Our Bodies, Ourselves, which turns 40 this year, was the sexual manifesto of its era: the first book on sexual health written by women for women that would go on to sell more than 4 million copies. As the women’s health collective behind Our Bodies, Ourselves prepares to release its ninth edition—updated and revised with new chapters on body image, date rape, and plastic surgery—we sifted through three editions of the text to find out what’s changed. Five of the biggest, most comical, and most fascinating revelations:

1. What We Know About Orgasm

Then: with little scientific data to go on, the book’s original authors touted the clitoris (klit'-o-ris) as the only part of the female anatomy where orgasms could occur. By 1992, when the book’s fifth edition came out, we knew it wasn’t so simple: the text acknowledging “new debate” over different types of orgasm, and the parts of the anatomy that helped them happen. Now: the authors note that some women find the cervix and uterus crucial to orgasm—and that it’s a process far more complex than one magic button.

2. The Beauty Myth

High heels and bras may have kept early-1970s women enslaved by “ludicrous beauty standards,” but at least cosmetic surgery wasn’t available to the masses. Forty years later, in a culture where “airbrushed models” and “products to improve our appearance” are everywhere, the authors write, a new and lengthy section is devoted to body image—and how to resist the pressure to conform to plasticized notions of “perfection.”

3. The Introduction of New Terms (and Concepts)

The G-Spot: Though it was first named in 1950, the term didn’t appear in the text until 1984.

Female Ejaculation: It may be a response to stimulation of the G-spot, but this phrase didn’t receive its own section until the 2005 edition.

A guide to "Sex Toys" and a section on "Faking It": New to the 2011 edition.

4. Attitudes Toward Masturbation

From the 1970 text: “Young ladies don’t do that sort of thing.” From the 1992 text: “As infants, touching and playing with our bodies felt good.” From the 2011 text: “It’s common for young children to touch and play with their bodies.”

5. Tone

No longer a feminist rallying cry—an iconic raised fist graced the title page of the original edition—Our Bodies, Ourselves has gradually lost its anti-patriarchal slant. The book’s 1992 edition has a section on “mutual understanding” between a woman and her partner, while the authors of the latest version made a conscious decision to keep “feminism” (at least the use of the word) muted. “The early book was very much a piece of its time,” says Kiki Zeldes, the book’s senior editor. “We’ve put in a lot of work into making sure the new language doesn’t alienate.”