Where does the notion of “freedom of speech” come from? Our Constitution’s first amendment. But cultural anthropologists point back 2 million years ago to Homo erectus and the emergence of cooperative behaviors in hunting-gathering, shared campfires, and communal tool-making.

From the start, there must have been a bias in proto-language toward truth-telling. Survival of a group depended upon accurate knowledge of where food could be found and predators hiding. Mutual trust holds a group together, provides an evolutionary advantage. And as St. Augustine was to write, “When regard for truth is broken down or even slightly weakened, all things will remain doubtful.”

But here’s the rub: When it comes to free speech there is no app in the human brain that fact-checks for truthfulness. All sound bites are initially processed similarly. Additionally, free speech can be weighted by who says it, the authoritative position of the speaker, the emotional tone of the moment, attitudes of friends or the reaction of a crowd — attributes that have nothing to do with truthfulness. So how are we to proceed?

Cicero said, “Before all other things, man is distinguished by his pursuit and investigation of truth.” But this takes time, as it often involves rational analysis, studying alternatives, and discussion with others. By contrast, some people trust their “gut instinct” to any new idea or proposal. Much faster than thoughtful reasoning, it simply feels right. Homo erectus may have debated where to look for food, but not whether to run from a charging lion.

But it is more complicated than that. Not everyone honors truth-telling. Indeed, lying can provide advantage. The first time the shepherd boy cried “wolf,” the villagers grabbed their pitchforks and ran to save the herd. But there was no wolf. The second time they also ran, and the boy snuck into the village and stole from their homes. Unfortunately, lying is part of freedom of speech, and liars can reap advantage in treasure and power. My father often told me this parable of the boy who cried “wolf.” When he cried out a third time the villagers had learned not to respond. But the wolf was there this time and ate the shepherd boy.

“The wheels of justice grind slow,” my mother would say. “But they grind exceedingly fine.”

What can we do to protect ourselves from lies? Should we install fact-checking apps to scrub social media? Should we forbid chronic liars from speaking, publishing and crying wolf? When I try to answer these questions, I hear another question — who decides what is a lie?

In 1644, the English poet John Milton argued against the law of licensing where no one could publish unless they were licensed by the government.

“Give me the liberty to know, to utter, and to argue freely according to conscience, above all liberties... Let Truth and Falsehood grapple; who ever knew Truth put to the worse in a free and open encounter?”

—John Milton, Areopagitica