“Trumpery” is not the first foray into science for Mr. Parnell, a screenwriter and dramatist who has worked on television shows like “The West Wing” and who teaches television writing at the Yale School of Drama. That would be “QED,” a play about Richard Feynman, the physicist and theorist of quantum electrodynamics, the modern theory of electromagnetism.

It was while working on that play that Mr. Parnell stumbled on a book, “The Song of the Dodo” by David Quammen, which describes Wallace’s work. The book led Mr. Parnell to more study of Darwin, Wallace and their times. Pretty soon, he had a three-act play with, he realized, a cast of way too many characters dealing with way too many subjects  not just evolution, but topics like Colonialism and a Tierra del Fuegan accused of murder.

Image Michael Cristofer, top and above left, as Charles Darwin in Trumpery, and Manoel Felciano as Alfred Russel Wallace. Credit... "Trumpery” photographs by Sara Krulwich/The New York Times

“I didn’t know for a long time what the play was about,” he said.

But just as “QED” focused sharply on Feynman, Mr. Parnell found this play by focusing on Darwin and telescoping some of the events in his life to bring his quandaries into sharp relief.

For example, much of the play is an argument involving Darwin, his biological allies Joseph Hooker and Thomas Henry Huxley, and their foe, Richard Owen. In fact, their debates took place in letters. But confrontation is useful for a dramatist dealing with science.

“The ideas have to be accurate, they have to be intelligible,” Mr. Parnell said. “But you have to find a dramatic way to tell it  a reason it can be a play, to exist on stage.”

He added, “It has to be grounded in conflict.”

“Trumpery” is not Mr. Parnell’s first exploration of a frightening idea either. That was “And Tango Makes Three,” a children’s book he wrote with his partner, Justin Richardson. The book tells the true story of Silo and Roy, two male penguins at the Central Park Zoo who courted each other and formed a relationship. When a keeper saw them trying to incubate a rock, he gave them an orphaned egg, which they cared for until it hatched as the chick Tango.