Nothing Is “Normal”? Expect Variation

Why we keep rethinking human variation, representation, and the language of A&P

What does a normal human body look like?

Uh-oh.

That question gets complicated pretty quickly. Is “normal” what is most common? What is average? What falls within some expected range? What is healthy? What looks like the illustration in an anatomy textbook?

Those aren't necessarily the same thing. And that matters when we're telling students the story of the human body.

Variation isn't an exception to the story

Back in 2021, I wrote about our long-running effort toward Diverse Representation in Anatomy & Physiology.

That work goes back several editions, but it kicked into much higher gear during the revision of the 10th and 11th editions. We looked hard at who appeared in our photos and illustrations, whose bodies were represented in our examples, and how our language described the varied humans our students will eventually encounter in healthcare, fitness, wellness, and other professions.

Then we kept going in the 12th edition. Because variation isn't an exception to human anatomy and physiology. Variation is human anatomy and physiology.

I've been thinking aloud about this for years. In The A&P Professor (TAPP) Episode 43, Anatomic Variations in Humans, I wondered whether “normal” anatomy is partly a useful—or maybe even mythical—construct. We need some representative model when we begin teaching anatomy. But no actual human being perfectly matches every feature of that model. The A&P Professor

Age and development change us. Genes vary. Embryological events vary. Hormones vary. Nutrition, activity, environment, injury, disease, and lived experience all contribute to what our bodies look like and how they function. Even genetically identical twins develop differences.

So perhaps the real story of human anatomy is not uniformity.

It's unity with variation.

Then there's that word: “normal”

During the 11th-edition revision, the Patton Team did something rather tedious.

We reconsidered every instance of the words normal and abnormal.

I later shared that project during the 2023 HAPS Annual Conference workshop Editing A&P Textbooks Through a DEI Lens: Authors' Perspectives.

Why fuss over two perfectly ordinary words? Because when we stopped and asked what we meant by normal, we often discovered that we meant something more precise: typical, average, expected, within a reference range, or perhaps simply healthy.

Those aren't synonyms.

Research examining the concept of normality in medicine makes essentially the same point. Normal can refer to statistical typicality, health, desirable function, an ideal, or other concepts depending on context. Mixing those meanings can create confusion.

And abnormal can be even trickier. Being statistically unusual doesn't necessarily mean unhealthy. Being outside an average doesn't necessarily mean pathological.

Yet normal and abnormal carry everyday meanings that can quietly slide from common versus uncommon into good versus bad—or even acceptable versus unacceptable.

Usually, that's not what we're trying to say in an A&P textbook.

So we counted them

Here's what happened when we deliberately reconsidered those terms.

Edition	“Normal”	“Abnormal”	Combined
10th	743	341	1,084
11th	91	68	159
12th	82	54	136

Most of that dramatic shift occurred during the 11th-edition revision. But we didn't declare victory and move on.

The 12th edition gave us another opportunity to make a careful second pass—not only at normal and abnormal, but at many other words, images, examples, and explanations related to human variation.

That graph makes the change rather hard to miss.

And then something interesting happened

Here's a bit of evidence we didn't have when we began this work.

In 2026, researchers published a study specifically examining how anatomical variation is described in anatomy textbooks. They found that abnormal was used more often than more neutral descriptors, including in some contexts involving common or asymptomatic variations. Their recommendation was to teach anatomical variation explicitly and use neutral, prevalence-aware terminology rather than automatically framing variation as defective or pathological.

Well.

That sounds familiar.

I don't mean that as “See? We were right!” Science and teaching are rarely that tidy. But I do find it reassuring that an independent analysis published after much of our revision work identifies essentially the same problem we had already been wrestling with.

This wasn't a search-and-destroy mission

We didn't ban the words normal and abnormal. Sometimes one of them really is the clearest word.

The point was to stop using either one automatically.

If we mean average, say average. If we mean typical, say typical. If we mean disease, say disease. And if we mean outside the expected reference range, perhaps that's what we should say.

A nice example occurs in our homeostasis chapter. For the 12th edition, a figure label changed from setpoint value to setpoint range, and an area previously labeled abnormal became disease. We also added explicit arrows representing physiological fluctuation.

That's more than swapping one fashionable word for another.

It's more accurate physiology.

“Typical” doesn't mean everybody

We use typical fairly often now when we need a representative starting point.

That distinction matters. A textbook has to teach general patterns. We can't introduce every possible variation every time we introduce a structure, so we may begin with the typical structure of something.

But typical isn't meant to imply the only proper version.

In Chapter 1, for example, we clarified the continuum of variation among sex characteristics and added explicit discussion that even twins exhibit anatomical variation. 

That reflects something I discussed in TAPP Episode 43: teaching often has to begin somewhere near the middle of a spectrum. Then we help students discover the variation around that starting point.

The representative model is the beginning of the story—not the boundary of reality.

What students see matters, too

Words were only part of this project. We also continued revising the visual story.

The 12th-edition revision notes describe this as an ongoing effort to replace some classic illustrations with a broader spectrum of variation among human subjects. That helps more students see themselves represented, but it also prepares future health professionals to encounter more of the variation they'll see in real people. 

That effort shows up throughout the book. Muscle figures were revised to show more varied skin colors and additional examples of human variation. Elsewhere, figures were revised for varied skin tone, hair color and style, and even a subject with a leg prosthesis. 

We've updated cases, names, and other details, too. Individually, those changes may seem small. Taken together, they change the population students encounter as they move through the book.

In short, we kept asking not only What do we say? but also What do students see?

Both matter.

Anatomy education still has some catching up to do

There's growing evidence that this is not a trivial concern.

A 2026 analysis of contemporary anatomical education resources found continuing imbalances in sex and skin-tone representation across major anatomy textbooks and digital resources. The study wasn't an analysis of undergraduate A&P survey texts, so I don't want to stretch its findings beyond what it examined. But it reinforces the larger point: the anatomical bodies students repeatedly see help establish their mental picture of what a human body looks like.

And illustrations aren't merely decoration. They're part of the teaching.

If nearly every body a student sees looks essentially the same, that's a lesson.

Maybe not the lesson we intended—but still a lesson.

Why does this matter?

There's an inclusion argument, of course. I've made it before.

Students should be able to see themselves as belonging in the population we're studying and in the health professions they're preparing to enter. That's one reason I discussed reflecting diversity and using inclusive language in TAPP Episode 108, The Inclusive Anatomy & Physiology Course.

But there's also a straightforward A&P argument.

We are supposed to be teaching students about human bodies.

Actual human bodies vary.

Students preparing for health professions need to know that. A healthcare professional who has unconsciously learned that one idealized body represents “normal anatomy” and everything else is a deviation from it has learned an incomplete version of anatomy.

So has an athletic trainer. So has a fitness professional. So has anyone whose work involves understanding real human structure and function.

What does “normal” mean, anyway?

I wrestled with that question directly in TAPP Episode 101, Even MORE Test Answers | Normal Body Temperature?.

Body temperature makes a great example. Even something as familiar as “normal body temperature” varies among people, across the day, with measurement site, under different physiological circumstances, and across populations and historical periods.

A mean can still be useful. A reference range can still be useful. A representative pattern can still be useful.

We don't have to abandon any of those.

We just have to remember what they are: models of reality, not definitions of who counts as a proper human being.

Another pass. And then another.

One thing I've learned from this process is that inclusive and accurate representation isn't a box we can check.

DONE!

Nope.

Language changes. Science changes. Our awareness changes. Sometimes we discover that wording we thought was perfectly clear carries an implication we never intended. Sometimes new research reveals variation we weren't even aware of. And sometimes somebody simply points out something we've been staring at for years without seeing it.

That's why the major push in the 11th edition wasn't the end of this effort. We made another rigorous pass in the 12th edition. The official revision notes explicitly describe bias-aware language and varied representation as continuing, research-informed processes rather than finished projects.

And I'm sure there will be more to fix.

There always is.

Expect variation

A&P works because human bodies share remarkable patterns.

That's the unity part.

But those patterns occur across an equally remarkable range of individual differences.

That's the variation part.

Students need both.

So perhaps the most useful lesson isn't that this structure, measurement, or body is normal.

Maybe it's this:

Here's the pattern. Here's the range.

And expect variation.

If you don't have your own copy to review, please request a free instructor review copy of the new 12th Edition of Anatomy & Physiology.