As National Geographic editors prepared an issue dedicated to race, they realized the 120-year-old magazine might face questions about its troubled history on the subject.

So they asked John Edwin Mason, a University of Virginia professor who studies the history of Africa and photography, to dig through the magazine’s archives to examine its shortcomings in covering people of color in the United States and abroad.

He was unsparing.

“Through most of its history, National Geographic, in words and images, reproduced a racial hierarchy with brown and black people at the bottom, and white people at the top,” Mason said.

There was a complete absence of urban, educated Africans in the magazine, he told them. Black people were presented as static, primitive and non-technological, often unclothed or presented as savages, he said. And that image, which persisted until the 1970s, shaped how the magazine’s readers — largely white and middle class — perceived black people, he said.

But as he presented his findings to the editors, he didn’t encounter the kind of defensiveness he feared, he said. Instead, they gave his research prominent placement under a headline with no equivocation: “For Decades, Our Coverage Was Racist. To Rise Above Our Past, We Must Acknowledge It.”

Written by Susan Goldberg, the editor-in-chief, the note acknowledges that “it hurts to share the appalling stories from the magazine’s past.” It includes some of the most blatant examples of racism, including a 1916 story about Australia that included the photo caption: “South Australian Blackfellows: These savages rank lowest in intelligence of all human beings.”

Goldberg said Tuesday that the magazine was proud of its history of opening eyes to new places and cultures, and of the way the publication has grown in recent decades.

But she said the magazine, which won a National Magazine Award on Tuesday for an issue dedicated to gender last year, hoped that coming clean about its mistakes would help gain some credibility.

“It tells people that you’re thinking about these things, you care about these things, and you want to do a better job,” she said.

Deborah Willis, the chairwoman of the Department of Photography and Imaging at New York University, said she grew up reading National Geographic, but had long noticed the failure to capture the voices of black subjects. She never heard how they felt about being photographed or the story behind their jewelry; instead, you heard the “voice of the institution,” she said.

“I wanted to become a photographer because of National Geographic,” she said. “I wanted to tell a different story.”

Modern news organizations still lag in minority representation on photography staffs, said Brent Lewis, a senior photo editor at ESPN’s the Undefeated. Lewis praised National Geographic’s overall effort, but said he was disappointed that the cover — the most recognizable image for an issue dedicated to race — was shot by a white man, Robin Hammond.

Goldberg said the main story featured nine photographers, five of whom were people of color. Of the eight writers, four were people of color.

“We cover a diverse world,” she said. “If we want to do so accurately and with authority, we need a diverse staff to cover it.”