‘How and Why’ explores issues of biology, and much more

Nature and nurture are in conflict in “The How and the Why” — and not just the central conflict about female evolutionary biology at the heart of this cerebral two-character drama now making its Bay Area premiere at the Aurora Theatre.

The title of Sarah Treem’s play refers to a scientific approach to explaining how things work — that mechanics and function, equally weighted, go hand in hand — and this principle may be the only point of agreement for Zelda (Nancy Carlin) and Rachel (Martha Brigham), two biologists meeting for the first time in Zelda’s comfortable academic office.

Zelda’s an established, middle-aged scholar whose greatest triumph was a theory on menopause published decades earlier.

Rachel, a whip-smart graduate student, is eager to advance a new theory on menstruation — one that’s closely related, but appears to threaten the validity of Zelda’s point of view.

Treem begins to load the language long before approaching the central argument. Rachel, casting a wary eye over Zelda’s workspace, calls it “masculine.” Zelda offends Rachel by asking about the younger woman’s relationship status, curious as to why she hasn’t yet married.

Science and feminism, men and motherhood, and the poetry of Edna St. Vincent Millay thicken the debate, and what starts as a potential mentoring begins to call both women’s positions into question. When Rachel, sponsored by Zelda, is humiliated at a prestigious national conference, their uneasy alliance seems to approach a perilous point of no return.

Tightly staged in the Aurora’s intimate Harry’s UpStage performance space, with handsome set and lighting by Kent Dorsey and age-defining costumes by Christine Dougherty, the play gradually reveals the characters’ concealed grievances, expectations and vulnerabilities.

As the political becomes personal, Treem builds a heightened sense of each woman’s stakes in the outcome.

If the dialogue gets a little too dense in spots, the sharp performances carry it through. Carlin is superb as lofty, logical Zelda, shading the character with humanity and the dawning realization of how much her dedication to the pursuit of science has cost her over the years. Brigham’s bright, contentious Rachel is a fascinating mix of fierce idealism and childish fears.

The director is the redoubtable Joy Carlin – Nancy Carlin’s mother – adding an aptly expert touch in a play that puts motherhood and other women’s issues center stage.

The How and the Why
Where: Harry’s UpStage, Aurora Theatre, 2081 Addison St., Berkeley
When: 7 p.m. Tuesdays, 8 p.m. Wednesdays-Saturdays; 2 p.m. Sundays; closes May 22
Tickets: $35 to $45
Contact: (510) 843-4822, www.auroratheatre.org