CLEVELAND – For thousands of years, humans have used genetic engineering to control the evolution of plants and animals. So it is inevitable that we will use it to shape our own evolution. Our efforts so far have been modest: online dating services are beginning to match subscribers on the basis of their genetic compatibility; parents increasingly screen embryos and fetuses, allowing only those with the healthiest genes to be born; geneticists are only slowly improving their ability to manipulate DNA directly; and no one is trying to make germline changes in humans that will be passed on to succeeding generations.
Full-scale human evolutionary engineering is still far off, but, at some point in the future, it may well become routine. The challenge for humanity is twofold: to survive long enough to reach that point, and to cause the least amount of harm while getting there.
Those most immediately at risk are children, who are in danger of having their genetic material manipulated in damaging ways. The harm can be physical (stillbirths, deformities, and genetic disorders); but, even genetic engineering that is technically successful can cause psychosocial harm to children, who may be shunned by peers for being odd-looking or merely “different.”
On a societal level, genetic engineering that only the wealthy can afford would threaten social cohesion by ruling out equality of opportunity. Genetic haves and have-nots could form separate castes, with reproductive isolation possibly producing physical changes that would make inter-caste procreation impossible. Ultimately, this could lead to the emergence of distinct human species.
Given that no human species other than our own survives (Homo floresiensis disappeared about 18,000 years ago), the prospects for harmonious coexistence among future human species are not reassuring. In the worst case, the human genetic lineage itself could be wiped out by inter-species conflict.
Even without speciation, the same outcome could occur through a loss of genetic diversity: If everyone selected the same traits for their offspring, their descendants would be incapable of surviving a sudden, unexpected environmental challenge.
Geneticists often express skepticism about such predictions. For example, a reviewer of my recent book, writing in Science, pointed out how little impact “a few genetically engineered individuals” will have on the human gene pool. But, while it is true that a genetic-engineering catastrophe will not overtake the entire human species anytime soon, existing genetic-engineering technologies already can harm individual children: witness the increase in premature births and low birth weights associated with in vitro fertilization. And reproductive decisions that reflect a cultural preference for boys are beginning to produce social problems in countries like China and India.
Simply put, in the absence of unknown and unforeseeable technical impediments, human evolutionary engineering is likely to become sufficiently widespread in the future to pose species-wide threats. So, while it may not be necessary to employ measures now to prevent harm in the future, it makes sense to identify which measures might be needed, together with the changes in social norms and behaviors that might be required to implement them.
Many of the risks from evolutionary engineering are triggered by bad parental decision-making. Eager to give their children social advantages, parents may make reproductive decisions based on faulty or incomplete genetic information, or seek genetic alteration of their offspring before adequate safety testing has been carried out.
Determining when it is permissible to interfere with parental choices is challenging, given the deference that parents typically receive. Most countries have laws aimed at protecting children from abuse and neglect. But legislation to safeguard children’s welfare does not adequately address harms produced or set in motion before birth, or establish which types of evolutionary engineering are acceptable.
Most of the reproductive decisions parents make cannot be carried out without the aid of professionals such as physicians, so it might be necessary to regulate professional behavior as well. While some of the infrastructure, such as licensure laws for physicians, is already in place, additional steps may be needed, such as heightened regulation of infertility clinics, where many genetic-engineering interventions will take place. Furthermore, rules must be established for assessing the safety and effectiveness of new technologies with respect both to immediate recipients and their descendants.
Some forms of evolutionary engineering that do not directly harm individuals, and therefore would not be subject to such regulations, such as decisions by all parents to make the same genetic changes in their offspring, could threaten the survival of the human lineage. Public-health systems could respond to this concern. Yet, in view of past efforts by officials to employ genetics to improve public health – most notably, the early-twentieth-century eugenics movement, with its appalling forced sterilization campaigns – it is important to ensure that such power is wielded judiciously and on the basis of sound science.
Finally, if too few members of society enjoy too great a genetic advantage, social cohesion and democratic institutions could be threatened even in the absence of any direct physical harm. If the genetic engineering that we allow is to benefit our descendants, it must be as widely available as possible.