She Has Her Mother's Laugh: The Powers, Perversions, and Potential of Heredity (28 page)

Davenport and his wife, Gertrude, combined Jordan's data with other pedigree studies and published all the results in the
American Naturalist.
For the most part, they wrote with clinical detachment about skin color. It would be hard to tell whether they were discussing humans or pea plants. “
Skin color in negro x white crosses is not a typical ‘blend' as conceived by those who oppose the modern direction of research in heredity,” they declared.

In their private correspondences, though, Davenport and Jordan were frank about their ambitions for a greater study of racial heredity. Skin color
was just the start. Jordan went on to publish a study in which he claimed blacks are more prone to tuberculosis than whites. In 1913, he amassed an entire catalog of “unit characters” inherited by Negroes, including physical strength, capacity for routine, and “
melodic endowment.” Intelligence was not on the list, for “the negro cannot undergo mental development beyond a certain definite maximum,” Jordan said.

Davenport shared Jordan's faith in fundamental differences in the mental capacities of blacks and whites. In 1917, Davenport laid out his views in an essay called “
The Effects of Race Intermingling.” Mixed-race children would suffer because the biology of their parents would be mismatched within them. “One often sees in mulattoes an ambition and push combined with intellectual inadequacy which makes the unhappy hybrid dissatisfied with his lot and a nuisance to others,” Davenport wrote.

When Virginia lawmakers began to draft the Racial Integrity Act, Davenport and Jordan pitched in to make it law. Davenport sent advice to the bill's architects, while Jordan worked through Virginia's Anglo-Saxon Club—whose name speaks for itself—to lobby for the bill's passage. The law would stand until 1967, when an interracial couple named Mildred and Richard Loving were convicted of breaking it. The Supreme Court ruled in their favor and struck down the law. By the time the Lovings won their case, many scientists had already decided that race—in the sense of the word as it was used by biologists like Jordan in early twentieth-century America—did not exist.

As Davenport and Jordan were spinning their color tops and drawing their racial pedigrees, other researchers were drawing a different image of humanity. They saw the variations in our species as too complex, and too interwoven with historical events, to reduce to simplistic racial caricatures. Starting in 1897, the sociologist and activist W. E. B. Du Bois led a massive study on the Negro residents of Atlanta. His team measured their weight, height, skull size, infant mortality rates, and a host of other vital signs. Du Bois combined the survey results with a synthesis of worldwide
anthropological research in his 1906 book
The Health and Physique of the Negro American
.

Du Bois did not present the Negro American as a uniform type of human being. Negro Americans were a population, within which individuals varied tremendously in every regard. In turn, the Negro population itself was intimately connected to other human populations. “
The human species so shade and mingle with each other,” Du Bois wrote, “that not only indeed is it impossible to draw a color line between black and other races, but in all physical characteristics the Negro race cannot be set off by itself as absolutely different.”

Like anthropologists before him, Du Bois studied the outward features of humans. But in the early 1900s, other scientists began observing our inner variability. The Polish serologist
Ludwik Hirszfeld proved that blood types were inherited according to Mendel's Law. World War I forced him to put that research on hold, and yet it ultimately provided him with an unprecedented chance to see how blood types varied across human populations.

In 1917, Ludwik and his wife, Hanka, traveled to the Macedonian city of Salonica to work as doctors, treating the thousands of Allied soldiers who were finding refuge in the city. Surrounded by a German cordon, Salonica became “
the most crowded and cosmopolitan spot in the universe,” one observer later said.

The Hirszfelds saw an opportunity to get a global view of blood types for the first time. Up until then, they had studied the blood types only of Germans, with little idea of how they compared to people from other parts of the world. In Salonica, they were living alongside soldiers from as far away as Senegal, Madagascar, and Russia. The Hirszfelds began asking soldiers and refugees if they'd give some blood. Eventually the couple ended up with
samples from 8,400 people, representing sixteen ethnic groups. If the Hirszfelds had tried to gather that much blood in peacetime, their travels might have taken a decade.

The patterns they discovered did not fit any simple division between races. The four known blood types—A, B, AB, and O—turned up in every
country they surveyed. The only distinguishing feature was the proportion of types. In England, 43.4 percent had type A, and 7.2 type B. In India, it was type B that was more common, at 41.2 percent; only 19 percent had type A.

The Hirszfelds calculated a “biochemical race-index” for each country, dividing the frequency of Type A by Type B. The index was highest in northwestern Europe and tapered away to the south and east. The Hirszfelds then grouped these “national types” into three regions: the European type, the Intermediate Type, and the Asio-African type. The Hirszfelds were well aware that the types they were constructing would confuse traditionally minded scientists. How, for example, could Asians and Africans be put in one group? “
Our biochemical index in no way corresponds to race in the usual sense of the word,” the Hirszfelds warned.

The complexity that W. E. B. Du Bois saw in the Negroes of Atlanta, that the Hirszfelds saw in the blood of warring nations, demanded a richer view of heredity—one in which genetic variations were liberally spread across populations and had freedom to flow from one population to another. But in the early 1900s, short of bringing thousands of people together in a besieged city, it was impossible to map the genetic geography of our species. Instead, some of the most important early lessons about race came from other species, such as a little brown fly that lived on the west side of North America.

The fly, known as
Drosophila pseudoobscura
, was studied by a Soviet émigré named
Theodosius Dobzhansky. Dobzhansky spent his childhood catching butterflies and became a published expert on beetles at age eighteen. His childhood insect hunts gave him a deep appreciation for nature's rich complexity. Looking at the markings and colors of his specimens, he could see the enormous variation that a single species could contain. He could spot differences from one insect to another, and he could also observe differences between populations. Biologists sometimes called these recognizable populations subspecies. Sometimes they called them races.

As a young scientist, Dobzhansky learned of Thomas Hunt Morgan's
work on flies. It was a revelation for him. Morgan was tying the visible features of insects that Dobzhansky could see—their wings, their halteres, their spots—to the inner workings of their genes. In 1927, Dobzhansky got a fellowship to spend a year with Morgan in New York. The Soviet Union let Dobzhansky go, assuming he would return home when the fellowship ended. But Dobzhansky cherished his escape from Soviet tyranny and embraced the liberal democracy he found in the United States. He would never set foot in the Soviet Union again.

In 1928, Morgan headed west to the California Institute of Technology, and Dobzhansky went with him to the orange-scented hills of Pasadena. Once Dobzhansky had settled into his new Western home, he drew up a plan to study how genetic variations were spread out over the range of a wild species. He knew he couldn't study Morgan's favorite,
Drosophila melanogaster.
It was a garbage-feeding camp follower. Instead, Dobzhansky picked
Drosophila pseuodoobscura
, a truly wild animal that lived across a range stretching from Guatemala to British Columbia
.
Dobzhansky bought a Model A Ford and started driving into remote mountain ranges to catch flies from isolated populations. Back in Pasadena, he bred the flies and inspected their chromosomes under a microscope.

Comparing one fly to another, Dobzhansky sometimes spotted a section of a chromosome that was flipped. These so-called inversions acted like a crude genetic marker. Dobzhansky would find many of the same inversions in different parts of North America. Just as with blood types, the inversions marked no sharp geographical divisions between populations of flies. At best, they were more common or less so from place to place.

As Dobzhansky surveyed his flies, his thoughts turned to his fellow humans. The rise of the Nazis in the 1930s disgusted him intensely. He found the way they used a biological definition of race to persecute Jews both vicious and antiscientific. While Dobzhansky dearly loved his adopted country, he also recognized the racism that still infested it, including among many of the older American geneticists he met.

Dobzhansky confronted America's race obsession for himself on a visit to Cold Spring in 1936. He met Edward East, a geneticist who had declared
a few years earlier that the Negro race possessed undesirable traits that justified “
not only a line but a wide gulf to be fixed permanently between it and the white race.” On meeting Dobzhansky, East assured him that, as a brilliant scientist, he could not possibly be a genetically inferior Russian. East was confident Dobzhansky must belong to the small population of Nordics who lived in Russia.

Starting in the late 1930s, Dobzhansky began declaring publicly that popular notions of human races and white superiority “
had no basis in biology.” In bestselling books, he explained how populations of any animal were a mix of genetic variants. It might be possible to tell one population from another with statistics, but that was a far cry from claiming that all the animals in one population were alike. In fact, the animals with a single population could be tremendously different, genetically speaking. “
The idea of a pure race is not even a legitimate abstraction,” Dobzhansky wrote. “It is a subterfuge to cloak one's ignorance.”

What was true for flies must be true for humans, Dobzhansky asserted. “
The laws of heredity are the most universally valid ones among biological regularities yet discovered,” he declared. Dobzhansky granted that
humans certainly varied, and that some of that variation was spread out geographically. But if human races were sharply defined, then you'd expect to find sharp boundaries between them. And that was almost never possible. While it might be possible to tell an Australian Aborigine from a Belgian by a trait like skin color, another trait—like the prevalence of type B blood—might unite them.

Dobzhansky didn't want to do away with the concept of races completely. He wanted people to see them for just how modest and blurry they really were. Dobzhansky defined races as nothing more than “populations which differ in the frequencies of some gene or genes.”

After World War II, a number of other geneticists and anthropologists joined Dobzhansky's campaign. Their efforts culminated in an official statement from the United Nations condemning scientific racism as baseless. But
Dobzhansky's new allies pushed the attack further than he had. They demanded scientists give up the term
race
altogether. It was so fraught
with dangerous assumptions that it had to be discarded. The anthropologist Ashley Montagu, for example, switched to using the term
ethnic groups
. But one of Dobzhansky's strongest challenges came from one of his own protégés.

In 1951 a young New Yorker named Richard Lewontin came to Dobzhansky's lab at Columbia to study flies
.
Dobzhansky was the sort of strong-willed professor who steamrolled his graduate students, pushing them to do the experiments he wanted done and to draw the conclusions he had already reached. But Lewontin pushed right back. He was committed to investigating his own scientific questions. What was most important to Lewontin was finding a new way to measure the genetic diversity in
Drosophila pseudoobscura
, Dobzhansky's favorite fly.

In his own work, Dobzhansky had only managed to get a crude measure of the fly's genetic diversity. He inspected the cells of insects for any that had major changes to their chromosomes. Some flies, for example, had long stretches of DNA that were flipped into reverse order.
Lewontin, working with John Lee Hubby at the University of Chicago, developed a new way to look for genetic diversity—one that could detect differences that were invisible under Dobzhansky's microscope.

Lewontin and Hubby would grind up fly larvae and extract proteins from them. They would then put the proteins in a slab of electrified gelatin. The electric field dragged the proteins across the slab, pulling lighter proteins farther than heavier ones. In some cases, the scientists found that all the flies made proteins of the same weight. In other cases, however, some flies had lighter versions and others had heavier ones. And in still other cases, a single fly made both heavy and light versions of a protein.

The different weights of the proteins were the result of variations in the genes that encoded them. Lewontin and Hubby compared the weight of proteins in six populations of
Drosophila pseudoobscura
from Arizona, California, and Colombia. Looking at eighteen kinds of proteins, they found that 30 percent existed in different forms within a single population. In other words, these populations were far from genetically uniform. Even individual flies
were surprisingly rich in variations: on average, 12 percent of the proteins in a single fly existed in two forms.

Lewontin then applied this same approach to humans. In the early 1900s, scientists knew of only a single protein that varied from person to person: the blood-type protein that determines people's ABO blood type. By the 1960s, however, scientists had found a number of other kinds of proteins on the surface of blood cells. And these proteins also varied from person to person. A protein called Rh, for example, is present on some people's cells and missing from others'. Doctors have to make sure the Rh factor is the same in a donor and a patient before transfusing blood. Lewontin reviewed studies on these proteins carried out in England. People there had a surprisingly high level of genetic diversity: A third of the proteins varied from person to person.