Saber-toothed kittens were born armed to pounce

Saber-toothed kittens were the spitting image of their parents. Even as babies, the cats not only had the oversized canine teeth but also unusually powerful forelimbs, Katherine Long, a graduate student at California State Polytechnic University in Pomona, and colleagues report September 27 in PLOS ONE.

As adults, the ferocious felines used those strong forelimbs to secure wriggling prey before slashing a throat or belly (thereby avoiding breaking off a tooth in the struggle). Paleontologists have puzzled over whether saber-toothed cats such as Smilodon fatalis developed those robust limbs as they grew.

To compare the growth rate of Smilodon with that of similar-sized non‒saber-toothed cats that lived alongside it, Long and her team turned to fossils collected from the La Brea Tar Pits in Los Angeles. The ancient asphalt traps hold a wealth of species and specimens from juveniles to adults, dating to between 37,000 and 9,000 years ago.

The Smilodon bones, they found, did not show any evidence of an unusual growth spurt. Instead, the bones grew longer and slimmer as the kittens grew up, following the same developmental pattern as the other large cats. That suggests that when it comes to their mighty forelimbs, Smilodon kittens were just born that way.

Christina Warinner uncovers ancient tales in dental plaque

In a pitch-black rainforest with fluttering moths and crawling centipedes, Christina Warinner dug up her first skeleton. Well, technically it was a full skeleton plus two headless ones, all seated and draped in ornate jewelry. To deter looters, she excavated through the night while one teammate held up a light and another killed as many bugs as possible.

As Warinner worked, unanswerable questions about the people whose skeletons she was excavating flew through her mind. “There’s only so much you can learn by looking with your own eyes at a skeleton,” she says. “I became increasingly interested in all the things that I could not see — all the stories that these skeletons had to tell that weren’t immediately accessible, but could be accessible through science.”

At age 21, Warinner cut her teeth on that incredibly complex sacrificial burial left behind by the Maya in a Belize rainforest. Today, at age 37, the molecular anthropologist scrapes at not-so-pearly whites to investigate similar questions, splitting her time between the University of Oklahoma in Norman and the Max Planck Institute for the Science of Human History in Jena, Germany.
In 2014, she and colleagues reported a finding that generated enough buzz to renew interest in an archaeological resource many had written off decades ago: fossilized dental plaque, or calculus. Ancient DNA and proteins in the plaque belong to microbes that could spill the secrets of the humans they once inhabited — what the people ate, what ailed them, perhaps even what they did for a living.

Bacteria form plaque that mineralizes into calculus throughout a person’s life. “It’s the only part of your body that fossilizes while you’re still alive,” notes Warinner. “It’s also the last thing to decay.”

Though plaque is prolific in the archaeological record, most researchers viewed calculus as “the crap you scraped off your tooth in order to study it,” says Amanda Henry, an archaeologist at Leiden University in the Netherlands. With some exceptions, molecular biologists saw calculus as a shoddy source of ancient DNA.

But a few researchers, including Henry, had been looking at calculus for remnants of foods as potential clues to ancient diets. Inspired by some of Henry’s images of starch grains preserved in calculus, Warinner wondered if the plaque might yield dead bacterial structures, perhaps even bacteria’s genetic blueprints.

Her timing couldn’t have been better. Warinner began her graduate studies at Harvard in 2004, just after the sequencing of the human genome was completed and by the time she left in 2010, efforts to survey the human microbiome were in full swing. As a postdoc at the University of Zurich, Warinner decided to attempt to extract DNA from the underappreciated dental grime preserved on the teeth of four medieval skeletons from Germany.
At first, the results were dismal. But she kept at it. “Tina has a very interested, curious and driven personality,” Henry notes. Warinner turned to a new instrument that could measure DNA concentrations in skimpy samples, a Qubit fluorometer. A surprising error message appeared: DNA too high. Dental calculus, it turned out, was chock-full of genetic material. “While people were struggling to pull out human DNA from the skeleton itself, there’s 100 to 1,000 times more DNA in the calculus,” Warinner says. “It was sitting there in almost every skeletal collection untouched, unanalyzed.”
To help her interpret the data, Warinner mustered an army of collaborators from fields ranging from immunology to metagenomics. She and her colleagues found a slew of proteins and DNA snippets from bacteria, viruses and fungi, including dozens of oral pathogens, as well as the full genetic blueprint of an ancient strain of Tannerella forsythia, which still infects people’s gums today. In 2014, Warinner’s team revealed a detailed map of a miniature microbial world on the decaying teeth of those German skeletons in Nature Genetics.

Later in 2014, her group found the first direct protein-based evidence of milk consumption in the plaque of Bronze Age skeletons from 3000 B.C. That same study linked milk proteins preserved in the calculus of other ancient human skeletons to specific animals — providing a peek into long-ago lifestyles.

“The fact that you can tell the difference between, say, goat milk and cow milk, that’s kind of mind-blowing,” says Laura Weyrich, a microbiologist at the University of Adelaide in Australia, who also studies calculus.
Since then, Warinner has found all sorts of odds and ends lurking on archaic chompers from poppy seeds to paint pigments. Warinner’s team is still looking at the origins of dairying and its microbial players, but she’s also branching out to the other end of the digestive spectrum. The researchers are looking at ancient DNA in paleofeces, which is exactly what it sounds like — desiccated or semifossilized poop. It doesn’t stay as fresh as plaque in the archaeological record. But she’s managed to find some sites with well-preserved samples. By examining the array of microbes that lived in the excrement and plaque of past humans and their relatives, Warinner hopes to characterize how our microbial communities have changed through time — and how they’ve changed us.

The research has implications for understanding chronic, complex human diseases over time. Warinner’s ancient DNA work “opens up a window on past health,” says Clark Larsen, an anthropologist at Ohio State University.

It’s all part of what Warinner calls “the archaeology of the unseen.”

Editor’s note: This story was corrected on October 4, 2017, to note that the 2014 report on milk consumption was based on protein evidence, not DNA.

Economics Nobel nudges behavioral economist into the limelight

A founding father of behavioral economics — a research school that has popularized the practice of “nudging” people into making decisions that authorities deem to be in their best interests — has won the 2017 Nobel Memorial Prize in Economic Sciences.

Richard Thaler, of the University of Chicago Booth School of Business, received the award October 9 for being the leader of a discipline that has championed the idea of humans not as purely rational and selfish — as long posited by economists. Instead, he argues, we are driven by simple, often emotionally fueled assumptions that can lead us astray.

“Richard Thaler has pioneered the analysis of ways in which human decisions systematically deviate from traditional economic models,” says cognitive scientist Peter Gӓrdenfors of Lund University, Sweden, a member of the Economic Sciences Prize Committee.

Thaler argues that, even if people try to make good economic choices, our thinking abilities are limited. In dealing with personal finances, for instance, he finds that most people mentally earmark money into different accounts, say for housing, food, vacations and entertainment. That can lead to questionable decisions, such as saving for a vacation in a low-interest savings account while buying household goods with a high-interest credit card.

At an October 9 news conference at the University of Chicago, Thaler referenced mental accounting in describing what he would do with the roughly $1.1 million award. “Every time I spend any money on something fun, I’ll say it came from the Nobel Prize.”

Thaler’s research has also focused on how judgments about fairness, such as sudden jumps in the prices of consumer items, affect people’s willingness to buy those items. A third area of his research finds that people’s short-term desires often override long-term plans. A classic example consists of putting off saving for retirement until later in life.

That research in particular inspired his 2008 book Nudge: Improving Decisions about Health, Wealth and Happiness, coauthored by Cass Sunstein, now at Harvard Law School. Nudging, also known as libertarian paternalism, is a way for public and private institutions to prod people to make certain decisions (SN: 3/18/17, p. 18). For instance, employees more often start saving for retirement early in their careers when offered savings plans that they must opt out of.
Many governments, including those of the United Kingdom and the United States, have funded teams of behavioral economists, called nudge units, to develop ways to nudge people to, say, apply for government benefits or comply with tax laws. A total of 75 nudge units now exist worldwide, Thaler said at the news conference.

Nudging has its roots in a line of research, dubbed heuristics and biases, launched in the 1970s by two psychologists — 2002 economics Nobel laureate Daniel Kahneman of Princeton University and the late Amos Tversky of Stanford University. Investigators in heuristics and biases contend that people can’t help but make many types of systematic thinking errors, such as being overconfident in their decisions.

Thaler, like Kahneman, views the mind as consisting of one system for making rapid, intuitive decisions that are often misleading and a second system for deliberating slowly and considering as much relevant information as possible.

Despite the influence of Thaler’s ideas on research and social policy, they are controversial among decision researchers (SN: 6/4/11, p. 26). Some argue that nudging overlooks the power of simple rules-of-thumb for making decisions that people can learn to wield on their own.

“I don’t think I’ve changed everybody’s minds,” Thaler said. “But many young economists embrace behavioral economics.”

This stretchy implant could help kids avoid repeated open-heart surgeries

A new stretchy prosthetic could reduce the number of surgeries that children with leaking heart valves must undergo.

The device, a horseshoe-shaped implant that wraps around the base of a heart valve to keep it from leaking, is described online October 10 in Nature Biomedical Engineering. In adults, a rigid ring is used, but it can’t be implanted in children because it would constrict their natural heart growth. Instead, pediatric surgeons cinch their patients’ heart valves with stitches — which can break or pull through tissue as a child grows, requiring further surgery to repair.
It’s not uncommon for a child to require two to four of these follow-up procedures, says study coauthor Eric Feins, a cardiac surgeon at Boston Children’s Hospital and Harvard Medical School. Doctors in the United States perform over 1,000 pediatric heart valve repair surgeries each year.

“It’s quite invasive to do surgeries on a beating heart,” says coauthor Jeff Karp, a biomedical engineer at Brigham and Women’s Hospital in Boston. To decrease the need for these open-heart follow-up procedures, Karp and colleagues invented a new type of implant that stretches as its wearer grows. It’s made of a biodegradable polyester core covered by a mesh tube. The material of this outer sleeve is interwoven like a Chinese finger trap, so when heart valve tissue grows and tugs on the tube’s ends, it stretches. Over time, the core dissolves, and the growing tissue can pull the sleeve into a longer, thinner shape.
By tweaking an implant’s initial length and width, the core’s chemical makeup and the tightness of the sleeve’s braid, the researchers can fine-tune the stretchiness. This could allow developers to tailor each device to accommodate an individual patient’s expected growth rate.

“This is a brand new idea. I’ve never seen anything like it before,” says Gus Vlahakes, a cardiac surgeon at Massachusetts General Hospital in Boston, who was not involved in the study. “It’s a great concept.”
Karp and colleagues tested prototypes of the heart implant by inserting them into growing piglets. Twenty weeks after surgery, the implants had expanded as expected. The biomedical device company CryoLife, Inc. is now using the researchers’ design to build ring implants for further studies in lab animals, Karp says. “Clinical trials could start within a few years, if all goes well,” he says.

This growth-accommodating design may also be repurposed to make other kinds of pediatric implants. For instance, stretchable devices could supplant the stiff plates and staples that surgeons currently use to treat bone growth disorders. The researchers’ new implant model is “very generalizable,” Vlahakes says.

Jupiter’s lightning bolts contort the same way as Earth’s

On Jupiter, lightning jerks and jolts a lot like it does on Earth.

Jovian lightning emits radio wave pulses that are typically separated by about one millisecond, researchers report May 23 in Nature Communications. The energetic prestissimo, the scientists say, is a sign that the gas giant’s lightning propagates in pulses, at a pace comparable to that of the bolts that cavort through our own planet’s thunderclouds. The similarities between the two world’s electrical phenomena could have implications for the search for alien life.
Arcs of lightning on both worlds appear to move somewhat like a winded hiker going up a mountain, pausing after each step to catch their breath, says Ivana Kolmašová, an atmospheric physicist at the Czech Academy of Sciences in Prague. “One step, another step, then another step … and so on.”

Here on Earth, lightning forms as turbulent winds within thunderclouds cause many ice crystals and water droplets to rub together, become charged and then move to opposite sides of the clouds, progressively generating static electrical charges. When the charges grow big enough to overcome the air’s ability to insulate them, electrons are released — the lightning takes its first step. From there, the surging electrons will repeatedly ionize the air and rush into it, lurching the bolt forward at an average of hundreds of thousands of meters per second.

Scientists have suggested that superbolts observed in Jovian clouds might also form by collisions between ice crystals and water droplets (SN: 8/5/20). But no one knew whether the alien bolts extended and branched in increments, as they do on Earth, or if they took some other form.

For the new study, Kolmašová and her colleagues used five years of radio wave data collected by NASA’s Juno spacecraft (SN: 12/15/22). Analyzing hundreds of thousands of radio wave snapshots, the team found radio wave emissions from Jovian lightning appeared to pulse at a rate comparable to that of Earth’s intracloud lightning — arcs of electricity that never strike ground.

If bolts extend through Jupiter’s water clouds at a similar velocity as they do in Earth’s clouds, then Jovian lightning might branch and extend in steps that are hundreds to thousands of meters long. That’s comparable in length to the jolted strides of Earth’s intracloud lightning, the researchers say.

“That’s a perfectly reasonable explanation,” says atmospheric physicist Richard Sonnenfeld of the New Mexico Institute of Mining and Technology in Socorro, who wasn’t involved in the study. Alternatively, he says, the signals could be produced as pulses of electrical current propagate back and forth along tendrils of lightning that have already formed, rather than from the stop-and-go advancements of a new bolt. On Earth, such currents cause some bolts to appear to flicker.

But stop and go seems like a sound interpretation, says atmospheric physicist Yoav Yair of Reichman University in Herzliya, Israel. Kolmašová and her colleagues “show that if you’re discharging a cloud … the physics remains basically the same [on Jupiter as on Earth], and the current will behave the same.”

If that universality is real, it could have implications for the search for life elsewhere. Experiments have shown that lightning strikes on Earth could have smelted some of the chemical ingredients needed to form the building blocks of life (SN: 3/16/21). If lightning is discharging in a similar way on alien worlds, Yair says, then it could be producing similar ingredients in those places too.

A quake on Mars showed its crust is thicker than Earth’s

Planetary scientists now know how thick the Martian crust is, thanks to the strongest Marsquake ever observed.

On average, the crust is between 42 and 56 kilometers thick, researchers report in a paper to appear in Geophysical Research Letters. That’s roughly 70 percent thicker than the average continental crust on Earth.

The measurement was based on data from NASA’s InSight lander, a stationary seismometer that recorded waves rippling through Mars’ interior for four Earth years. Last May, the entire planet shook with a magnitude 4.7 quake that lasted more than six hours (SN: 5/13/22). “We were really fortunate that we got this quake,” says seismologist Doyeon Kim of ETH Zurich.
InSight recorded seismic waves from the quake that circled Mars up to three times. That let Kim and colleagues infer the crust thickness over the whole planet.

Not only is the crust thicker than that of the Earth and the moon, but it’s also inconsistent across the Red Planet, the team found. And that might explain a known north-south elevation difference on Mars.

Topological and gravity data from Mars orbiters have shown that the planet’s northern hemisphere is substantially lower than the southern one. Researchers had suspected that density might play a part: Perhaps the rocks that make up northern Mars have a different density than those of southern Mars.

But the crust is thinner in the northern hemisphere, Kim and colleagues found, so the rocks in both hemispheres probably have the same average densities. That finding helps scientists narrow down the explanations for why the difference exists in the first place.

Knowing the crust’s depth, the team also calculated that much of Mars’ internal heat probably originates in the crust. Most of this heat comes from radioactive elements such as potassium, uranium and thorium. An estimated 50 to 70 percent of those elements are probably in the crust rather than the underlying mantle, computer simulations suggest. That supports the idea that parts of Mars still have volcanic activity, contrary to a long-held belief that the Red Planet is dead (SN: 11/3/22).

New dinosaur sported a curious set of chompers

An ancient vegetarian dinosaur from the French countryside has given paleontologists something to sink their teeth into.

The most striking feature of a new species of rhabdodontid that lived from 84 million to 72 million years ago is its oversized, scissorslike teeth, paleontologist Pascal Godefroit, of the Royal Belgian Institute of Natural Sciences in Brussels, and his colleagues report October 26 in Scientific Reports. Compared with other dinos of its kind, Matheronodon provincialis’ teeth were at least twice as large but fewer in number. Some teeth reached up to 6 centimeters long, while others grew up to 5 centimeters wide. They looked like a caricature of normal rhabdodontid teeth, Godefroit says.
Of hundreds of fossils unearthed over the last two decades at a site called Velaux-La Bastide Neuve in the French countryside, a handful of jaw bones and teeth now have been linked to this new species, Matheronodon provincialis. The toothy dino belongs to a group of herbivorous, bipedal dinosaurs common in the Cretaceous Period. Rhabdodontids sported bladelike teeth, and likely noshed on the tough woody tissue parts of plants. Palm trees, common in Europe at the time, might have been on the menu.

Rhabdodontid teeth have ridges covered by a thick layer of enamel on one side and little to no ridges or enamel on the other. Teeth in the upper jaw have more ridges and enamel on the outer edge, while the reverse is true for bottom teeth. A closer look at the microstructure of M. provincialis’ teeth revealed an exaggerated version of this — many more ridges and lopsided enamel coating. Enamel typically protects from wear and tear, so chewing would have sharpened the dino’s teeth. “They operated like self-sharpening serrated scissors,” Godefroit says.

This deep-sea fish uses weird eyes to see in dark and light

Light-sensitive cells in the eyes of some fish do double-duty. In pearlsides, cells that look like rods — the stars of low-light vision — actually act more like cones, which only respond to brighter light, researchers report November 8 in Science Advances. It’s probably an adaptation to give the deep-sea fish acute vision at dawn and dusk, when they come to the surface of the water to feed.

Rods and cones studding the retina can work in tandem to give an animal good vision in a wide variety of light conditions. Some species that live in dark environments, like many deep-sea fish, have dropped cones entirely. But pearlside eyes have confused scientists: The shimmery fish snack at the water’s surface at dusk and dawn, catching more sun than fish that feed at night. Most animals active at these times of day use a mixture of rods and cones to see, but pearlside eyes appear to contain only rods.
“That’s actually not the case when you look at it in more detail,” says study coauthor Fanny de Busserolles, a sensory biologist at the University of Queensland in Australia.

She and her colleagues investigated which light-responsive genes those rod-shaped cells were turning on. The cells were making light-sensitive proteins usually found in cones, the researchers found, rather than the rod-specific versions of those proteins.

These rodlike cones still have the more elongated shape of a rod. And like regular rods, they are sensitive to even small amounts of light. But the light-absorbing proteins inside match those found in cones, and are specifically tuned to respond to the blue wavelengths of light that dominate at dawn and dusk, the researchers found. The fish don’t have color vision, though, which relies on having different cones sensitive to different wavelengths of light.

“Pearlsides found a more economical and efficient way of seeing in these particular light conditions by combining the best characteristics of both cell types into a single cell,” de Busserolles says.
A few other animals have also been found to have photoreceptors that fall somewhere between traditional rods and cones, says Belinda Chang, an evolutionary biologist at the University of Toronto who wasn’t involved in the study. Chang’s lab recently identified similar cells in the eyes of garter snakes. “These are thought to be really cool and unusual receptors,” she says.

Together, finds like these begin to challenge the idea that rods and cones are two separate visual systems, de Busserolles says. “We usually classify photoreceptors into rods or cones only,” she says. “Our results clearly show that the reality is more complex than that.”

Ancient European farmers and foragers hooked up big time

Thousands of years ago, hunter-gatherers native to Europe and incoming farmers from what’s now Turkey got up close and personal for a surprisingly long time, researchers say. This mixing reshaped the continent’s genetic profile differently from one region to another.

Ancient DNA from foragers and farmers in eastern, central and western Europe indicates that they increasingly mated with each other from around 8,000 to nearly 4,000 years ago, a team led by geneticist Mark Lipson of Harvard Medical School in Boston reports online November 8 in Nature. That time range covers much of Europe’s Neolithic period, which was characterized by the spread of farming, animal domestication and polished stone tools.
The new findings lend support to the idea that Europe and western Asia witnessed substantial human population growth and migrations during the Neolithic, says archaeologist Peter Bellwood of Australian National University in Canberra. So much mating occurred over such a long time that “geneticists can no longer assume that living people across Europe are a precise reflection of European genetic history,” he says.
Previous studies of ancient DNA indicated that farmers in Anatolia (modern Turkey) migrated into Europe roughly 8,000 years ago. Researchers generally assumed that newcomers and native hunter-gatherers interbred at first, perhaps as a single wave of farmers moved through Europe to the Atlantic coast, Lipson says. From this perspective, foragers either joined farming cultures or abandoned their home territories and scattered elsewhere. But it now appears that, after a major migration of farmers into Europe, many groups of farmers and hunter-gatherers living in particular regions mingled to varying extents for many centuries, the researchers say.
“Even though there weren’t any major new migrations into Europe after the arrival of farmers, there were ongoing ancestry changes throughout the Neolithic due to interactions between farmers and hunter-gatherers,” Lipson says. Central and northern Europeans next experienced large DNA changes at the start of the Bronze Age around 5,000 years ago, with the arrival of nomadic herders from western Asia (SN: 7/11/15, p. 11).

Lipson’s team analyzed DNA extracted from the skeletons of 154 farmers from Hungary, Germany and Spain, dating to around 8,000 to 4,200 years ago. The farmers’ DNA was compared with DNA from three Neolithic hunter-gatherers found in Hungary, Luxembourg and Spain; a fourth hunter-gatherer from Italy dating to about 14,000 years ago; and 25 Anatolian farmers from as early as 8,500 years ago.

Farmers in each European region displayed increasing amounts of hunter-gatherer ancestry over time, with highs of about 10 percent in Hungary and 20 percent in Germany by around 5,000 years ago, and about 30 percent in Spain by 4,200 years ago. Three farmers from a 6,000-year-old site in Germany fell outside the general trend for that part of Neolithic Europe, displaying 40 to 50 percent hunter-gatherer ancestry.

Genes got passed from farmers to hunter-gatherers as well, although skeletal remains of Neolithic hunter-gatherers are much scarcer than those of their cultivating contemporaries. A hunter-gatherer from the 6,000-year-old German site, identified via chemical markers of diet in the bones, carried around 27 percent ancestry from farmers. A hunter-gatherer discovered at a Hungarian farming site dating to roughly 7,700 years ago possessed about 20 percent ancestry from farmers. Still, previous work has shown neighboring European farmers and hunter-gatherers sometimes kept their distance (SN: 11/16/13, p. 13).

Despite this unexpected evidence of long-term mating among communities with different cultures and styles, the tempo of genetic change and the population sizes of farmers and hunter-gatherers remain poorly understood, says archaeologist Alasdair Whittle of Cardiff University in Wales.

Parents may one day be morally obligated to edit their baby’s genes

A doctor explains to a young couple that he has screened the pair’s in vitro fertilized embryos and selected those that had no major inheritable diseases. The couple had specified they want a son with hazel eyes, dark hair and fair skin. Then the doctor announces that he has also taken the liberty of eliminating the “burden” of genetic propensities for baldness, nearsightedness, alcoholism, obesity and domestic violence.

The prospective mother replies that they didn’t want those revisions. “I mean diseases, yes, but …” Her husband jumps in to say, “We were just wondering if it’s good to leave a few things to chance.”
But the doctor reminds the would-be parents why they came to him in the first place. They want to give their child “the best possible start.”

That’s a scene from the movie Gattaca, which premiered 20 years ago in October. But thanks to recent advances in gene-editing tools such as CRISPR/Cas9, genetic manipulation of human embryos is becoming reality.

Soon, designer babies like those described in the film may even become morally mandatory, some ethicists say.

Gattaca’s narrator tells us that such genetic manipulation of in vitro fertilized embryos has become “the natural way of giving birth” in the near future portrayed in the film. It has also created an underclass of people whose parents didn’t buy those genetic advantages for their children.
Until recently, that sort of fiddling with human DNA was only science fiction and allegory, a warning against a new kind of eugenics that could pit the genetic haves and have-nots against each other. At a symposium sponsored by the Hastings Center on October 26 before the World Conference of Science Journalists in San Francisco, ethicists and journalists explored the flip side of that discussion: whether parents have a moral obligation to make “better” babies through genetic engineering. Technology that can precisely change a baby’s genes is quickly becoming reality. This year, scientists reported using CRISPR/Cas9 in viable human embryos to fix mutations that cause heart and blood disorders. CRISPR/Cas9 acts as a molecular scissors that relatively easily and precisely manipulates DNA. Scientists have honed and developed the tool in the roughly five years it has been around, creating myriad “CRISPR” mice, fish, pigs, cows, plants and other creatures. Its use in human embryos has been hotly debated. Should we or shouldn’t we?

For many people, the fear of a class of genetically enhanced people is reason enough not to tinker with the DNA of the human germline — eggs, sperm, embryos and the cells that give rise to eggs and sperm. By all means, correct diseases, these folks say, but don’t add extras or meddle with characteristics that don’t have anything to do with health. A panel of ethicists convened by the U.S. National Academies of Medicine and Science also staked out that position in February, ruling that human germline engineering might someday be permissible for correcting diseases, but only if there are no alternatives and not for enhancements.

But the question “should we?” may not matter much longer, predicted the Hastings Center’s Josephine Johnston at the symposium. As science advances and people become more comfortable with gene editing, laws prohibiting tinkering with embryos will fall, she said, and it will be up to prospective moms and dads to decide for themselves. “Will editing a baby’s genes be mandatory, the kind of thing you’re supposed to do?”

For Julian Savulescu, an ethicist at the University of Oxford, the answer is yes. Parents are morally obligated to take steps to keep their children healthy, he says. That includes vaccinating them and giving them medicine when they’re ill. Genetic technologies are no different, he argues. If these techniques could make children resistant to infections, cancer or diabetes, then parents have an obligation to use them, he says.

For now, he cautions, CRISPR’s safety and efficacy haven’t been established, so parents shouldn’t subject their children to the risks. He also points out that this sort of editing would also require in vitro fertilization, which is prohibitively costly for many people. (And couples could pretty much forget about having the perfect baby through sexual intercourse. Designer darlings would have to be created in the lab.)

But someday, possibly soon, gene editing could become a viable medical intervention. “If CRISPR were safe and not excessively costly, we have a moral obligation to use it to prevent and treat disease,” Savulescu says.

Using gene editing to cure genetic diseases is something retired bioethicist Ronald Green of Dartmouth College can get behind. “I fully support the reproductive use of gene-editing technology for the prevention and elimination of serious genetic diseases,” Green said at the symposium. “If we could use gene editing to remove the sequences in an embryo that cause sickle cell disease or cystic fibrosis, I would say not only that we may do so, but in the case of such severe diseases, we have a moral obligation to do so.”

But that’s where a parent’s obligation stops, Green said. Parents and medical professionals aren’t required to enhance health “to make people who are better than well,” he said.

Savulescu, however, would extend the obligation to other nondisease conditions that could prevent a kid from having a full set of opportunities in life. For instance, children with poor impulse control may have difficulty succeeding in school and life. The drug Ritalin is sometimes prescribed to such kids. “If CRISPR could do what Ritalin does and improve impulse control and give a child a greater range of opportunities,” he says, “then I’d have to say we have the same moral obligation to use CRISPR as we do to provide education, to provide an adequate diet or to provide Ritalin.”

Green rejected the idea that parents should, or even could, secure a better life for their kids through genetic manipulation. Scientists haven’t identified all the genes that contribute to good lives — and there are plenty of factors beyond genetics that go into making someone happy and successful. Already, Green said, “the healthy natural human genome has enough variety in it to let any child successfully navigate the world and fulfill his or her own vision of happiness.” (A version of his remarks was posted on the Hastings Center’s Bioethics Forum.)

Many traits that would help a person make more money or have an easier life are associated with social prejudices and discrimination, says Marcy Darnovsky, the executive director of the Center for Genetics and Society in Berkeley, Calif. People who are taller and fair-skinned tend to make more money. If parents were to engineer their children to have such traits, “I think we would be inscribing those kinds of social prejudices in biology,” she says. “We get to very troubled waters very quickly as a society once we start down that road.”

Creating a class of “genobility,” as Green calls genetically enhanced people, would increase already staggering levels of inequality, Darnovsky says. That, says Savulescu, “is the Gattaca objection I often get.”

Yes, he acknowledges, “it could create even greater inequalities, there’s no doubt about that.” Whenever money is involved, people who have more of it can afford better treatments, diets and healthier lifestyles — and disparities will exist. “However, this is not inevitable,” Savulescu says. Countries with national health care systems could provide such services for free. Such measures could even correct natural inequalities, he argues.

Johnston worries that genetic manipulation could change family dynamics. Parents might be disappointed if their designer baby doesn’t turn out as desired. That’s a variation of the old problem of unfulfilled parental expectations, Savulescu says. “It’s a problem that deserves attention, but it’s not a problem that deserves banning CRISPR,” he says.