The advancement of science is often considered the antibiotic that cures superstition. Yet historically, this is not always the case. The eugenic movement of the early 1900s is such an example, which went horribly wrong despite its noble goals of using science to improve humanity. Francis Galton, who first coined the term eugenics, believed that negative traits can be weeded out from the human population through selective breeding. Although this idea seems plausible and scientific, the actual practice of eugenics had very little basis in genetics.
Early eugenicists used Mendel’s laws as the basis for their reasoning. By breeding pea plants, Mendel has found a pattern of inheritance for certain traits, such as plant height and flower color. The first generation of two true breeding plants all showed the flower color of one of the parents, but the second generation showed both flower colors. This led Mendel to hypothesize that a dominant and a recessive allele exist for each trait. He thus deduced the law of segregation, which concludes that genetic factors segregate during gamete formation and end up in different gametes, and the recombination of gametes from two parents determine the new phenotype of the offspring. Mendel also devised the Punnett square, which was a simple way to predict the genotypes of the offspring given two parents with known genotypes.
A major problem with the study of eugenics is the belief that human traits are controlled by a single gene like the coat color and plant height in Mendel’s experiments. In reality, the inheritance of most human traits is multifactorial and largely unpredictable with observation on the organismal level alone. Mendel’s laws only addressed the phenomenon of complete dominance and the existence of dominant and recessive alleles. However, scientists have now discovered a myriad of exceptions to Mendel’s laws, which complicates the nature of genetic inheritance. One example is polygenic inheritance, which states that some phenotypes, such as height and skin color, are influenced by multiple genes. Most human traits are polygenic and are quantitative, meaning that the distribution of these traits in the population often follow a continuum. So who’s to say where the line between normality and deviance should fall in this continuum? Other traits like personality, the ability to learn, and the tendency to commit crimes are all based on complex interactions between genes and the environment and cannot be predicted based on inheritance alone. Thus, based on the complex nature of human inheritance and the intricate interplay between nature and nurture on an individual, eugenics is destined to fail from the beginning.
However, eugenicists had not yet known about the multifactorial nature of human inheritance. Equipped with only knowledge about monohybrid inheritance, they reasoned that by tracking family pedigrees, they will be able to identify individuals with “negative” genes and prevent them from breeding, thus eliminating these traits from the population. The problem with this approach is that most of the “negative” traits eugenicists studied were defined in vague terms such as “criminality,” alcoholism, and “feeblemindedness,” which was a broad word that could be applied to varying degrees of mental disabilities. These traits were closely linked with social and environmental factors such as education level and economic status, which were not accounted for in eugenics research.
In addition, research on eugenics were highly unreliable. When collecting pedigrees, direct interviews with family members are often unavailable. In these cases, researchers deemed these individuals “fit” or “unfit” solely by relying on tell-tale evidence from family and friends, which made the research seem more like a witch hunt. Also, the definitions for the conditions they searched for (such as criminality and feeblemindedness) are so vague that anyone could have been identified as “unfit.”
The flawed science of eugenics had harmful implications in society, especially during the economic and political unrest of the early 1900s. Many city governments blamed issues of crime and poverty on immigrants instead of trying to fix the problems through urban development. Eugenics also led 30 states to adopt sterilization laws, which altogether resulted in the forced sterilization of approximately 60,000 people considered “socially inadequate” (those who depend on public assistance). The movement also contributed to the ethnic bias that led to the Immigration Act of 1924, which remained in place until the 1960s.
These repercussions of this 20th century pseudoscience should serve as a warning. In an age of rapid scientific advancement, it is vital for us to remain open yet rational towards new scientific theories. Only then, can we enjoy the benefits of science without being misled into the realm of prejudice.