Study links environmental causes to human evolutionary development

If University of Chicago economics professor Robert W. Fogel is right, we may be able to immunize our babies, young children and future generations from diabetes, heart disease, osteoarthritis and other chronic conditions by manipulating their early life.

Speaking at a recent symposium sponsored by W. P. Carey School of Business titled "Pathways to Change: Transforming American Healthcare in the Next Decade," the 1993 Nobel laureate proposed that human beings, on average, are taller, heavier, healthier and live longer than our forebears due to situational evolution — a fascinating blend of technology and physiology called "technophysio" evolution.

He found that the extent and severity of these chronic conditions common to middle and old age stems largely from "environmental insults at early ages, including in utero." The main insult he pinpointed was infectious disease, but other factors are powerful, too. Some recent studies even suggest there may be a two-generation effect. Example: the Dutch famine of World War II caused a spike in perinatal death.

Children born to women who survived famine-period birth or gestation subsequently lost more babies, too. In addition, Fogel said, there is evidence that "children of mothers who were in the first trimester of gestation when the famine struck and who survived infancy have elevated prevalence of coronary heart disease" in their mid-50s.

The intersection of explosive technological growth and physical changes in humans can be plotted against other environmental influences, such as family income. An example is the infant death rate among the very poor compared to the very rich in six large U.S. cities. In 1900 the death-rate gap was huge - a difference of 226 per thousand, with poor babies dying more frequently. By 1950, that gap shrunk to 38 per thousand. There are still very poor and very rich families; but their infant death rates are much closer.

By studying archival records of Union Army soldiers, Fogel and other researchers found that as time goes on, symptoms of chronic disease also are showing up later in life. Back then, Americans were sicker earlier, and lived shorter lives. Example: In 1861, doctors examined thousands of boys and men over age 16, determining if they were fit enough to serve in the war. Those long-ago results are startling.

More than one in six teens was disabled, and more than half of men ages 35 to 39 were disabled. The young men were also sicker than today's youth. Of those between ages 16 and 24 rejected for service, 11 percent got the boot for having cardiovascular disease; 12 for hernias; 8 percent for tooth and gum disease; 7 percent for eye, ear and nose diseases; another 7 percent for tuberculosis and other respiratory diseases, and most of the rest for orthopedic conditions or general debility.

Until recently, experts said that since we are living longer, we're also suffering from chronic disease for a longer period. This conclusion was based on an increase in disability rates in the 1970s and 1980s, a time while the mortality rate continued to drop.

But Fogel said "there has been a significant delay in the onset of chronic diseases during the course of the twentieth century."

Take arthritis, for example. Men who turned 65 years old between 1983 and 1992 showed symptoms of arthritis 11 years later than their counterparts who reached retirement age between 1895 and 1910. For heart disease, Fogel pointed to a nine-year delay in onset; for respiratory diseases, an 11-year delay; and for neoplasms (tumors), nearly an eight-year delay. His conclusion: morbidity declines right along with mortality.

As evidence, Fogel cited a 2000 study of disease prevalence drawn from the National Health and Nutrition Examination Survey. Researcher Dora Costa tracked lower back pain, joint problems, decreased breath/breathing problems, irregular pulse and valvular heart disease in people who were middle aged or older from 1900 to 1910, comparing their results with people middle-aged or older from 1971 to 1980.

She found that people who, in their youth, were not exposed to infectious disease reported better health in later life. Occupational shifts also boosted their health, "accounting for 15 percent of the decline in joint problems, 75 percent of the decline in back pains and 25 percent of the decline in respiratory diseases," Fogel noted.

Then he delivered a timely observation about body size and health. Despite the undeniable health impact of obesity - especially extreme obesity - in modern-day America, the Union Army data (called the "Early Indicators Project"), indicates that chronic disease dropped as Americans got taller and heavier. Fogel mentioned a 1999 study on "the impact of unhealthy environments on the genetic component of the genotype."

Another researcher found other interesting patterns, such as that "short recruits were more likely to develop tuberculosis while in service than taller ones." Comparing military medical records over the span of a hundred years indicates that enlisted men's height increased five centimeters, while BMIs for enlistees ages 31 to 35 years grew from 23 to 26. Crunching the numbers, Fogel said, implied that "changes in frame size explain about 47 percent of the total decline in all-cause mortality at older ages between the beginning and the end of the 20th century.

Researchers began to connect the dots around 1993, he said, recognizing the "environmentally induced change to human physiology." A tipoff was the vast difference in disease prevalence between Union Army veterans at age 65 and World War II veterans at the same age during the late 1980s.

Led by physicians, Fogel said, they developed the "existence of a synergism between technological and physiological improvements that has produced a form of human evolution that is biological but not genetic, rapid, culturally transmitted and not necessarily stable." He added that this process is still going on in both wealthy and developing nations.

Unlike what we think of as traditional evolution, defined as a genetic process of natural selection, technophysio evolution applies only to the last 300 years, and is especially relevant in the last 100 years. Technophysio evolution gives us "an unprecedented degree of control over their environment, a degree of control so great that it sets them apart not only from all other species, but from all previous generations of Homo sapiens," allowing us to "increase our average body size by over 50 percent, to increase average longevity more than 100 percent and improving robustness," Fogel continued.

That control includes things as diverse as the discovery of agriculture about 11,000 years ago, which released some of the labor force from hunting and gathering, to the enormous leap in medical services today. Most important, though, is the decrease in chronic malnutrition through the years, attributed to everything from manufacturing and trade to communications and energy production.

Fogel concluded that we must quit thinking of human physiological capacity as fixed. Instead, every year produces a fresh crop of humans born with specific "health endowments." Their health and happiness from midlife on will share some similarities based on environmental factors impacting their gestation, infancy, childhood, youth and young adulthood.

By manipulating factors related to technology that improve food production, public health practices, diet, medical care, even personal hygiene we may be able to will them a longer life with less chronic disease and disability.




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