some historians have argued that the very concept of childhood as we know it did not properly exist in people’s minds until a few centuries ago, a rich body of evidence suggests that parents haven’t changed much at all - that they have always gone as far as possible to protect their offspring, in some cases outfitting them with early versions of the very safety devices we now think of as quintessentially modern.

Over the past 20 years or so, historians specializing in childhood have forged a body of work that has begun to change how we see that past. The experience of childhood has, indeed, changed dramatically over time. And though

At the center of this debate, as the authors of books like “Free Range Kids” and “Too Safe For Their Own Good” will tell you, is a worry that contemporary parenting trends are producing a generation of weaklings, kids so insulated from the world around them that they’ll never learn to navigate risk or handle pain. And though on the surface the debate concerns the future of childhood, it is also built on a belief about the past: that being a kid used to be radically different than it is today - more free, more rough-and-tumble, and on a deep level, better.

As these products proliferate - perhaps you’d like to dress your baby in a full-body jumper with special pockets that make it impossible to drop him? - so does the sentiment that perhaps we’re going too far, and that parents have let their protective instincts get the best of them. In books, magazines, and parenting blogs, a divisive public debate has placed safety-conscious moms and dads on the defensive against a chorus of critics who believe America’s children are being crippled by paranoid overprotection.

The baby helmet is just one piece of the protective armor being built around childhood these days. There are soft pads to shield babies’ knees from irritation while they’re learning how to crawl. Specialty feeding spoons change color when the

Not long ago, babies were only fitted with helmets if they were born with irregularly shaped heads. But in recent years, entrepreneurial manufacturers have expanded the market, creating helmets designed for any children whose parents want to protect them from scrapes and bruises while they’re learning how to stand upright and walk. These helmets have names like ThudGuard, SoftTop, and Baby No Bumps. Some even come with decorative Mickey Mouse ears.

Perhaps you’ve seen the helmet babies - on the T, strapped into portable carrying chairs between fidgety parents; on the street, curled up in slings against the chests of dads. Helmet babies look strange, their soft baby heads encased in shells of foam, tight straps hugging their chins. If you’ve spotted one at close range, you may have felt the temptation to ball your hand into a fist, reach over, and give that fortified little noggin a gentle “knock knock.”

Ariès’s view of childhood as a cultural construct has remained enormously influential among historians. But since it was published, the particulars of his research on the Middle Ages have been largely discredited by specialists. True, families in medieval Europe did not have great car seats. But the idea that they didn’t care about protecting their children from perceived harm - the idea that humans didn’t treat children as special until the dawn of modernity - is contradicted by evidence suggesting that parents in the Middle Ages worried about their kids no less than we worry about ours today. Parents without vaccines or childproof locks relied instead on amulets and rituals to protect their kids. According to Colin Heywood, a historian at the University of Nottingham and author of “A History of Childhood,” some parents would deliberately not wash their babies’ heads because they thought it would protect their souls; mothers would bury their babies’ umbilical cords in the ground for good luck. There were more practical protective measures taken, too, most notably swaddling, which involved wrapping babies in tight bandages so they couldn’t move and sometimes even hanging them on the wall for safety. According to Barbara Hanawalt, a historian at Ohio State University who has studied child-rearing in medieval England, toddlers were often swaddled in cradles so they couldn't crawl into a fireplace or well while their parents were out working in the fields.

“He thought parents just didn’t attend much to kids,” said Michael Zuckerman, a historian at the University of Pennsylvania who has edited a book on childhood. “Adults weren’t judged by the goodness of their child rearing. Nobody thought the worse of you if you ignored your kids or neglected your kids.”

This belief formed the basis of one of the first works of childhood history ever published, when in the year 1960 a French historian named Philippe Ariès made the provocative claim that, during the Middle Ages, children had been treated like miniature adults. Ariès argued in his landmark book, “Centuries of Childhood,” that until the 18th century or so, the concept of childhood as distinct from other life stages did not really exist.

We want to believe there was a time when it was all very different - when kids could be kids, and parents weren’t too risk averse to let their offspring grapple with the world’s harshness. This is the idea embedded in much of the criticism one hears about contemporary child-rearing: that once upon a time kids were taught responsibility instead of fear, and were encouraged to make formative mistakes instead of being vigilantly insulated against them.

What an overload of safety measures might actually do to children, psychologically and emotionally, remains up for debate. And while it’s incontrovertible that children used to have more freedom, it’s also clear that the march towards ever more sophisticated methods of child protection began long ago - as did the worries about their effects. Helmets for babies may seem a little extreme, but there is every reason to think they were also inevitable. The proper response to our zeal for safety may lie not in fighting the impulse, then, but in engineering ways to blunt its negative effects.

Starting in the 1950s, according to historian John Burnham at Ohio State University, after antibiotics and vaccines had decisively nullified the age-old threat of infectious disease - and thus reduced pediatricians’ caseload by an estimated 60 percent - doctors and public health officials started concerning themselves much more with the risk of childhood accidents. After that, dangerous substances like medicines and pesticides started coming with childproof caps, and lawn mowers started to be made with protective shields so that children wouldn’t cut their hands on the blades. From there, it was not such a long walk to special rubber duckies that change color if baby’s bath water gets too hot.

By the mid-19th century, distinctly modern approach to protective parenting began to creep up, especially in the upper middle classes. In 1897, a child-rearing manual by Frances Fisher Wood advised parents to keep children away from stairs and install bars on windows. In a related development, Victorian England saw the emergence of the “pudding hat” for toddlers, basically an early version of the ThudGuard, as well as the use of “leading strings” that prevented kids from straying too far when their parents took them outside. (These strings survive today, as harnesses for young walkers.) Childhood remained rougher in the working classes until late in the 19th century, when child labor laws made it illegal for youngsters to hold factory jobs.

Some historians, including Ariès, have interpreted the laissez-faire mentality that followed from that fatalism as evidence that medieval parents were fundamentally indifferent to their children. Others have opposed that view, arguing that parents just didn’t have the technology or the resources to protect their young from the dangers that threatened them. Regardless, we know the sense of fatalism began to lift in the 18th century. Thanks in part to ideas expressed in Jean-Jacques Rousseaus influential book Emile: or, On Education, published in 1762, parents, at least in the West, started taking on more responsibility for their children and thinking of them as increasingly precious and special creatures. As medicines appeared and mortality rates fell during the 1800s, more and more parents started feeling like they had some control over their childrens health and security.

One looming difference between then and now was that parents had little power to do anything about the far bigger risk that threatened their families, namely disease. Infant mortality rates were astronomical: According to one estimate, a quarter of newborns died before they turned 1. In the context of such grave and unrelenting peril, trying to prevent children from sustaining minor injuries like bruises, bumps, and bloody noses would have struck most parents as being about as urgent as keeping their fingernails clean. Young life was so precarious, in fact - and families so large - that parents were forced to adopt a fatalistic attitude towards the grim inevitability that some of their many children simply would not survive.

At this time, reader, it seems only right to confess that I was a helmet baby. More accurately, I was a helmet third-grader, sentenced to a whole year of life in a thick white shell after falling off my bike in the midst of a major wheelie damaging one of my eardrums. The doctor told my mom that if I bumped my head again in the near future I would run the risk of going completely deaf. A helmet was bought; my teachers were informed. For the rest of third grade, I was not allowed to walk to school, go out for recess, or eat lunch unless I was wearing my armor on my head. Yes, my fellow third-graders called me Helmet Boy. Of course they did.

In the 20 years since, I’ve often wondered how the helmet changed me. Am I weaker for having worn it? Less confident in my ability to withstand the punches life throws at me? They’re the same questions that we as a culture have been asking about overprotective parenting in general - not just recently, it turns out, but throughout history. Even Rousseau, who was so instrumental in spreading the idea that children were creatures in need of care, was concerned that parents could go overboard. He railed against swaddling, for instance, arguing that children should be dressed in loose-fitting garments so they could get a feel for what the world was really like. “Experience shows that children delicately nurtured are more likely to die,” Rousseau wrote. “Accustom them therefore to the hardships they will have to face . . . .Dip them into the waters of the Styx.” According to the book “Perfect Parents,” in which Christina Hardyment recounts the history of baby care advice, some parents of Rousseau’s time went even further: They thought they could help their babies develop stronger constitutions by shooting guns off near their heads.

It sounds barbaric, perhaps, but the idea underlying that extreme gesture - that parents needed to compensate for the relative safety in which their children were growing up - remains a powerful strain of thinking today, and may not be the wrong way to approach things. Even as parents stock up on antibacterial lotion and cover ever corner in their homes with foam, some people - perhaps even the same parents - are looking for ways to give their kids a dose of the independence and risk they’ll need to become healthy and well adjusted later.

Michael Ungar, a social work professor at Dalhousie University in Halifax, Nova Scotia, and author of “Too safe For Their Own Good,” has written about how the overprotective impulses that lead to things like helmets and kneepads during children’s early years end up hurting them as teenagers and adults. Though Ungar says there has never been a clinical study comparing people’s psychosocial health based on their parents’ child-rearing strategies, he says that developmental psychologists have shown that experiences involving independent risk-analysis and problem-solving do contribute to individuals’ maturity and stability. If parents prevent their kids from having those experiences, Ungar argues, those kids will be stunted in various ways. (And some they might not expect: Whatever more subtle effects it had, my third-grade year gave me a strong lifelong aversion to wearing helmets.)

Ungar’s solution, in advising families, has not been to pressure parents into relinquishing their protective strategies. Instead, he asks them to reflect on their own childhoods, and to remember what lessons they learned from the freedoms they were given. Whatever those lessons are, Ungar says - whether they’re related to risk-taking, danger, or pain - parents are encouraged to create situations that might lead to similar breakthroughs for their kids without putting them in harm’s way.

His philosophy - that we can reverse-engineer risk into our kids’ lives without actually risking all that much - can be seen in the work of other parenting experts such as Gever Tulley, author of “Fifty Dangerous Things (You Should Let Your Children Do)” and Tim Gill, author of “No Fear” and a leader in the movement to promote more outdoor playtime. It can also be seen in the development of new playgrounds specially designed to challenge kids and develop their sense of adventure by forcing them outside their comfort zones.

“You want kids climbing trees, you want them having bumps and bruises,” Ungar said. “It’s an equation for parents to do the math on: If you take away all those things - if you take away all the risk - that’s great. But then you have to put back opportunities for the life lessons.”

Leon Neyfakh is the staff writer for Ideas. E-mail lneyfakh@globe.com.

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