Nature's Nether Regions by Menno Schilthuizen is one of seven books up for The Bookseller's annual award.
Menopause memoir The Madwoman in the Volvo: My Year of Raging Hormones and Divorcing a Real Witch - a practical guide for ending pagan relationships - also make the list.
The winner will be named on 27 March.
Also nominated is Where do Camels Belong?, an investigation of the species, and The Ugly Wife is Treasured at Home, an expose of love and sex under Maoist rule in China.
Strangers Have the Best Candy, an account of speaking to strangers, and the academic papers from a two-day symposium of concrete pavements - Advanced Pavement Research - complete the shortlist.
"This is one of strongest years I have seen in more than three decades of administering the prize, which highlights the creme de la creme of unintentionally nonsensical, absurd and downright head-scratching titles," said The Bookseller's Horace Bent.
"Ultimately, it is a stunning collection of books. Let other awards cheer the contents within, the Diagram will always continually judge the book by its cover (title)."
Members of the public can vote for their favourite on We Love This Book by 20 March.
There is no prize for the winning title, but the person who nominated it will receive a "passable bottle of claret".
Last year's prize was won by Mats and Enzo's How to Poo on a Date, with previous winners including The Big Book of Lesbian Horse Stories, Cooking with Poo and Living with Crazy Buttocks.
A book about the evolution of genitals has been shortlisted for this year's Diagram Prize for the oddest book title of the past year.