As a scientist, Ms. Shapiro has an arm’s-length relationship with de-extinction that very much shapes her book. For years, she has gathered DNA from the fossils of ancient bears, horses and other species—not to bring them back but to learn about what they were like before they became extinct. De-extinction swooped into her life in 2012. The journalist Stewart Brand and his wife, Ryan Phelan, the founders of a genetic testing company, had become fascinated with de-extinction and began reaching out to scientists to see if they would like to explore the possibility. One of the scientists they spoke to was Ms. Shapiro.

Mr. Brand and Ms. Phelan wanted to discuss with Ms. Shapiro whether living animals could be engineered with the ancient DNA sequences she was finding. Ms. Shapiro was curious, and so she shared her thoughts with them. Now she is lending her expertise to de-extinction research as an adviser.

Yet Ms. Shapiro has serious concerns about whether de-extinction will ever actually work. “How to Clone a Mammoth” is thus not a sales pitch or a manifesto. It is more of a thought experiment. If you wanted to clone a mammoth, how would you do it?