For decades, the idea of standing properly upright carried considerable political and social baggage. Slouching was considered a sign of decay.

In the early 20th century, posture exams became mainstays in the military, the workplace and schools, thanks in part to the American Posture League, a group of physicians, educators and health officials that formed in 1914. In 1917, a study found that roughly 80 percent of Harvard’s freshman class had poor posture. Industrialists piled on with posture-enhancing chairs, products and gadgets.

But the actual science doesn’t support the conventional wisdom about proper posture, Beth Linker argues in her new book, “Slouch: Posture Panic in Modern America.” Dr. Linker, a historian and sociologist of science at the University of Pennsylvania, recently sat for an interview with The New York Times; the conversation has been condensed and edited for clarity.

Nice to meet you.

Your posture looks pretty good. And it doesn’t matter — that’s the whole point of my book. It’s fake news.

Our obsession with great posture is fake news? I’m off the hook!

Concern for posture, as a matter of etiquette, has been around since the Enlightenment, if not earlier, but poor posture did not become a scientific and medical obsession until after the publication of Darwin’s “On the Origin of Species” in 1859. He posited that humans evolved through natural selection, and that the first thing to develop was bipedalism; in other words, standing upright preceded brain development.

This idea was controversial because convention taught that higher intellect distinguished humans from nonhuman animals, and now it appeared that only a mere physical difference, located in the spine and feet, separated humankind from the apes.

In other words, bad posture was primitive.

Actually, quite the opposite. Bad posture was assumed to primarily affect “civilized” individuals — people who no longer engaged in physical labor but instead enjoyed the fruits of mechanized transportation, industrialization and leisure.

With the rise of eugenics in the early 20th century, certain scientists began to worry that slouching among “civilized” peoples could lead to degeneration, a backward slide in human progress. Posture correction became part of “race betterment” projects, especially for white Anglo-Saxon men but also for middle-class women and Black people who were trying to gain political rights and equity. Poor posture became stigmatized and defined as a disability. As I show in my book, people with postural “defects” were regularly discriminated against in the American workplace, educational settings and immigration offices. People with disabilities had no legal protection at the time.

Also, this was an era when physicians and public health officials began to focus more on disease prevention to control the spread of infectious contagions like tuberculosis. Good posture was understood to be an effective way to stave off deadly diseases, leading to campaigns that taught Americans how to stand up straight.

When tuberculosis rates declined in the 1940s — partly as a result of the discovery of antibiotics — scientists and physicians began to draw a causal link between poor posture and back pain. President John F. Kennedy, who had chronic back pain and his own posture guru, reinvigorated the President’s Council on Physical Fitness in order to promote uprightness and strength among the nation’s citizens.

For much of the 20th century, posture awareness campaigns were seen as an inexpensive way to improve national health, especially compared to costlier health investments such as improvements in housing, infrastructure and nationalized health insurance coverage. Posture crusaders also tended to hold individuals accountable for their own failing health, rather than looking to structural problems. For example, they would blame a back pain sufferer for having caused the problem, for failing to sit and stand properly, for being a slouch.

And you contend that was unfair.

There was really no proof of causality, then or now.

But the belief gained traction because it legitimized age-old assumptions about the importance of upright posture to human ability. Posture assessments became a quick and efficient way to size up another person’s character, intelligence and health — all in one fairly simple exam.

I’m not a posture denier. I think posture therapy can be a powerful tool when used to alleviate existing back pain. I myself frequent a physical therapist for my own back pain, and I use standing desks, ergonomic chairs and yoga to contribute to my sense of well-being. But these devices and remedies offer much more than a fixed notion of good posture.

What I question is how much posture correction can do for a healthy, pain-free person in terms of preventing future ills and the inevitability of aging. The posture panic created over 100 years ago, and the simplistic message behind it, was good for self-discipline and for business. In a certain respect, manufacturers of ergonomic chairs, back braces, bras and shoes, even today, want to keep the panic alive.

Do we even have a good definition of what is good or bad posture? We don’t. No one can agree on what the standards are. Also, the human body is incredibly dynamic, and each of our anatomies are, to some extent, distinct. To say that there’s, like, some kind of static norm is not in keeping with the reality.

It’s not just standing as erect as possible with your chin tucked back?

Plumb-line verticality is what it’s called; that’s one way to assess posture. You have certain anatomical markers in line with each other. But we’re never static. How long can you really hold a posture that is “good”?

Until we get off this Zoom call and I can relax.

The scientific study of the effectiveness of posture correction has been hindered by a scandal that was covered by The New York Times Magazine in the 1990s. The article reported that for several decades until the 1970s, Ivy League schools took nude pictures of undergraduates to check their posture, and that these pictures still existed in the Smithsonian Archives. My own research has shown that posture photography happened not just at elite universities but at colleges, hospitals and prisons across the country. The practice of taking nude posture pictures largely came to an end in the early 1970s because of concerns about propriety and personal privacy.

After the Times exposé, entire archival holdings containing a century’s worth of posture science data were burned or shredded.

The scandal did not question the presumed benefits of posture correction; rather, it took issue with the conventions of measuring posture. So the health belief that posture is an indicator of future health — that it can be a predictor of back pain and neck pain — remained in place. Not until recently have certain studies shown that you can adopt all kinds of posture, even the occasional slouching, and be just fine.

In sum, you argue that there’s no connection between a person’s posture and morality, and that there may be no connection to long-term health.

In some ways, it’s the phrenology of the 20th century. We use posture to judge character, intelligence and physical ability. Like, if you’re a slouch, that also means that you’re somehow lazy.

It’s shallow and ableist to estimate what another person can or cannot do based on their posture. In terms of long-term health, I think the jury is still out on that.