One summer morning almost 30 years ago, my uncle Grainger Hunt phoned to say that a young bald eagle he had been watching on the Salt River in Arizona had begun its adolescent migration. The bird had been fitted with a small radio beacon that beeped every second or so, and my uncle owned a Cessna 182 with radio receivers mounted on each wing to track the bird. So I caught a jet to Phoenix and climbed aboard the Cessna, hoping that the young eagle would lead us to some unknown fly-fishing spot, and I would sell the adventure story to Sports Illustrated.

The trip felt elemental: learning from my uncle how to track an animal—even if our quarry wore a radio tag, we were in an airplane, and our goal was to learn more about the national bird to keep it safe. As we flew, we talked about birds of prey and predators in general. Grainger was a hunter, a forager of wild food, and he earned his doctorate in evolutionary biology. He pointed out that we are predators: our eyes are in front, our front teeth are sharp, and our hands and arms evolved to throw a rock or a spear or a 100-mile-per-hour fastball. We coexisted with wolves and transformed them into hunting companions and pets. We corralled prey species like horses and taught them to carry us into battle. And we killed and ate pretty much everything else—including each other.

My uncle argued that weapons supercharged human evolution and led to our expansive consciousness. Once it became apparent that anyone could pick up a rock and smash the skull of the sleeping alpha male, “survival of the fittest” had to adapt—fast—meaning that people had to become both clever and wise. Teaching kids not to kill each other suddenly became as important as teaching them how to hunt. Thus, casting that first stone may have sown the seed for the human taboo against cannibalism, as well as codes of honor, rights of passage, high-stress politics, and even religions. The plot of the ancient play Oedipus Rex captures the essence of a basic principle: if you kill your dad and sleep with your mom, she will hang herself and you will poke out your own eyes with a stick. Don’t go there! The story of Abraham and Isaac makes a related point: Hey, Dad, you don’t really have to sacrifice your son—God will be happy with a goat. Then Jesus declared that a sacrifice of bread and wine was just as good—but he had to get himself killed to make the idea stick. That’s a predator’s price for progress!

Such ideas were fun to talk with my uncle about, and chasing an eagle over Pueblo Indian country made the conversation especially poignant. The previous year, hundreds of people had gathered at the ruins of the ancient Anasazi pueblo in Chaco Canyon for an astral alignment called the Harmonic Convergence. These well-intentioned souls believed the Anasazi had a special energy to bring peace into the world, and some argued the Anasazi were an advanced civilization that transported to another planet. Alas, the archaeological evidence suggests the Anasazi were taboo-breakers who ate one another as a means of social control. The evidence of cannibal terrorism—from stirred and cooked human bones to the remains of human poop containing DNA of other humans—is unpalatable but irrefutable. The Anasazi were eventually destroyed by the Toltecs, followed by European invaders who wiped out nearly all the Native Americans, then Hitler studied our reservation system to craft his “ultimate solution” for the Jews, who are lurching toward apartheid for the Palestinians. We humans do make progress, but peace is hard for predators.

Discovering such truths is difficult. Accepting them is harder. And yet we are remarkably good at solving problems—especially when doing so is connected to one’s immediate health and happiness. Let me explain.

Before he became a biologist, my uncle was a falconer, and the birds of prey he loved were rapidly going extinct, their eggs mysteriously breaking under their own weight. So Grainger went to see a presentation by Derek Ratcliffe, the world’s foremost authority on peregrine falcons, and Ratcliffe showed a graph that established the link between the declining peregrine population and the expanding use of the pesticide DDT. Armed with that truth, falconers battled DDT, bred the endangered birds in captivity, and released them into the wild. That hard work is why I can look out my office window and the bald eagle flying by seems like no big deal. Progress!

Now we have other scary graphs to worry about. Rising CO2 is obviously one. So is rising financial inequality. But the chance of solving these problems has been temporarily trumped. One graph that really scares me right now—that we can fix—shows the increasing use of glyphosate (Monsanto’s Roundup) and the rapid rise in celiac disease. Oh my God! The problem isn’t that America suddenly became allergic to gluten or wheat. The problem is that we’ve weaponized our food against bugs—and it’s killing the bugs inside us that digest the gluten. Much like DDT and thinning eggshells, glyphosate is likely thinning our gut bacteria—which manifests as skin rashes, lactose intolerance, joint pain, bone loss, fatigue, and depression.

And here’s the punch line; the French don’t allow such weaponized crops, and the New York Times reported that France has higher crop yields than we do. We’re poisoning ourselves for no reason. We can eat better and feel better, that’s for sure.

That grand adventure with the eagle ended at Yellowstone Park, which is where Grainger had taught me to fly-fish when I was a teenager. So I decided there weren’t any places left that only eagles knew about, and it seemed sad. But the larger truth is that we’re getting to know our planet really well. We know enough to heal ourselves as well as the earth—if we can just stop biting one another long enough to do it.