More Than Genes: What Science Can Tell Us About Toxic Chemicals, Development, and the Risk to Our Children
We are all shaped by our genetic inheritance and by the environment we live in. Indeed, the argument about which of these two forces, nature or nurture, predominates has been raging for decades. But what about our very first environment--the prenatal world where we exist for nine months between conception and birth and where we are more vulnerable than at any other point in our lives?
In More Than Genes, Dan Agin marshals new scientific evidence to argue that the fetal environment can be just as crucial as genetic hard-wiring or even later environment in determining our intelligence and behavior. Stress during pregnancy, for example, puts women at far greater risk of bearing children prone to anxiety disorders. Nutritional deprivation during early fetal development may elevate the risk of late onset schizophrenia. And exposure to a whole host of environmental toxins--methylmercury, polychlorinated biphenyls (PCBs), dioxins, pesticides, ionizing radiation, and most especially lead--as well as maternal use of alcohol, tobacco, marijuana, or cocaine can have impacts ranging from mild cognitive impairment to ADHD, autism, schizophrenia, and other mental disorders. Agin argues as well that differences in IQ among racial, ethnic, and socioeconomic groups are far more attributable to higher levels of stress and chemical toxicity in inner cities--which seep into the prenatal environment and compromise the health of the fetus--than to genetic inheritance. The good news is that the prenatal environment is malleable, and Agin suggests that if we can abandon the naive idea of "immaculate gestation," we can begin to protect fetal development properly.
Cogently argued, thoroughly researched, and accessibly written, More Than Genes challenges many long-held assumptions and represents a huge step forward in our understanding of the origins of human intelligence and behavior.
depend substantially on differences in prenatal environment. In America, the populations of pregnant women (and their fetuses) who are most exposed to environmental lead pollution are those living in the inner cities. They tend to live in old buildings containing leaded paint or dust from the scrapings of old leaded paint, and the soil around their buildings is contaminated with lead. These old buildings also tend to have lead pipes in their plumbing systems. We know from measurements that these
incineration. They readily pass into and accumulate in living systems. Animal experiments have demonstrated that these chemicals can produce mutations and fetal malformations. They have also been implicated as human carcinogens. PCBs are another group of chemicals with many industrial applications (for example, adhesives, wood ﬂoor ﬁnishes, and paints), and like dioxins are extremely stable and persistent organic pollutants. In the United States, they were used commercially for 50 years before
program risks in the fetus for adverse health outcomes, such as cardiovascular disease; obesity; and metabolic syndrome in adult life. An ampliﬁcation of this idea is that fetal programming is an evolutionary adaptation that activates the hypothalamic–pituitary axis to produces an early ﬁtness advantage (fetal survival) at the cost of later adult disease. This raises an important question: Is it possible that evolved fetal programming to achieve fetal survival can also occur at the cost of later
a diagnosis of epilepsy by age 80.14 In general, any prenatal impact that causes a developmental neuropsychological disability also has the potential to be responsible for epilepsy. Cortical malformations of various types are often coupled with epilepsy in the clinic: for example, approximately 75 percent of children with magnetic resonance imaging (MRI)-recognized cortical malformations have occasional or frequent seizures.15 But cortical malformations can be present without seizures, and there
responsibility belongs to society writ large—to local, state, and federal government, to industry, to an unknowing or misled public, and to media ballyhoo that ignores science and instead puffs heredity as the primary determinant of human behavior and intelligence. America currently has a heavy bundle of social, economic, and political problems related to the prenatal environment, but THE RICHNESS OF OUR IGNORANCE s 23 the burden of responsibility for allowing these problems to continue