Advocates of eugenic measures to enhance the quality of the human “stock” sometimes tried to win support for the cause by ridiculing or condemning a contrary view termed “environmentalism.” In this context, environmentalism is the belief that the most important reason people differ from each other in their thinking and behaviour is that their environments and upbringing differ. In the nature-nurture debate, it favours nurture and relegates nature to a minor position. Environmentalism views environment as the decisive factor that needs to be understood and enhanced in order to build a better world. It is the opposite of genetic determinism that attributes most differences among people to genetic differences inherited from the parents, a view that favours the “nature” side of the equation. Environmentalist beliefs pose a challenge to eugenics because the success of a eugenic policy requires that people low in ability or having intellectual defects suffer because of defects in heredity, not unfavourable environments. If bad environments are the principal cause of poor mental performance, social policies to improve the environments of children would be more effective. Eugenicists, however, generally opposed government measures to enhance the quality of life for the poor (Black, 2003; Chase, 1975).

Today, one rarely sees the term environmentalism used in this sense. Instead, the term is used to describe those who advocate for the health of the global environment and oppose changes wrought by human civilization that degrade the natural environment. In modern psychology and biology, it is difficult to identify anyone who self-identifies as an environmentalist and denies the importance of genetic factors in human development. Most of those who specialize in the study of environmental factors that are important for mental development nevertheless acknowledge the importance of genes for nervous system development and health (e.g., Gottlieb et al., 2006; Hood et al., 2010).

It is generally understood among scientists that two kinds of factors are involved in human development: heredity and environment. Heredity consists of all parts of the fertilized egg that are acquired from the parents at conception. Environment consists of things outside the individual that impinge on him or her. The 22 pairs of chromosomes and the X and Y chromosomes (girls are XX, boys are XY) contain most of the genes. The mitochondria in each cell also contain some genes, and they are inherited entirely from the mother. Genes tend to remain the same over a person’s lifetime, except when there is a rare mutation that suddenly alters a gene. Thousands of genes are known to be important for nervous system development and function (Maheu and Macdonald, 2011; Wahlsten, 2013). In most people most of these genes are normal and cannot be blamed for someone’s failures or credited for great successes.

Environment is very complex and can change rapidly. Global influences such as temperature and gravity are usually the same for all people living in the same locale. Substances from the environment that are ingested and digested as part of the diet or absorbed through the skin are assimilated to become part of the individual. The fertilized egg is microscopic, and the organism grows larger by converting things from the environment into its own body. There are also experiences via the sense organs (vision, hearing, smell, taste, touch) that provide vast amounts of information to the nervous system about the external world. Experiences can influence how the individual develops and alter the structure of the nervous system itself. The kinds of things we experience are governed by cultural factors and the social environment. Diets and cultural experiences differ greatly between members of most societies, and these vast differences can play a major role in psychological differences among people.

A belief that environment is critically important for child development does not conflict with what we know about genes (Wahlsten, 2002, 2003, 2013). Clearly, a mutation that causes a major defect in a gene can cause grossly abnormal development, but those kinds of defective genes are so harmful that they are usually not passed to the next generation. They are eliminated from the population by natural selection and therefore tend to be quite rare.

Eugenics as a political program was not aimed solely to reduce the frequency of rare defects of heredity. Instead, eugenics took aim at much more common problems such as low intelligence where no specific genetic cause could be identified. The possibility that poor environments were to blame for low intelligence posed a major challenge to the eugenics creed. Eugenicists in Canada answered that challenge simply by denying the role of a child’s environment and then ignoring it when making a decision about who should be sterilized. As documented in Leilani Muir’s life story (Muir, 2014), the Alberta Eugenics Board failed to consider adverse home environments when making their decisions. They believed as a matter of faith that genes were to blame and sterilization would halt the spread of bad genes.

Several decades of scientific research have shown that the distinction between what is hereditary and what is environmental is often not so clear. The early environment in mammals is provided mainly by the mother, and the maternal environment can function as a part of heredity. Its contribution can be examined by specialized analytical research methods (Carlier et al., 2000). It is also apparent that many influences in the early environment can alter the ways in which genetic information is expressed, and those alterations can be transmitted across generations. Such “epigenetic” phenomena are the focus of many recent studies, and evidence for their importance is accumulating (Burggren, 2014; Dias and Ressler, 2013; Stankiewicz et al., 2013). These findings show why one-sided views such as environmentalism and genetic determinism are no longer tenable.

-Douglas Wahlsten

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