In this case, the child is created by a Dr. Frankenstein-type character named Stone. He pulls off the feat by artificially inseminating a genetically altered female bonobo (a bonobo is a type of chimp famous for its propensity to get freaky).
The book, written by Laurence Gonzales, got a pretty tepid review in the New York Times. The reviewer compares "Lucy" unfavorably with another Crichton work:
Mr. Gonzales, who is best known for such nonfiction books as “Deep Survival: Who Lives, Who Dies and Why,” has done a lot of research into bonobo culture and the nonverbal communication of animals, but he doesn’t manage to lend Lucy’s back story even the veneer of plausibility. In comparison, Michael Crichton’s account in “Jurassic Park” (another Frankenstein-ian novel about the wages of scientific hubris) of how dinosaurs were recreated through the use of recovered DNA reads like a report from a respected scientific journal. Not only does Mr. Gonzales fail to explain how Stone might have managed the unprecedented feat of cross-species breeding in the middle of the jungle without any real laboratory or medical facilities, but he also sidesteps the question of why Lucy’s looks are so utterly human and why her bonobo genes are evident mainly in traits like her unusual physical strength and highly acute hearing.
I'm glad to see that the New York Times, like me, was looking for more of a how-to guide.