In marine mammals’ battle of the sexes, vaginal folds can make the difference
Patricia Brennan has made a splash with her studies of genitalia and fit
![harbor porpoise](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2017/12/122317_notebook_scilife_main.jpg?fit=860%2C460&ssl=1)
FERTILE FOLDS In harbor porpoises (one shown), females have vaginal folds (3-D endocast shown below) that may help them exert control over fertilization.
Solvin Zankl/Alamy Stock Photo