There is an old adage that goes, "A little knowledge is a dangerous thing." The eugenics movement of the early part of the 20th century illustrates this lesson clearly.
The first twenty or so years of the century were the birth period of the science of genetics. Though the basic concepts of genetics were described in 1865, that description made no impact on the developing science of biology. It wasn't until the rediscovery of Mendel's concepts in 1900 that genetics really got its start. So those early years represented a period of tremendous exploration of the twists and turns of genetics.
Naturally, the subject of most interest to almost everyone was the genetic control of features of human beings. Many of the quirks and traits which geneticists studied were very simple and relatively straightforward, like eye color and tongue rolling.
Unfortunately, a number of geneticists decided that other, more subtle human characteristics must be controlled by the same simple mechanisms they found in traits like eye color. They began to discuss with each other the genetics of personality traits, talents and, especially, intelligence.
This was also a period of rather simplistic understanding of evolutionary processes. Those interested in the genetic nature of human characteristics came to feel that, since they now understood both genetics and evolution, it should be possible to take control of our own evolutionary development. Thus was born the "science" of eugenics ("eu"=good; "genesis"=origins). Eugenics is the attempt to "improve" human beings by controlling the nature of the genes that get passed to the next generation, either by encouraging those with desirable traits to have a lot of offspring ("positive" eugenics), or by discouraging those with undesirable traits from having any offspring ("negative" eugenics).
The origin of the basic eugenics concept is generally attributed to Charles Galton, who was, interestingly, Charles Darwin's cousin, though they disagreed about almost everything. The three countries who got most caught up in the excitement of these revolutionary new ideas were England (where a lot was said and written, but no real action was taken), the United States and Germany. The US and Germany both went beyond talk and actually took action to implement eugenic principles.
Germany's eugenics programs under Nazism are notorious. Not only did these programs attempt to eliminate the passage of "bad" genes eventually by eliminating the carriers of those genes some believe they also included breeding stations where those deemed to carry the best of characteristics were instructed to make babies.
But those of us in the United States should think carefully before we point fingers. Our own eugenics actions don't bear up under scrutiny. In the 1920s several states passed Eugenics Laws. These laws were aimed at the elimination of what was called "feeble mindedness." In other words, their purpose was to increase the average intelligence by getting rid of "stupid" genes.
Under the eugenics laws, the state could sterilize any person who was (1) institutionalized in a public institution, like a jail, asylum, or orphanage, and (2) deemed to be feeble minded. No permission (or even knowledge) was required of the person who was to be sterilized. When you consider that this was also the heyday of the US brand of Social Darwinism, you should see that "feeble minded" could encompass a wide range of characteristics. Thousands of Americans were sterilized under the auspices of these laws.
The eugenics laws underwent a constitutional challenge in their early years. They passed. Since the laws have already passed the constitutional filter, states have been reluctant to repeal the laws, and for the most part the laws are still in existence.
So what is so bad about all of this? Aside from the ethics of this kind of assault on human rights, the entire eugenics concept is based upon faulty science.
The problem is that the human features which were of such interest to the eugenicists are not simple, straightforward traits. We have spent at least two centuries trying to figure out how to define and measure intelligence. If we can't define it, how do we judge the ways in which genes affect it? While it is clear that genes have a significant effect on intellectual ability, they are also clearly only part of the story. Then, too, the genetic effects are not simple there are obviously many genes involved, most of which have a variety of other effects upon the organism besides whatever influence they may exert over intelligence.
The basic premise of eugenics depends on the assumption that the traits being controlled are completely understood and simple. For many traits (and particularly for those traits of most interest) this basic premise is false, and for those traits eugenics will not be able to produce significant results.
This subject merits a final, rather contrary note. Eugenics measures can work, if the trait targeted meets the criteria of being simple and well understood. For instance, there is a nasty genetic disorder called Tay Sachs Disease. This disorder is found primarily among one facet of the Jewish population. The cause and biochemistry of Tay Sachs Disease are clearly understood. It is controlled by a single gene, and a person has to inherit two copies of the damaged Tay Sachs version of the gene to have the disease. It is also possible to detect when a person carries only one copy of the damaged version of the gene. They don't have the disease, but a relatively simple medical test can detect the presence of the hidden Tay Sachs gene.
A number of years ago, some ambitious genetic screening and counseling programs were undertaken to try to reduce the frequency of this disease. Those who were at risk of being carriers were tested and advised about the nature of the disorder. Couples in which both carried the gene were counseled about the possibility of producing sick babies; often, they chose either to have no children, or to have prenatal diagnosis performed on those they did conceive, with the intent of aborting the affected fetuses.
This attempt has been very successful at greatly reducing the number of Tay Sachs babies born every year. So eugenics can work, as long as those two vital conditions are met the trait must be genetically simple and well understood.