By the year 2040, embryo selection could replace sex as the way most of us make babies

One intelligent athlete, coming right up.
One intelligent athlete, coming right up.
Image: Reuters/Michael Dalder
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Human reproduction is about to undergo a radical shift. Embryo selection, in connection with in-vitro fertilization (IVF), will help our species eliminate many genetic diseases, extend healthy lifespans, and enhance people’s overall well-being. Within 20 years, I predict that it will supplant sex as the way large numbers of us conceive of our children.

But while the embryo selection revolution will do a lot of good, it will also raise thorny ethical questions about diversity, equality and what it means to be human–questions we are woefully unprepared to address.

IVF for humans has been around since 1978, the year Louise Brown, the first so-called “test-tube baby,” was born in the UK. Since then, nearly six million infants around the world have been conceived via IVF, with the procedure growing in popularity each year. Starting in the 1990s, doctors began using preimplantation genetic screening (PGS) to extract cells from early-stage embryos and screen them for simple genetic diseases.

At present, over a thousand such diseases, including cystic fibrosis, Huntington’s disease, Tay-Sachs, sickle-cell anemia, and Duchenne muscular dystrophy, can be screened during PGS and the list is growing constantly. With this information, parents using IVF and PGS can select embryos not carrying those diseases if they choose to do so. Some jurisdictions, including the US, Mexico, Italy, and Thailand, also allow parents to select the gender of their future children.

These are still the early days of PGS. The process of linking single gene mutations to specific diseases has been slow and painstaking, but also relatively straightforward. As increasingly more people have their full genomes sequenced, an essential foundation for the future of personalized medicine, scientists will be able to uncover and screen for genetic and epigenetic patterns underpinning far more genetically complex diseases like epilepsy and type 1 diabetes.

As the PGS procedure improves and the number of diseases it prevents increases, I foresee that growing numbers of parents will decide to use assisted reproduction technologies when conceiving children. Over time, many genetic diseases will come to be seen as preventable parental lifestyle choices rather than bad luck. People will be free to opt out of laboratory-managed conception for religious, ideological, or economic reasons—or in fits of passion. But having children through IVF and embryo selection will become the norm for parents of all ages and genetic predispositions. We’ll still have sex for most of the wonderful reasons we do now, just not to have babies.

In the few countries like Australia, France, Israel, and Sweden, where assisted reproduction is covered by national health plans, the popular shift toward managed conception will not pose challenging questions of socio-economic equity. In other countries where the cost of IVF and PGS remains high—the procedures currently cost up to $20,000 in the US—the equity challenge will be greater. And in the poorest countries, IVF and PGS may not be available at all.

But as IVF and PGS become more widely accepted, the cost will go down and access percentages will go up. In many countries, governments and insurance companies will have strong incentives to cover the expense of IVF and embryo screening. This cost will be far less than that of providing lifetime care for all the children born with preventable genetic diseases in the absence of screening. (Another option would be pre-natal screening of embryos during pregnancy, a far more morally fraught process with significantly fewer benefits.)

Even as the procedures become more prevalent, IVF and PGS will not be without risk. Egg extraction can be extremely painful and sometimes even dangerous for women. Early-stage embryos can be damaged during the biopsy process, and up to a fifth of the embryos may not survive cryogenic freezing prior to implantation. The process can also be expensive, time-consuming, and stressful for parents. And a preliminary study released in the Journal of the American Medical Association (JAMA) earlier this year suggested that children born from IVF may be slightly more likely to carry certain birth defects than their non-IVF peers.

The ultimate question for prospective parents, however, will not be whether or not IVF and PGS carry risks, but whether these risks are greater or lesser than the risks of conceiving children the old-fashioned way. The JAMA study indicated a .001% increase in the likelihood of defects for children conceived via assisted reproduction technologies. This number is too high, but a far higher percentage of children—the UK’s Royal College of Physicians puts the number at two to three percent—are born with congenital or genetically-determined abnormalities. Not all of these abnormalities can currently be screened in PGS, but a significant and growing number of them will be covered as knowledge of the genomic indicators of disease expands. The odds will tilt further in favor of assisted reproduction because women planning to conceive via IVF later in life will be able to extract and freeze their eggs in their twenties, when the risk of genetic abnormalities is significantly lower than in their mid-30s and beyond.

The ability to prevent genetic disease will catalyze the adoption of embryo screening across the population. But our use of the technology will not end there. When cells taken from early-stage embryos are fully sequenced during PGS, they will provide information about all genetically influenced traits, not just those related to disease.

As millions and then billions of people have their genomes sequenced as part of standard health care and these people’s genomes are compared to their life experience, scientists will deploy big data analytics to uncover how certain genetic and epigenetic patterns increase the probabilities of various outcomes.

There is no absolute answer to the nature-nurture debate, and it is impossible to determine precisely what percentage of our traits are based on our genes. Scientists have estimated based on twin studies, however, that the range is somewhere between 50-80%. Some traits, like having wet ear wax or being able to roll your tongue, are more genetically simple, perhaps only influenced by one or more genes. Others, like height and intelligence, are more complex and influenced by thousands.

The science is complex, but Stephen Hsu, a professor at Michigan State University with an extensive background in genomics, estimates we’ll be able to use genome-wide association studies to roughly predict height from cells taken from early stage embryos within a couple of years and intelligence within a decade.

In jurisdictions where PGS screening for trait selection is allowed, parents will be informed of the probabilities of likely outcomes from among their pre-implanted embryos when deciding which of them to implant. Some embryos will be identified at having a greater than normal shot at being brilliant at math, or exceptionally fast runners, or super-empathic children. The more we know of genomics, the more accurate these predictions will become.

As complicated as this all sounds, scientists won’t need to fully understand the genome to move forward safely.

The more we learn about the incredibly complex ecosystem of the human body—the interaction between the genome, epigenome, microbiome, virome, connectome, and old-fashioned life experience—the more we realize how little we understand. But with embryo selection, it hardly matters that our knowledge of the genome is so basic. All the pre-implanted embryos will be the natural and unadulterated potential offspring of their parents. Choosing among them will be a choice among natural options. We don’t need to be smart enough to precisely edit the right genes or make completely accurate predictions about the outcomes, just confident enough to offer a best guess on which embryo to implant based on our limited knowledge. The potential benefit of making a good decision will be high, the cost of making a bad one no worse than the random outcomes of traditional sex.

This brave new world of assisted reproduction will frighten many people. Many individuals, groups, and countries may choose to opt out for very legitimate reasons. But competition within and between countries will drive the adoption of embryo selection inexorably forward. Once it is considered safe, parents will not want their children to be left behind as IQ levels across the population increase, or the average height becomes taller, due to embryo selection. Countries will fear losing competitiveness if they opt out while other states opt in.

All of this will raise fundamental questions that, if not adequately addressed, could lead to severe strife and even violence. How can we ensure equitable access to these technologies so the world population does not bifurcate into genetic haves and have-nots? Will embryo selection only reinforce our biases, leading to a dangerous human monoculture that undermines our species’ genetic diversity and even long-term survivability? Will we celebrate our children for who they are in a world where technology tempts us to see them as consumer products with optional features? Will selecting for specific traits return us to an age of eugenics, in which the humanity of all is undermined because we fail to recognize the humanity of each?

There are no easy answers to these questions. Grappling with them must be an essential counterpart to the expanding adoption of advanced assisted reproduction technologies. We will need far more significant national and global regulatory authorities and institutions to help frame and implement a popular conversation about the future of our species in an age of revolutionary technology. We’ll have to negotiate effective international agreements that foster the most beneficial uses of these technologies and minimize the likelihood of abuse. All of this will be extremely difficult.

But no matter what we do or do not do, the human species has rounded a corner in our evolutionary process. Embryo selection is only the beginning of this transformation. Our genetically altered future has already begun.