Gene editing and eugenics

A study published last week in the journal Cell has led to speculation that a powerful new gene editing technique is about to be developed.

Gene editing has received widespread media coverage over the past few months. Most of the excitement has centred on a specific gene editing technique, the CRISPR-cas9 system. Research conducted with CRISPR-cas9 on human embryos has been highly controversial, at least partly because some people fear it will lead to gene editing being used to alter the human germline for clinical applications, and will have unpredictable effects on future generations.

Some criticisms that have been levelled at gene editing in the wake of this research overlook the fact that it is unlikely that the cas9 system will be the specific gene editing tool used for widespread clinical applications in humans. Since the first gene editing technique was described 5 years ago, there have been 4 different gene editing systems developed, with cas9 being the latest and most accurate. But by the time cas9 would be considered for clinical applications in humans, it is likely that better gene editing tools will have been developed.The recent study published in Cell provides evidence that the enzyme Cpf1 can be used to edit genes in a more precise way than cas9.

Other objections levelled at the cas9 system apply to all gene editing techniques, no matter how advanced.  For instance, many object to gene editing on the grounds that it is eugenic, or will lead to eugenics.[5]  In justifying their call for a ban on gene editing, a recent UNESCO panel said such technologies could “renew eugenics”.

This same criticism has been made of other reproductive technologies which affect the human gene pool. Not long after its development, Preimplantation genetic diagnosis (PGD) was objected to on the basis that it is a eugenic activity.[1] Gamete selection technologies, such as the one patented by genomics company 23andMe, have also been labelled eugenic.

However it is not obvious what it means for a practice to be eugenic, or why eugenics is a bad thing. Despite the frequency with which eugenics is referred to in bioethics, there is surprisingly little consensus on what eugenics actually is.  Take the following descriptions of eugenics:


a practice that aims to improve human lives by employing an understanding of heredity in the exertion of control over who gets born or who reproduces.[2]


the attempt to improve the human gene pool.[3]


manipulating heredity or breeding to produce better people and on eliminating those considered biologically inferior.[4]


 the positive selection of “good” versions of the human genome and the weeding out of “bad” versions, not just for the health of an individual, but for the future of the species.[5]


using science and/or breeding techniques to produce individuals with preferred or “better” characteristics.[6]


From the above quotes we can see that the goals of eugenics have been interpreted in at least two distinct ways. Some see eugenics as primarily about making better people, whereas others see it as primarily about making better populations. We can therefore make a distinction between genome eugenics – which understands eugenics as fundamentally about improving the heredity of individuals, and gene pool eugenics – which understands eugenics as improving the heredity of populations – or the species as a whole.

In order to better understand eugenics, and what relevance it has to current debates about reproductive technologies, we need to understand why eugenics has been interpreted in these two different ways. Eugenics, when first described by Francis Galton in 1904, saw no distinction between the aims of improving genomes and improving gene pools. Galton thought that there was an ideal set of hereditary material for humans to possess – which would enable an individual to become “the best specimen of his class”.[7] This ideal hereditary material benefits individuals as it allows them to develop desirable traits, such as health. Underlying early eugenics, then, is the idea there is ideal genetic material for humans to possess – genes which would be beneficial for all humans.

Galton also thought that the ideal human heredity would benefit society as a whole. He believed that many of society’s problems, like crime and poverty, were caused by poor heredity. The greater the proportion of individuals who possessed good genes, the better off society would be. Hence, improving the genome of individuals would have the added benefit of improving the human gene pool.  As the ideal set of hereditary material for humans to possess was limited, society would benefit from an homogeneous gene pool, in which the ideal genetic material is very frequent. Another central idea of early eugenics, then, is that the best possible gene pool would contain little diversity.

These central ideas of early eugenics – that there are objectively good genes and that homogeneity is good for the gene pool, are incompatible with our modern understanding of genetics. Genes only have effects within particular environmental contexts. Genes which are good for one individual’s health or well-being may be detrimental to another’s, due to subtle differences in their circumstances. The idea that there is a perfect human genome is a myth.  For similar reasons, we know that homogeneity in the gene pool is often disastrous for populations. Genes adaptive in one generation may be maladaptive in the next, due to environmental changes. Diversity in the gene pool is vital for the ability of populations to flourish and persist through time.

When the term eugenics is used in the current debate about gene editing, we should clarify exactly which aspects of eugenics are being referred to. Specifically we should distinguish the broad goals of eugenics (improving individual genomes and improving gene pools), from the specific ideas early eugenicists had about how these goals would be achieved.  We have good reasons to completely reject the idea that there are objectively good human genes and that society would benefit from an homogeneous gene pool. However we shouldn’t conclude from this that there are no good ways we could use gene editing technologies to improve genomes or gene pools for the benefit of humanity.

[1] Freeman JS. Arguing along the slippery slope of human embryo research. J Med Philos1996;211, 79,.

[2] Selgelid M. Moderate Eugenics And Human Enhancement’. Medicine, Health Care and Philosophy 17.1 (2013): 3-12.

[3] Wilkinson, S., & Garrard, E. (2013). Eugenics and the ethics of selective reproduction. Keele: Keele University.

[4] Kevles DJ. Eugenics and human rights. BMJ : British Medical Journal. 1999;319(7207):435-438.

[5] Pollack R. Eugenics lurk in the shadow of CRISPR. Science. 2015;348(6237):871-871.


[7] Galton F. Eugenics: Its Definition, Scope, And Aims. Am J Sociol  1904:1-25


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