Not many professors sign copies of their new book about evolution at Denver’s Tattered Cover Book Store before heading out to the Fillmore Auditorium on a Friday night to front a band that is a punk-rock legend.

But Greg Graffin is lead singer and songwriter for Bad Religion and a lecturer in life science and paleontology at UCLA. He has a doctorate in zoology from Cornell University.

Not surprisingly then, Graffin’s new book, “Anarchy Evolution: Faith, Science and Bad Religion in a World Without God,” is, as the publisher puts it, “part rock memoir and part scientific manifesto.”

The book, co-written by Steve Olson, is also about Graffin’s dislike of authority, dogma and fundamentalism, religious or otherwise.

“Religion is an easy target,” Graffin said during an interview with The Post squeezed in between his flight here, the 6 p.m. book signing and 10 p.m. concert appearance.

The band uses religion and religious symbols as metaphors for what’s wrong with society, Graffin said. The band’s logo is a cross with a red slash through it, known as “the cross-buster.”

“There are aspects of religion that we chose to question and confront,” he said.

A craving for evidence

At the same time, the 46-year-old husband and father said, the band has a tremendous following of religious people. His family is full of religious people. And, he said, sounding more like the nice kid who grew up in Wisconsin than the L.A. punk rocker he became at age 15, he likes his family.

“We’ve never gone on stage and bad-mouthed any religion,” Graffin said. “It’s always rubbed me wrong when other punk bands did, when they tell people what to think. That rubbed me just as wrong as Christian rock bands that said you had to get right with God.”

Graffin, as the book title indicates, doesn’t believe in God. Yet he doesn’t call himself an atheist, and he is unimpressed, he said, by a social movement that defines itself by what it doesn’t believe in.

“I don’t bill myself as an atheist but as a naturalist,” he said. “Naturalism is a belief system. A lot of scientists bristle at that. We all have to believe we can find the truth. Evidence is my guide. I rely on observation, experimentation and verification.”

He studies natural forces and evolutionary processes to make sense of his place in the world. He is, he would tell you, a biological accident like the rest of us — the product of random chance as much as natural selection.

“I want some fact-based evidence about where we came from,” Graffin said. “Things we consider mysterious need not be attributed to a deity.”

Graffin said something in the human brain gives us a sense of satisfaction when we feel part of something else, something bigger than ourselves.

“That’s a perfectly good explanation of spirituality,” he said. “I don’t get wrapped up in the good and evil thing so much.”

For him, that something bigger than himself is the parade of life through the eons — evolutionary history.

“A fossil is so powerful. It’s moving,” Graffin said. “This is my ancestor. The naturalist is moved by the fossil . . . not the cross.”

Works, not faith

Graffin said that so much about religion is self-serving. People are promised their salvation and eternal bliss.

To him, a meaningful afterlife is possible — not through one’s continued consciousness — but by living on through your works and in the people you touched.

“Whether you reach a lot of people or have a profound impact on a few people, their memories of you are your afterlife,” he said.

“How can we help people? That’s where the focus should be. What can I do to ensure that what is good now for my family will still be good when I’m gone?”

Electa Draper: 303-954-1276 or edraper@denverpost.com

Read our Bad Religion review