Y: The Last Man, Vol. 9 Motherland

From back cover:
Finally reunited, the last two males on Earth -- Yorick Brown and his pet monkey Ampersand -- are on a slow boat to China, heading for a long-anticipated reunion with Yorick's lost fiancee in Paris. But while the pair are getting ready to cross two more continents with their longtime protector Agent 355, their other traveling companions -- biochemist Dr. Allison Mann and her girlfriend Rose -- are nearing the end of a different quest: finding out what caused the plague that wiped out every other mammal with a Y chromosome fours before.
What they find, in a hidden lab in Hong Kong, is something that none of them expected -- something that could mean the end not just for the Last Man, but for any future his gender might have.