Play explores links between women and science and two women of science

PRINCETON - Attention, all Darwinians. Attention, Mercedes Ruehl fans. Attention, fans of HBO's

In Treatment

. Attention, everybody who's interested in serious drama about serious ideas.

The new play at the McCarter Theatre, The How and the Why by Sarah Treem, directed by Emily Mann, is supersmart, super-engrossing, and an altogether super production.

This is a two-person play - all talk, no action - about science. One of the two persons talking is Zelda Kahn (the always superb Ruehl), a famous biologist whose "Grandmother Hypothesis" launched her career 30 years ago. It explains how humans differ from other primates and why a woman's reproductive life ends before her natural life.

The other talker is young biologist Rachel Hardeman (Bess Rous) - difficult, prickly, and conflicted about her role as a woman in this competitive-men's world. Her idea, opposed to the "Grandmother Hypothesis," is the "Menstruation as a Defense" theory. In the course of the play, we will learn a great deal - painlessly - about evolutionary biology.

The ostensible occasion of their meeting is a major conference, "the Olympics of Biology," while the relationship between the two women, both personally and professionally, is the play's real subject. This involves generational issues (attitudes toward sex, marriage, childbearing, feminism, careers) as well as their private issues (parents, lovers). There isn't a woman who won't recognize herself, nor is there a man in the audience who won't learn something about women.

Playwright Sarah Treem, though only 29, is experienced at two-handers as a writer and producer of the series In Treatment, about a psychiatrist and his patients in therapy sessions. Director Mann makes riveting and suspenseful what in lesser hands would be a static, too-talky play.

The two actors can deliver very complex material, not only with naturalness and ease, but also with the speed appropriate for one scientist talking to another. Even more important (after all, this is a play, not a lecture) is that each actor creates an in-depth portrait, building her character with body language and gestures, quirky physical clues to personality and temperament.

As always, McCarter's staging is top-notch: The two sets (a posh academic office and a grungy university town's bar) were designed with perfect attention to detail and atmosphere by Daniel Ostling. Hardeman: "I like your office. . . . It feels very . . . masculine." Kahn: "You mean it feels significant." And we're off.

The How and the Why provides a glimpse into the thrill of working on groundbreaking science: "You might stumble across even the smallest secret of the universe. And for a moment, this new truth will be known only to you. We are explorers, you and I. . . ."

The meaning of the play's title extends far beyond the standard description of scientific inquiry into phenomena; the how and the why are exactly the questions drama seeks to answer.

Through Feb. 13 at the McCarter Theatre, 91 University Place, Princeton. Tickets $20-$70. Information: 609-258-2787, 888-278-7932, or www.mccarter.org.EndText