Long Synopsis:
Paul is the gravitational pull on his college friends who have somehow stayed in his orbit for nearly a decade, meeting every summer for a weekend at his mother's house in upstate New York. This year, Paul makes a desperate attempt to keep everyone together. His friends don't cooperate. And everything reminds them of how far they have, in fact, not come.

ORIGIN OF THE SPECIES starts as a parable of human evolution and develops as a lighthearted drama. Paul has prepared menus and conversation topics circling the question of how a species evolves. Sex is the catalyst, but sex is only the beginning.

Paul's wife, Julia, is ambivalent about being pregnant and has not yet told him about the pregnancy. When she finally does, Paul seems completely out of touch with her emotions, jeopardizing the future of their relationship.

Stan has recently survived testicular cancer, but he's far from feeling alive. Kate, Stan's ex-girlfriend, abandoned him during his illness. Now Kate discovers that her friend Laura has designs on her former lover. Laura, ostensibly the least successful and least sexy, offers the most compassion and insight. Stan's doctor has told him that sex, in his case, is medically uncertain. Kate tempts him with sex. Laura teaches him about love.

Fisher, the consummate player, loses patience with his friends, especially Paul. Fisher is surprised to find that Julia sometimes shares his feelings. The two take a morning outing to a country donut stand where their flirtation becomes a betrayal.

When Paul reveals his biggest biological find, the story of a recently discovered primate species, the Bonobos, the annual skinny dipping ritual becomes a ritual in a deeper sense. They learn the lesson of an evolutionary ancestor: sex is only a step on the way to truly loving one another.