TORONTO — Paul Bettany says he was initially a bit nervous about starring with spouse Jennifer Connelly in the Charles Darwin film, "Creation."

"It's difficult to come home after a long day and moan about the leading actress if she is your wife," the actor told a news conference at the Toronto International Film Festival, where "Creation" was the gala opener.

"I think we were both a little anxious that we might just sort of laugh at each other. I was 40 pounds heavier and bald so I thought (there was) a lot of reason for her to just laugh at me."

Connelly was more magnanimous.

"It felt like an extraordinary privilege, frankly," she said of working with Bettany, with whom she also co-starred in 2001's "A Beautiful Mind."

"I felt so happy even on a very superficial level to be able to go to work with my husband every day and, you know, sit down next to him in the trailer and put our makeup on together."

"Creation" delves into the internal conflicts that hounded Darwin as he struggled to complete his legendary book "On the Origin of Species."

Bettany stars as the celebrated scientist.

Part psychological thriller and part love story, the tale weaves back and forth in time as a young Darwin slowly comes to terms with the magnitude of his discovery while grieving over the death of his 10-year-old daughter.

His marriage, too, comes under strain as Darwin's scientific theories threaten to shatter the foundations of his wife's religious beliefs.

Emma Darwin, played by Connelly, realizes all too well the societal reverberations that her husband's book could unleash.

This year marks the bicentennial of Darwin's birth and the 150th anniversary of his explosive publication.

The film festival runs until Sept. 19.