The cruel reality of living through a moment of catastrophic change is that the knowledge of how many other people are also living through it offers no comfort. It is happening to you: Your house is gone. Your father’s paintings are gone. Your hundreds of hours of footage, meant to be your film, gone. Your family’s efforts, across a whole generation, to establish financial stability, literally up in smoke. That this is also happening to other people is awful. As is knowing that it will almost certainly happen again.

Los Angeles is still smoldering. The winds have died down, but the Palisades Fire is just 39 percent contained, and the Eaton Fire is 65 percent. Many residents are under instructions not to drink their tap water, which ash and melted pipes may have contaminated. Tens of thousands of people under evacuation orders are still waiting to return, perhaps to a burned-out lot, or perhaps to a house still standing but coated in the toxic remains of everything around it.

The fires were, at their worst, unfightable. But destruction at this scale was not inevitable. The question now is what measures anyone will take to limit the damage next time.

Because there will be a next fire. The vegetation—fire fuel—will grow back, fire season will keep lengthening into wind season, and the combination of drought and wind will nurse an errant spark. Fire is part of the ecology in California; a century of suppressing it has only set up modern blazes to be more intense.

The way places such as California prepare for these fires has to change, or more neighborhoods will end up in ruins. Insurance is meant to insulate people from bearing the costs of extraordinary events, but those are becoming ordinary enough that private insurers have been leaving California. The state’s FAIR Plan, a pooled insurance plan of last resort, is oversubscribed, and may not be able to cover the claims from these fires alone. If it exercises its power to demand that private insurers help cover the difference, that could send even more fleeing. These are all signs that the state’s magical thinking about fire risk has exhausted itself.

[Read: Are you sure your house is worth that much?]

“California is like a driver that’s had five car accidents,” Michael Wara, a former member of California’s wildfire commission who now heads a climate-and-energy-policy program at Stanford University, told me. The state is at proven risk of catastrophic loss. But because California has spent years trying to keep insurance rates somewhat reasonable, those (still high) rates don’t reflect the real risk homeowners face. This creates a problem further up the insurance food chain: Insurers rely on reinsurers—insurance companies for insurance companies—who, Wara said, “are supposed to lose one in 100 times … They’re not supposed to lose, like, four times out of 10, which is kind of where we’re on track for in California.”

If a few of those companies stop insuring the insurers, there aren’t necessarily others to step in. The state is trying to stave off a reinsurance crisis by allowing insurers to incorporate more risk probability and reinsurance prices into their rates, as of last year. But California could still turn into Florida, where all but the most local insurers are leaving the state, or going belly-up, and insurance in places can cost tens of thousands of dollars a year. Because coverage is generally required for anyone seeking a mortgage, soaring rates in California could drive home values down, threatening yet another crisis, this one in real estate. And if existing homeowners can’t get insurance, they’ll be left bearing the cost of catastrophes all on their own, like many in the burn area around Los Angeles are now.

If nothing changes, more people will get sucked into this doom spiral, because California cannot avoid some level of catastrophe. Wind-driven fires like the ones in L.A. throw embers far ahead of themselves, leading to conflagrations that firefighters can’t stop, and the fastest fires are growing faster now. Transferring those risks to insurance will become less and less affordable as the climate warms and more people live in the zone where cities meet wildlands, because the catastrophic risk to homes is high and getting higher. As Nancy Watkins, an actuary at Milliman who specializes in catastrophic property risk, told me, “That actually is not an insurance problem. It’s a risk problem.”

To bring down risk, she wants to see neighborhoods embark on ambitious missions to “harden” homes and the landscape around them, and then see insurance companies account for those efforts. If each homeowner has removed vegetation from the first five feet around their house, if the neighborhood has kept its roads clear and made firebreaks where fire would be likeliest to enter, a place has much less of a chance of burning down, even in major fires. Plenty of communities, even the most fire-prone ones, still don’t do this. Watkins imagines a future database in which each parcel of land is inspected for fire-readiness, so that each neighborhood can be profiled for fire safety and insurers can price rates accordingly. Creating this system would take major effort, she knows, but it would motivate collective action: If it meant the difference between your whole neighborhood getting insurance and being uninsured, you would probably clean up your yard and screen your vents.

Watkins herself lives in the Moraga-Orinda Fire District, a highly flammable area outside San Francisco, which Wara’s research has identified as one of the top three places where the worst overnight losses could occur, from an insurance perspective. (Another was Pacific Palisades.) She was one of many in her area who got a nonrenewal notice from her insurer last year. Now she’s making her plot as fire-proof as possible, in hopes of coaxing an insurer back. It’s like staging a property for sale, she said: “We’re staging our home for insurability right now.” She cut down a 10-year-old manzanita tree and pulled out her mint garden, but so far she’s kept the Japanese maple that came with the house and turns a brilliant red in the fall. Once she has fire-proofed the rest of the property, she plans to invite a fire-chief friend over for dinner and ask, How bad is the maple? “And then do what they say,” she told me.

But unless her neighbors make similar efforts, Watkins’s risk will still be elevated. And taking these measures can be politically unpopular. Dave Winnacker, who was the fire chief of the Moraga-Orinda Fire District until his retirement last month, told me about trying to pass an ordinance that would require homeowners to keep a five-foot perimeter around their house free of flammable material; the public comments were overwhelmingly in opposition, even though these borders are proved to cut a house’s risk of burning down, he said. Residents called it a draconian overreach that would make their home unsightly and bring down property values. He chose that moment to retire. He didn’t want to be held accountable for their failure to act the next time fire arrived.

When communities do act, it can save them. Crystal Kolden, a pyrogeographer at UC Merced, studied what happened to Montecito, California—the town of Harry and Meghan, and Oprah—after it decided in the 1990s to take fire prevention seriously. From 1999 to 2017, the town spent $1.6 million total clearing brush, maintaining evacuation paths, building fuelbreaks, and working with homeowners to make sure they’d cleared vegetation around their houses. When the Thomas Fire came through in 2017—a worst-case-scenario fire for the region, with wind speeds around 75 miles an hour—Montecito could have lost 450 to 500 homes, Kolden’s research showed. Instead it lost just seven. Yards in Montecito do look a little different from others in California. But “there’s a lot of really gorgeous landscaping that does not burn,” Kolden told me. Succulents and other fire-resistant plants—think giant agaves—can be close to houses; rock gardens can be beautiful. Palm trees are fine if they’re well-manicured enough that they wouldn’t throw off flaming fronds, as some in L.A. did this week.

For a wealthy community such as Montecito, less than $2 million across almost 20 years is by no means prohibitively expensive. And according to Wara’s research, the state could help fund projects like these at relatively low cost. By spending about $3 billion a year—less than Cal Fire’s total fire-suppression budget in 2020, by his calculation—the state could harden about 100,000 homes a year, starting in the most fire-prone areas, and build fuelbreaks in every highly threatened community. That would also cover preventive burns on every acre that needs them, to prevent larger fires later.

Of course, landscaping and building better-sealed homes won’t change the fact that the biggest California fires are getting more intense. Climate change is creating more suitable conditions for the worst conflagrations to arise, and they will, again and again, with greater frequency now. Slowing that trajectory is a matter of global action. But yet here Angelenos are, living at the scale of their homes, their parcels of the Earth. Fires in California are like hurricanes in Florida. They’re going to happen, and people will live in their path. Stopping them from happening is impossible. But minimizing the damage they wreak is not.

Here’s a simple question: Is moderate drinking okay?

Like millions of Americans, I look forward to a glass of wine—sure, occasionally two—while cooking or eating dinner. I strongly believe that an ice-cold pilsner on a hot summer day is, to paraphrase Benjamin Franklin, suggestive evidence that a divine spirit exists and gets a kick out of seeing us buzzed.

But, like most people, I understand that booze isn’t medicine. I don’t consider a bottle of California cabernet to be the equivalent of a liquid statin. Drinking to excess is dangerous for our bodies and those around us. Having more than three or four drinks a night is strongly related to a host of diseases, including liver cirrhosis, and alcohol addiction is a scourge for those genetically predisposed to dependency.

If the evidence against heavy drinking is clear, the research on my wine-with-dinner habit is a wasteland of confusion and contradiction. This month, the U.S. surgeon general published a new recommendation that all alcohol come with a warning label indicating it increases the risk of cancer. Around the same time, a meta-analysis published by the National Academies of Sciences, Engineering, and Medicine concluded that moderate alcohol drinking is associated with a longer life. Many scientists scoffed at both of these headlines, claiming that the underlying studies are so flawed that to derive strong conclusions from them would be like trying to make a fine wine out of a bunch of supermarket grapes.

I’ve spent the past few weeks poring over studies, meta-analyses, and commentaries. I’ve crashed my web browser with an oversupply of research-paper tabs. I’ve spoken with researchers and then consulted with other scientists who disagreed with those researchers. And I’ve reached two conclusions. First, my seemingly simple question about moderate drinking may not have a simple answer. Second, I’m not making any plans to give up my nightly glass of wine.

Alcohol ambivalence has been with us for almost as long as alcohol. The notion that booze is enjoyable in small doses and hellish in excess was captured well by Eubulus, a Greek comic poet of the fourth century B.C.E., who wrote that although two bowls of wine brought “love and pleasure,” five led to “shouting,” nine led to “bile,” and 10 produced outright “madness, in that it makes people throw things.”

In the late 20th century, however, conventional wisdom lurched strongly toward the idea that moderate drinking was healthy, especially when the beverage of choice was red wine. In 1991, Morley Safer, a correspondent for CBS, recorded a segment of 60 Minutes titled “The French Paradox,” in which he pointed out that the French filled their stomachs with meat, oil, butter, and other sources of fat, yet managed to live long lives with lower rates of cardiovascular disease than their Northern European peers. “The answer to the riddle, the explanation of the paradox, may lie in this inviting glass” of red wine, Safer told viewers. Following the report, demand for red wine in the U.S. surged.

[Read: America has a drinking problem]

The notion that a glass of red wine every night is akin to medicine wasn’t just embraced by a gullible news media. It was assumed as a matter of scientific fact by many researchers. “The evidence amassed is sufficient to bracket skeptics of alcohol’s protective effects with the doubters of manned lunar landings and members of the flat-Earth society,” the behavioral psychologist and health researcher Tim Stockwell wrote in 2000.

Today, however, Stockwell is himself a flat-earther, so to speak. In the past 25 years, he has spent, he told me, “thousands and thousands of hours” reevaluating studies on alcohol and health. And now he’s convinced, as many other scientists are, that the supposed health benefits of moderate drinking were based on bad research and confounded variables.

A technical term for the so-called French paradox is the “J curve.” When you plot the number of drinks people consume along an X axis and their risk of dying along the Y axis, most observational studies show a shallow dip at about one drink a day for women and two drinks a day for men, suggesting protection against all-cause mortality. Then the line rises—and rises and rises—confirming the idea that excessive drinking is plainly unhealthy. The resulting graph looks like a J, hence the name.

The J-curve thesis suffers from many problems, Stockwell told me. It relies on faulty comparisons between moderate drinkers and nondrinkers. Moderate drinkers tend to be richer, healthier, and more social, while nondrinkers are a motley group that includes people who have never had alcohol (who tend to be poorer), people who quit drinking alcohol because they’re sick, and even recovering alcoholics. In short, many moderate drinkers are healthy for reasons that have nothing to do with drinking, and many nondrinkers are less healthy for reasons that have nothing to do with alcohol abstention.

[Read: Not just sober-curious, but neo-temperate]

When Stockwell and his fellow researchers threw out the observational studies that were beyond salvation and adjusted the rest to account for some of the confounders I listed above, “the J curve disappeared,” he told me. By some interpretations, even a small amount of alcohol—as little as three drinks a week—seemed to increase the risk of cancer and death.

The demise of the J curve is profoundly affecting public-health guidance. In 2011, Canada’s public-health agencies said that men could safely enjoy up to three oversize drinks a night with two abstinent days a week—about 15 drinks a week. In 2023, the Canadian Centre on Substance Use and Addiction revised its guidelines to define low-risk drinking as no more than two drinks a week.

Here’s my concern: The end of the J curve has made way for a new emerging conventional wisdom—that moderate drinking is seriously risky—that is also built on flawed studies and potentially overconfident conclusions. The pendulum is swinging from flawed “red wine is basically heart medicine!” TV segments to questionable warnings about the risk of moderate drinking and cancer. After all, we’re still dealing with observational studies that struggle to account for the differences between diverse groups.

[Read: Is a glass of wine harmless? Wrong question.]

In a widely read breakdown of alcohol-health research, the scientist and author Vinay Prasad wrote that the observational research on which scientists are still basing their conclusions suffers from a litany of “old data, shitty data, confounded data, weak definitions, measurement error, multiplicity, time-zero problems, and illogical results.” As he memorably summarized the problem: “A meta-analysis is like a juicer, it only tastes as good as what you put in.” Even folks like Stockwell who are trying to turn the flawed data into useful reviews are like well-meaning chefs, toiling in the kitchen, doing their best to make coq au vin out of a lot of chicken droppings.

The U.S. surgeon general’s new report on alcohol recommended adding a more “prominent” warning label on all alcoholic beverages about cancer risks. The top-line findings were startling. Alcohol contributes to about 100,000 cancer cases and 20,000 cancer deaths each year, the surgeon general said. The guiding motivation sounded honorable. About three-fourths of adults drink once or more a week, and fewer than half of them are aware of the relationship between alcohol and cancer risk.

But many studies linking alcohol to cancer risk are bedeviled by the confounding problems facing many observational studies. For example, a study can find a relationship between moderate alcohol consumption and breast-cancer detection, but moderate consumption is correlated with income, as is access to mammograms.

One of the best-established mechanisms for alcohol being related to cancer is that alcohol breaks down into acetaldehyde in the body, which binds to and damages DNA, increasing the risk that a new cell grows out of control and becomes a cancerous tumor. This mechanism has been demonstrated in animal studies. But, as Prasad points out, we don’t approve drugs based on animal studies alone; many drugs work in mice and fail in clinical trials in humans. Just because we observe a biological mechanism in mice doesn’t mean you should live your life based on the assumption that the same cellular dance is happening inside your body.

[Read: The truth about breast cancer and drinking red wine—or any alcohol]

I’m willing to believe, even in the absence of slam-dunk evidence, that alcohol increases the risk of developing certain types of cancer for certain people. But as the surgeon general’s report itself points out, it’s important to distinguish between “absolute” and “relative” risk. Owning a swimming pool dramatically increases the relative risk that somebody in the house will drown, but the absolute risk of drowning in your backyard swimming pool is blessedly low. In a similar way, some analyses have concluded that even moderate drinking can increase a person’s odds of getting mouth cancer by about 40 percent. But given that the lifetime absolute risk of developing mouth cancer is less than 1 percent, this means one drink a day increases the typical individual’s chance of developing mouth cancer by about 0.3 percentage points. The surgeon general reports that moderate drinking (say, one drink a night) increases the relative risk of breast cancer by 10 percent, but that merely raises the absolute lifetime risk of getting breast cancer from about 11 percent to about 13 percent. Assuming that the math is sound, I think that’s a good thing to know. But if you pass this information along to a friend, I think you can forgive them for saying: Sorry, I like my chardonnay more than I like your two percentage points with a low confidence interval.

Where does this leave us? Not so far from our ancient-Greek friend Eubulus. Thousands of years and hundreds of studies after the Greek poet observed the dubious benefits of too much wine, we have much more data without much more certainty.

In her review of the literature, the economist Emily Oster concluded that “alcohol isn’t especially good for your health.” I think she’s probably right. But life isn’t—or, at least, shouldn’t be—about avoiding every activity with a whisker of risk. Cookies are not good for your health, either, as Oster points out, but only the grouchiest doctors will instruct their healthy patients to foreswear Oreos. Even salubrious activities—trying to bench your bodyweight, getting in a car to hang out with a friend—incur the real possibility of injury.

[Read: A daily drink is almost certainly not going to hurt you]

An appreciation for uncertainty is nice, but it’s not very memorable. I wanted a takeaway about alcohol and health that I could repeat to a friend if they ever ask me to summarize this article in a sentence. So I pressed Tim Stockwell to define his most cautious conclusions in a memorable way, even if I thought he might be overconfident in his caution.

“One drink a day for men or women will reduce your life expectancy on average by about three months,” he said. Moderate drinkers should have in their mind that “every drink reduces your expected longevity by about five minutes.” (The risk compounds for heavier drinkers, he added. “If you drink at a heavier level, two or three drinks a day, that goes up to like 10, 15, 20 minutes per drink—not per drinking day, but per drink.”)

Every drink takes five minutes off your life. Maybe the thought scares you. Personally, I find great comfort in it—even as I suspect it suffers from the same flaws that plague this entire field. Several months ago, I spoke with the Stanford University scientist Euan Ashley, who studies the cellular effects of exercise. He has concluded that every minute of exercise adds five extra minutes of life.

When you put these two statistics together, you get this wonderful bit of rough longevity arithmetic: For moderate drinkers, every drink reduces your life by the same five minutes that one minute of exercise can add back. There’s a motto for healthy moderation: Have a drink? Have a jog.

Even this kind of arithmetic can miss a bigger point. To reduce our existence to a mere game of minutes gained and lost is to squeeze the life out of life. Alcohol is not like a vitamin or pill that we swiftly consume in the solitude of our bathrooms, which can be straightforwardly evaluated in controlled laboratory testing. At best, moderate alcohol consumption is enmeshed in activities that we share with other people: cooking, dinners, parties, celebrations, rituals, get-togethers—life! It is pleasure, and it is people. It is a social mortar for our age of social isolation.

[Read: The anti-social century]

An underrated aspect of the surgeon general’s report is that it is following, rather than trailblazing, a national shift away from alcohol. As recently as 2005, Americans were more likely to say that alcohol was good for their health, instead of bad. Last year, they were more than five times as likely to say it was bad, instead of good. In the first seven months of 2024, alcohol sales volume declined for beer, wine, and spirits. The decline seemed especially pronounced among young people.

To the extent that alcohol carries a serious risk of excess and addiction, less booze in America seems purely positive. But for those without religious or personal objections, healthy drinking is social drinking, and the decline of alcohol seems related to the fact that Americans now spend less time in face-to-face socializing than any period in modern history. That some Americans are trading the blurry haze of intoxication for the crystal clarity of sobriety is a blessing for their minds and guts. But in some cases, they may be trading an ancient drug of socialization for the novel intoxicants of isolation.

The first time Jamie Cassidy was pregnant, the fetus had a genetic mutation so devastating that she and her husband, Brennan, decided to terminate in the second trimester. The next time they tried for a baby, they weren’t taking chances: They would use IVF and screen their embryos’ DNA. They wanted to avoid transferring any embryos with the single-gene mutation that had doomed their first pregnancy. And then they started wondering what other ailments they could save their future son or daughter from.

The Cassidys’ doctor told them about a company, Genomic Prediction, that could assess their potential children’s odds of developing conditions that aren’t tied to a single gene, such as heart disease, diabetes, and schizophrenia. The test wouldn’t be any more invasive than screening for a single gene—all the company needed was an embryo biopsy. The science is still in its early stages, but the Cassidys didn’t mind. Brennan has Type 1 diabetes and didn’t want to pass that condition on, either. “If I can forecast that my baby is going to have less chance to have Type 1 diabetes than I did, I want that,” he told me. “I’d burn all my money to know that.”

Thanks to more sophisticated genetic-testing techniques, IVF—an expensive, invasive treatment originally developed to help people with fertility troubles—is becoming a tool for optimizing health. A handful of companies offer screening for diseases and disorders that range from life-threatening (cancer) to life-altering (celiac disease). In many cases, these conditions’ genetic links are poorly understood or weak, just one factor of many that determine whether a person develops a particular condition. But bringing another human being into the universe can be a terrifying-enough prospect that some parents are turning to extensive genetic testing to help pick their future offspring.

Genetic screening has been a crucial part of IVF—and pregnancy—for decades. Medical guidelines recommend that any aspiring mother should be given the option to test her own DNA and find out whether she risks passing on dangerous genes, a practice known as carrier screening. If both parents carry a particular mutation, doctors will likely suggest IVF and embryo screening. These measures are traditionally limited to conditions linked to single-gene mutations, such as Huntington’s disease, most of which are exceedingly rare and seriously affect a child’s quality of life. During IVF, embryos are also typically screened for chromosomal abnormalities to help avoid miscarriages, and generally nonheritable conditions such as Down syndrome.

[Read: Genetic discrimination is coming for us all]

As the scientific understanding of the genome has progressed, companies including Genomic Prediction and a competitor called Orchid have begun offering a test that promises a more comprehensive investigation of the risks lurking in an embryo's genes, using what’s known as a polygenic risk score. Most common ailments aren’t connected to a single gene; polygenic risk scores aim to predict the lifetime likelihood of conditions, such as diabetes, in which many genes contribute to a person’s risk. Consumer DNA-testing companies such as 23andMe use these scores to tell customers whether they have, say, a slightly above-average likelihood of developing celiac disease, along with a disclaimer that lifestyle and other factors can also influence their chances. These risk scores could theoretically help identify customers who, say, need a colonoscopy earlier in life, or who need to double down on that New Year’s resolution to eat healthier. But the current scientific consensus is that polygenic risk scores can’t yet provide useful insights into a person’s health, if indeed they ever will.  

Analyzing an embryo’s DNA to predict its chances of developing genetically complex conditions such as diabetes is an even thornier issue. The tests, which can run thousands of dollars and are typically not covered by insurance, involve sending a small sample of the embryos to the companies’ labs. In the United States, such tests don’t need to be approved by the FDA. Genomic Prediction even offers customers an assessment of which embryos are “healthiest” overall. But the control these services offer is an illusion, like promising to predict the weather a year in advance, Robert Klitzman, a Columbia University bioethicist and the author of the book Designing Babies, told me. A spokesperson for the American Society for Reproductive Medicine told me there aren’t enough quality data to even take a position on whether such tests are useful. And last year, the American College of Medical Genetics and Genomics published a lengthy position statement concluding that the benefits of screening embryos for polygenic risk were “unproven” and that the tests “should not be offered as a clinical service.” The statement raised the possibility that people might undergo extra, unnecessary rounds of IVF in search of ever healthier embryos.

Genomic Prediction published a rebuttal to the ACMG that cited, among other research, several studies led by company researchers that concluded that among siblings, those with a lower risk score were significantly less likely to have a given condition. The truth is, though, the effect of screening embryos for polygenic risk won’t be clear until the embryos chosen to develop into fetuses are born, grow up, and either develop diabetes or don’t. Genomic Prediction and Orchid both told me that humanity shouldn’t have to wait that long for the insights their tests provide. Polygenic risk scores are “one of the most valuable pieces of information that you can get,” Orchid’s founder and CEO, Noor Siddiqui, told me. Nathan Treff, Genomic Prediction’s chief science officer, was similarly bullish. “Everybody has some kind of family history of diabetes, cancer, and heart disease. So we really don’t have a situation where there’s no reason for testing,” he told me.

Many of the experts I spoke with about these tests are concerned that people might opt into IVF because they’re chasing certainty that companies can’t really promise. A study last year found both high interest and approval among Americans when it comes to screening embryos for polygenic risk. For now, most of the customers I interviewed used advanced tests that included polygenic risk because they were going through IVF anyway. Many of Genomic Prediction’s customers using the scores are participants in a clinical trial. But Tara Harandi-Zadeh, an investor in Orchid, told me she planned to do IVF even though she and her husband have no fertility issues or history of genetic disease. Harandi-Zadeh is especially worried about de novo mutations—genetic changes that occur spontaneously, without any hereditary link. She wants to screen her embryos to weed out monogenic diseases and plan for the risks of polygenic ones. “If I have that information, I can help my child at the stages of life to be able to get treatment or tests or just prepare for it,” she said. Treff told me that people like Harandi-Zadeh make up a small percentage of Genomic Prediction’s customers, but their numbers are growing.

[Emi Nietfeld: America’s IVF failure]

Scientists just don’t understand enough about the genome to confidently predict what any single embryo will be like should it go on to become a person. Most genes influence many facets of our being—our health, our physical traits, our personality—and only a fraction of those interactions have been investigated. “You don’t know the full package,” Klitzman said. “Bipolar disorder is associated with creativity. So if you screen out bipolar disorder, you may also be screening out genes for creativity, for instance.” Because no embryo is completely risk-free, future parents might also have to decide whether they think, say, a risk of diabetes or a risk of heart disease sounds worse. A paper out last week put it this way: “The expected reductions in disease risk are modest, at best—even if the clinical, ethical and social concerns are dismissed.”

Those concerns are significant. More and more people are already turning to IVF for reasons other than infertility. Some select their children based on sex. Jeffrey Steinberg, a fertility doctor with clinics in the U.S. and internationally, offers eye color selection and told me he is working on height. Orchid assesses genetic risk for some autism-spectrum disorders, and Genomic Prediction plans to add a similar screening to its catalog. A paper published last week argued that editing embryos—not just testing them—could mitigate genetic risk for a variety of conditions, while also acknowledging it could “deepen health inequalities.” (In the U.S., clinical trials of embryo editing cannot be approved by the FDA, and public funds cannot be used for research in which embryos are edited.) Critics say that even if technology could cut the prevalence of diseases like diabetes, doing so could drive discrimination against those born with such “undesirable” traits. Social services and support for people with those conditions could also erode—similar concerns have been raised, for example, in Iceland, where pregnancy screenings have all but eliminated Down-syndrome births.

[From the December 2020 issue: The last children of Down syndrome]

Even if the science does catch up to the ambitions of companies like Genomic Prediction, genetics will never guarantee a child a healthy life. “Of the 100 things that could go wrong with your baby, 90 percent of them or more are not genetic,” Hank Greely, the director of the Center for Law and the Biosciences at Stanford University, told me. That’s partly why the Cassidys decided to ignore most of their screening results and simply select the embryo that didn’t have the monogenic mutation that Jamie carried, and had the lowest risk of diabetes. “We’re not trying to have a kid that’s 6 foot 2 and blond hair and blue eyes and going to go to Harvard. We just want a healthy baby,” Brennan told me.

Their son was born in 2023 and so far has been at the top of the curve for every developmental marker: He’s big and tall; he talked and walked early. It will be years, probably, before they know whether or not he’s diabetic. But it’s hard, they said, not to feel that they picked the right embryo.