She has professed an affinity for black people since she was a teenager, when her parents adopted four black children. She chose a college where she could immerse herself in racial issues. She married a black man and built a reputation as an advocate for civil rights.

Rachel A. Dolezal would hardly be the first person to embrace a racial identity she was not born or raised in, but a rare twist in her story has suddenly turned her into a subject of national debate. Ms. Dolezal, president of her local N.A.A.C.P. chapter and a university instructor in African-American studies, has claimed for years that her heritage is partly black.

And that, her parents say, is a lie.

“She’s clearly our birth daughter, and we’re clearly Caucasian — that’s just a fact,” Lawrence A. Dolezal said in an interview from his home in Montana on Friday. “She is a very talented woman, doing work she believes in. Why can’t she do that as a Caucasian woman, which is what she is?” Ms. Dolezal did not respond to numerous phone calls, emails or knocks on her door in Spokane, Wash., on Friday, but the allegation lit up the Internet, fueled by Ms. Dolezal’s apparent refusal to give a direct answer about her racial background, and by family photos of her as a blue-eyed teenager with straight blond hair.