we can observe. The advent of germ theory during the nineteenth century enabled us to see the nature of infectious disease, leading to medical and public health practices that vastly improved the quality of our lives. However, a version of germ theory that treats all germs as bad is blind to another set of problems. The amount of suffering caused by the so-called “diseases of civilization” today rivals the amount of suffering caused by infectious diseases in the nineteenth century. A version of germ theory that takes microbiomes and the immune system into account promises to alleviate much of this suffering. As with myopia, some of the solutions might be extraordinarily simple, such as spending more time in natural environments or inoculating babies with a healthy microbiome. Other solutions will undoubtedly be more complex. Either way, the solutions can’t be seen without the right theory, which is firmly rooted in biology.

My second story expanded the boundary of what is typically considered “biological” (such as asthma and diabetes) into what is typically considered “behavioral” (such as depression and anxiety). Once we appreciate that all behavioral traits have a physical mechanistic basis, no less than anatomical and physiological traits, the distinction between “biological” and “behavioral” disappears, as Tinbergen wisely noted so long ago. My third example expands the boundary still further—including the earnest desire of parents to do well by their children.

AN EGG WITH A VIEW

Many developmental processes are rigidly flexible. They evolved to receive just the right environmental inputs, which are processed in just the right way to lead to adaptive outcomes. But they can be subverted by environmental inputs that were not part of the “Environment of Evolutionary Adaptedness.”14

One experiment that was performed on bird eggs provides an elegant (if perverse!) demonstration of rigid flexibility. Sound travels through the shell of a bird egg much better than light. As a result, the auditory system can start to receive environmental input while the developing chick is still in the egg, but the visual system must wait until the chick hatches. That’s how it’s been ever since birds evolved from dinosaurs. What happens if you accelerate the input of visual information by installing a window into a bird’s egg? The installation is a snap to perform but it creates a completely different environment as far as bird development is concerned.

The window installation experiment was performed on bobwhite quail by the developmental biologist Robert Lickliter and colleagues in the 1980s.15 Reading his articles is akin to watching a master scientist practicing his craft. Bobwhite quail are a commercially raised game species, so fertile eggs can be ordered from a supplier and raised in an incubator. Bird eggs have an air space at one end that enables the developing chick to start breathing and vocalizing before it hatches. The eggshell is porous enough to allow air to pass from the outside environment into the air space. The window installation involved removing the eggshell over the airspace on the twenty-first day of incubation, two days before hatching. In a preliminary experiment, Lickliter installed windows into eggs and placed the incubators in a dark room. These chicks developed in the same way as chicks from normal eggs, so the window installation by itself had no effect on their development.

Baby quail can hear their mothers before they can see them.

In the main experiment, a 15-watt lightbulb was placed above the incubators and caused to pulse at 3 cycles per second, because the development of the visual system requires processing visual contrasts and not just a steady stream of light. Care was taken to ensure that the light did not alter temperature or humidity inside the incubator. The only difference between the experimental and control treatments was that the pulsing light reached the eyes of the chicks with windows but not those of the chicks inside normal eggs.

What happened? Bobwhite quail chicks are precocious and are capable of following their mother within a few hours after hatching. To follow their mother, it is critical for them to recognize her call. The auditory system develops while the chick is still in the egg. Installing a window causes the visual system to start developing prematurely, and this interferes with the development of the auditory system. Chicks that hatch from eggs with windows are unable to identify the calls of their mothers, which would be a catastrophic disability in their natural environment.

The fact that sensory systems develop in a certain sequence and at different rates turns out to be quite general. In birds and mammals alike, the order is tactile, vestibular (balance and spatial orientation), chemical (taste and smell), auditory, and visual. The sequence is governed in part by the availability of environmental inputs. If the visual system needs patterned light to develop, then it can’t begin until after birth. In addition, there might be other reasons for the development of sensory systems to proceed in a certain order. Suppose that you are a contractor responsible for building a house with electricity, plumbing, and heating. You might have good reasons to install these systems in a certain sequence, even if they are eventually going to be integrated with each other. Whatever sequence you decide upon, an arbitrary change in the sequence is likely to be disruptive.

Against this background, consider a product called Bellybuds, a sound system for your unborn child. You like listening to Mozart, the Grateful Dead, or Snoop Dogg, so why deprive your unborn child of the same enjoyment? Or consider Baby Einstein, an entire line of educational products for babies that was started by a former teacher and stay-at-home mom and is now a division of Walt Disney. Might these seemingly innocent products be like installing a window into a bird’s egg?

The earnest desire of most parents to do well by their children provides a fine example of theory determining what we can see. If we want our children to go to college and get good jobs, shouldn’t we begin early? Shouldn’t we buy them Baby Einstein products when they are still in their cribs and start teaching them the three Rs in preschool? All of this makes perfect sense when “practice makes perfect” is our guiding theory, just as killing all germs makes sense when we are guided by the wrong version of germ theory. But developmental processes are more complicated than “practice makes perfect.” As soon as we absorb this fact, then our entire perception of reality changes. That which previously made perfect sense and therefore guided our actions becomes dangerously misinformed.

If we want our kids to be well educated, shouldn’t we start early? Maybe not.

Unlike bobwhite quail, humans are an altricial species, which means that a lot of development takes place after birth. Not just sensory development but emotional, social, sexual, and intellectual development. Given that we are such a behaviorally flexible species, in some respects development never ends. For thousands upon thousands of generations, human children were born into their societies and developed into functioning adults. An enormous amount of learned information was transmitted across generations. The social environments of our ancestors were diverse, just as visual environments are diverse (for instance, arctic vs. jungle). As with visual environments, however, ancestral human social environments shared enough in common for developmental processes to receive the appropriate environmental inputs and produce functional outcomes time after time. Now these inputs are in danger of being disrupted by modern social environments, including well-meaning but misguided efforts to do well by our children. It would be hard to imagine a more important priority for scientific research, but because the problem is largely unrecognized, scientific studies are few and far between. Here is some of the evidence that scientists are beginning to piece together:16

Numerous studies have compared academically oriented preschool and kindergarten programs to programs that foster age-appropriate play. Academically oriented programs typically result in narrow academic gains over the short term that wash out within one to three years and in some cases are reversed. In other words, there is evidence that academically oriented programs for small children fail and might even backfire.
There is evidence that academically oriented school programs for small children might harm social and emotional development over the long term. A study in Germany conducted during the 1970s compared the graduates of 50 play-based kindergartens with 50 academic, direct-instruction kindergartens.17 Students who attended the academically oriented kindergartens showed short-term academic gains, but by grade 4 these students were performing significantly worse than students from play-based kindergartens. They were less advanced in reading and mathematics, and they hadn’t adjusted as well socially and emotionally. Based in part on this study, Germany changed its policy and began favoring play-based kindergartens.
One remarkable study led by David Weikart that started in 1967 followed a cohort of 68 children from high-poverty neighborhoods in Ypsilanti, Michigan, to the age of 23.18 The children were assigned to one of three kinds of nursery school: Traditional (largely play-based), High/Scope (play-based with adult guidance), and Direct Instruction (an emphasis on reading, writing, and math using worksheets and tests). In addition, the families of the children were provided with guidance for home instruction similar to what their children were receiving in nursery school. As with other studies, the children receiving direct instruction showed early academic gains that subsequently disappeared. By age 15, there were no differences between the three groups of children in academic achievement but large differences in social and emotional development. Students in the direct instruction group had committed more than twice as many “acts of misconduct” as students in the other two groups. By age 23 the difference had become even more dramatic. Young adults that had received direct instruction as preschoolers were more emotionally impaired, less likely to be married and living with their spouse, and more likely to have committed a crime than young adults from the other two groups—39 percent (compared to 13.5 percent) had felony arrest records and 19 percent (compared to 0 percent) had been cited for assault.
For children less than two years of age, two-dimensional images like books and screens are far less effective learning tools than three-dimensional objects (which include other people).19 Two-dimensional images were a very small part of human experience for most of our evolutionary history. They have become omnipresent in modern life, so we clearly can and must develop the ability to comprehend them. But trying to accelerate this process might well interfere with other important developmental steps.
Despite their popularity and promotion by commercial interests, there is no evidence that educational DVDs and videos for very young children are effective. One study conducted on 12- and 18-month-old children over a one-month period compared four treatment groups: 1) watching a word learning video with the parent encouraged to interact; 2) watching the same video without parent interaction; 3) interacting with the parent without the video; 4) a control condition with no instruction of any kind. Only the third group learned more words than the control group.20
In addition to being ineffective, educational DVDs and videos for very small children can retard the very abilities that they are supposed to accelerate. In one study conducted in 2007, every hour of a word-learning DVD/video watched by 8- to 16-month-olds was associated with 6 to 8 fewer vocabulary words.21
Evidence is accumulating that background media of all sorts (such as television) interfere with early child development, including executive functioning—the ability to plan and regulate behavior. The evidence is so clear that the American Academy of Pediatrics has recommended since 1999 that children younger than two should not be exposed to television and other background media. In one 2014 study led by Jenny S. Radesky at Boston Medical Center, higher levels of media exposure at nine months of age were associated with more irritability, distractibility, failure to delay gratification, and difficulty shifting focus from one task to another—even after controlling for other family and parental characteristics.22
Good old-fashioned play, minimally supervised by adults, is emerging as important for the development of executive functioning. Play is where children learn how to regulate their behavior toward others in a safe and secure atmosphere. Children are highly motivated to play. No one needs to teach them how to do it. Yet, the opportunities for unstructured play are becoming extremely limited in modern life. And it’s not just in schools, but also in overly scripted recreational activities, and in neighborhoods that are considered too unsafe for children to play without adult supervision.23

Thus ends my third story illustrating how policy should be considered a branch of biology. What does it add to the other examples? The first conforms to what most people associate with the word “biology.” If the development of the eye and visual processing in the brain isn’t biological, what would be? Nevertheless, this biological knowledge is necessary to make policy decisions on important matters such as when to remove cataracts in babies and what might be done about the epidemic of myopia in modern life. The skeptical reader, at the very least, must grant my point that policy should be based on biology for eye development.

My second story about the development of the vertebrate immune system also falls squarely into what most people would call biological, but some manifestations of immune system dysfunction are behavioral, such as anxiety, depression, and autism spectrum disorders. My second example therefore reinforces the point made by Tinbergen over a half century ago, that the study of behavior is a branch of biology. No matter how immune system dysfunction manifests, there is an urgent need to understand why it happens and to do something about it; in other words, to develop policies on the basis of biological knowledge.

My third example also starts out biological—the development of sensory abilities in birds—but ends up mostly behavioral. If how we raise our children at home and educate them in school isn’t behavioral, what would be? Yet it is also profoundly biological, as I hope you now agree. The fact is that there is no meaningful distinction to be made between “biological” and “behavioral.” An evolutionary worldview won’t be fully established until the essential insight of Tinbergen becomes common sense for all of us in a wide variety of social policy situations.

I also sequenced my three examples to give a sense of urgency to the need to base policy on biological knowledge. It’s easy to be complacent about the first example because the problem (myopia) has a relatively simple solution (corrective lenses) that has already been worked out. But immune system disorders haven’t been worked out and while some of the solutions might be simple, others will surely be complex. With disruptions of child development, we are faced with the tragic possibility that we are harming our own children, based on our lack of biological knowledge.

Why are some people threatened by the idea of policy as a branch of biology? One threatening connotation is “inability to change.” If something about us is biological, doesn’t that mean that we are born a certain way and can’t do anything about it? Another threatening connotation is the justification of inequality. If some people are born a certain way, might that be used to justify certain types of discrimination?

Once we get over the bogeyman story of social Darwinism, we can define the word “biology” the way that biologists do—the study of living processes—and begin to address policy issues using the biologist’s conceptual toolkit, as admirably summarized by Tinbergen’s four questions. Each of my stories involved an interplay of the four questions with development occupying center stage. Each story shows that development involves an interaction between an organism and its environment and that it is a highly scripted interaction written by an evolutionary process. Departing from the script can cause the process to crash. To the best of our current knowledge, if children spend most of their time indoors on close-focus activities, then they are likely to become myopic. If they live in overly hygienic environments, then they are likely to suffer from inflammatory disorders. If they don’t engage in age-appropriate activities at home and in school, then they might be at risk for impaired executive functioning. That’s threatening. On the other hand, there is something we can do about it by learning enough about such developmental processes to avoid these hazards. Basing policy on biology becomes an essential part of the solution, and that’s alluring.

These stories also provide confirmation that theory decides what we can observe. In each case, harmful policies were practiced because they made sense against the background of certain ideas about the world. It made sense to wait before removing cataracts from babies, to rid the world of germs, and to start teaching our children the three Rs in their cribs. New ideas about the world were required to reveal why these practices might not make sense and to suggest other solutions that were previously invisible.

Better theories are only the beginning. No theory leads directly to the truth. The best that any theory can do is to outline a number of plausible hypotheses, which then need to be empirically tested. Armed with a theory of eye development that is approximately correct, we can say with confidence that myopia is caused by an environmental disruption of normal eye development. But is the disruption largely caused by factors such as spending too much time focusing at close distances, spending too much time indoors at low ambient light levels, and possibly other unknown behaviors? Only more scientific research can tell.

In the following chapters I will tell more stories that show how policy should be considered a branch of biology. We will see that no matter how far afield a given policy area seems to be from “biology” as often imagined by policy experts and the general public, all roads lead to an expanded conception of biology that can be studied by an interplay of Tinbergen’s four questions.