The Passionate Ape, 2001 by Craig Hagstrom (pdf version)
This is a brilliant book. Free pdf download here: PassionateApe.com
The Passionate Ape. Bad Sex. Strong Love, and Human Evolution. by Craig Hagstrom.
Starting from the Aquatic Ape hypothesis, this work outlines the selective pressures and processes which could move an ape from land to an aquatic life and back. Using primate morphology, it shows why apes make poor aquatics that are prime candidates to return to land when conditions permit.
It uses Great Ape behavioral traits to describe the mental constraints on such evolutionary moves, and to show how the land-water-land transition would in turn shape our mental evolution. The major focus is on mating issues and sexual dysfunctions caused by these transitions, and how our coping mechanisms became vital assets setting us apart from the other Great Apes.