Why Charles Darwin’s great-great-grandson stopped believing in God.

Moderate believers find excuses for Leviticus 20:13, but they can’t argue that the verse is “metaphorical” or “poetic.” It’s situated between specific and practical rules about how to kill and eat animals and when it’s appropriate to beat or stone your wife to death.

Reading the Bible shocked me out of Christianity. I often wonder how many avowed Christians have actually read it, because it is one of the most brutal, repetitive, and contradictory books in existence.

When I came to America in the ‘80s, I began hearing about creationist attacks on the teaching of evolution in schools. For the first time, being a Darwin descendent became relevant. In England and most of Europe, creationism—the idea that the Bible explains the development of life on Earth better than science—was taken about as seriously as alchemy. I watched the antics of creationists out of the corner of my eye, thinking this must be a minor aberrational phenomenon not worthy of attention. But eventually, the subject drew me in. My first book, Trials of the Monkey—An Accidental Memoir, was an account of the so-called Scopes Monkey Trial in 1925 and my trip to Dayton, Tenn., the small town where it took place.

A few years later, Harper’s Magazine asked me to cover the 2005 Kitzmiller v. Dover trial in Harrisburg, Pa. Eleven parents had sued their school district after fundamentalist Christians on the school board tried to get creationism (they later changed the word to intelligent design) taught alongside evolution in the ninth-grade science class. The plaintiffs argued this contravened the Establishment Clause of the First Amendment, the section that prohibits the teaching or presentation of religious ideas in public school science classes. (I later wrote a book about the trial called, for reasons you will understand only if you read it, 40 Days and 40 Nights—Darwin, Intelligent Design, OxyContin, and Other Oddities On Trial in Pennsylvania.)

During the six weeks of the Kitzmiller v. Dover trial, I met many of the leading intelligent design activists. Often described by its critics as “creationism in a lab coat,” intelligent design is almost demented in its denial of what is scientifically demonstrable. Its advocates spin elaborate “scientific” fantasies in defense of religious belief. By the end of the trial—a scientific and philosophical battle in a federal court—one of intelligent design’s most outspoken critics was Republican Judge John Jones. He ruled in favor of the plaintiffs, slamming the fundamentalists and their scientific supporters for their intellectual dishonesty.

After a fellow reporter at a Harrisburg newspaper revealed that I was a Darwin descendent, I became an object of curiosity and sometimes animosity. I was invited to homes and churches in the area to talk about my views, and on a couple of occasions to endure attempts at conversion. A preacher told me that Darwin was synonymous with Satan and that I was therefore damned myself. This was unusually extreme, but I often met people who, given a choice between evidence and faith, instantly chose faith no matter how good the contradictory evidence was. These conversations had a unique quality: I was talking to people whose way of thinking—or not thinking—had usually been ingrained in them as children. No amount of rational discourse would change their minds. They were hardwired to have blind faith and be suspicious of reason. Faith had made them stupid, angry, and, I would argue, dangerous.

Faith is why we don’t want Iran to get a nuclear bomb. It’s also why we are terrified of Islamic radicals taking over Pakistan, where nuclear weapons already exist. Faced with the potentially horrific consequences of ancient faith married to modern weaponry, we should be questioning the whole concept of religious faith, including our own. But, for obvious reasons, we aren’t. As I learned in Pennsylvania, that faith—a diseased appendix of the mind—is not so easily removed.

When I read the Bible as a child, my disenchantment with religion began. But ironically, it was in the state founded by William Penn to be a liberal and inclusive religious sanctuary that I saw so much angry and exclusionary faith. It was there that I discovered its universal potential for harm. I left Pennsylvania with my journey to atheism complete.