Michael Caronna / Reuters

Here’s what I remember from biology class at my public high school in Texas: We learned everything there is to know about the Krebs cycle. We collected bugs in the heat and suffocated them in jars of nail-polish remover. We did not, to my recollection, learn much of anything about how the human species originated.

Most scientists believe that the beings that would become humans branched off from the common ancestor we share with chimpanzees, our closest living relatives, about 6 million years ago. We did not learn this part—the monkey part. That is, our shared ancestry with other primates. Because this was nearly 20 years ago, and memories tend to fade with time, I checked with several friends who went to the same high school at the same time. None of them recalled learning anything about human evolution, either.

The only high-school biology class I took was in ninth grade, and it was apparently so uninteresting to me that I don’t remember my teacher’s name. (My former school district did not return a request for comment.) My teachers were for the most part religious, though they appeared to stay firmly within the bounds of the state-mandated curriculum. In another class, my teacher showed us diagrams of the human eye, then snuck in a remark that the complexity of the eye is convincing evidence that there is a Creator.

I didn’t have many other opportunities to learn about humanity’s origin. The pastors at the evangelical youth group I attended—outside of school—told me it’s possible that dinosaurs and humans walked the Earth at the same time. We can’t know for sure, they said, because carbon dating is not to be trusted.

My experience was far from unusual. While only 13 percent of teachers said they advocate creationism or intelligent design in the classroom, based on a survey of 926 public-high-school biology teachers done in 2007, the most recent data available, the majority do not explicitly advocate either creationism or evolutionary biology. This “cautious 60 percent,” write the Penn State political scientists Michael Berkman and Eric Plutzer in their 2011 article on the topic, “are neither strong advocates for evolutionary biology nor explicit endorsers of nonscientific alternatives.” (Plutzer is in the process of conducting a new survey now; he told me preliminary data suggest little has changed since 2007). And there are recent examples of school administrators doubting the value of teaching evolution. In Arizona last year, three of the candidates vying for state school superintendent wanted students to be taught intelligent design, the Arizona Daily Sun reported. In 2017, a Utah school-board member nicely summed up the concept of “teaching the controversy” when she suggested “maybe just teaching theory and letting both sides of the argument come out—whether it’s intelligent design or the Darwin origin.” Except that people who study evolution also tend to believe there is no scientific controversy.

Some educators in this ambivalent 60 percent tend to teach evolution only as it applies to molecular biology, Plutzer said, but not the macroevolution of species. (This seems like what happened to me.) Others distance themselves from the material even as they tell students it will be on a standardized test. “Their primary concern is not offending the students or their parents by characterizing the science in a way that seems to be challenging religious faith,” Plutzer told me. “I think that in some cases, the teachers themselves have doubts.”

Additionally, some teachers expose students to different “theories” about evolution and encourage them to make up their own minds. “But does a 15-year-old student really have enough information to reject thousands of peer reviewed scientific papers?” Berkman and Plutzer write in their article.

Some of these teachers might even introduce evolutionary ideas such as natural selection and microevolution. But they skip the part we skipped—the monkey part. The reason is perhaps unsurprising: Creationists “are not invested in whether evolution affects the sizes and shapes of the beaks of finches in the Galápagos,” says Glenn Branch, the deputy director of the National Center for Science Education, which supports teaching evolution in schools. “They are worried about whether people were created in the image of God himself.”

The reason public-classroom instruction varies so much, Branch says, is that teachers have many opportunities to personalize what they teach to students. State standards differ, and local school boards develop curricula that are designed to meet those differing standards. Teachers take those curricula and develop lesson plans. Then they go off into their classrooms. Do they teach exactly what’s in the lesson plan or tweak it? It’s hard to know for sure.

If teachers are aligned with the values of the community, parents might not complain about what students are learning, Branch says. If parents do complain—because, say, they believe that the teacher has improperly brought up religion in the classroom—the principal might force the teacher to change his or her ways. If the principal backs up the teacher, it might become fodder for a lawsuit.

The courts have so far been on the side of the secular. Creationism has lost every major U.S. federal court case in the past 40 years, Berkman and Plutzer write. And not even the best-known opponents of evolution overtly come out against it. Take the Discovery Institute, which describes itself as an “educational and research organization” with “more than 40 affiliated scientists and scholars, many of whom think key features of life and the universe reflect evidence of intelligent design rather than an unguided process.” Its vice president, John West, told me via email that the best approach to teaching human evolution in public high schools is to “give students an accurate understanding of the current science, which includes exploring unresolved issues and areas where scientists continue to disagree.” These include, he said, “debates about how humans’ unique capacities for language, math, ethics, fire-making, and art developed in the history of life.” Sarah Chaffee, the institute’s program officer for education and public policy, told me, “The Next Generation Science Standards inform most states’ science standards. These standards mention many aspects of evolution, but they do not specifically reference human evolution.” If teachers aren’t teaching human evolution, she said, “it is very likely the main reason is solely the fact that it is not in the science standards.” (Branch says while it’s true that human evolution is not in the NGSS, other factors also might explain why teachers don’t present it.)

How does this variation in evolution education affect students? Plutzer suggested that “teaching the controversy” opens the door to the idea that matters of science are up to students to decide for themselves. “The broader consequence is that students will come away with the idea that important elements of science are based in values and not evidence, and that gives them license to reject other kinds of science,” he said.

Branch says lacking a knowledge of human evolution might make it harder for, say, doctors to understand superbugs, or for farmers to understand the nuances of agriculture. I’m a little skeptical of that argument. There are great doctors in Texas, and certainly plenty of great farmers too. The internet wasn’t as ubiquitous when I was in high school, but it was still possible to read and explore on one’s own. Today, that’s even easier.

Instead, the real problem with not learning about human evolution in high school might be the simple frustration of not knowing what other people know, when they know it. Public school is supposed to provide Americans with an even foundation on which to build our reality. Among other things, its purpose is to show us how we got to where we are today. For many students, the origins of that story remain opaque.

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