One in four male South Africans surveyed admitted to committing rape, according to a research group.
The government-funded Medical Research Council, whose findings often influence official policy, said it conducted the survey to deepen understanding of men's attitudes and behavior.
The finding has cast a harsh light on a culture of sexual violence that victims groups say is deeply embedded in society.
According to police statistics, some 36,000 women were raped in 2007 — nearly 100 per day. But victim support groups and government-backed research say the vast majority of rapes go unreported because of the stigma and trauma involved. South Africa is home to about 50 million people.
Chief researcher Rachel Jewkes said Friday that the findings were "shocking" but "not unexpected." Opposition political parties said they were horrified, but victim support groups said they were not surprised.
"The report indicates that rape has become 'normalized' as a feature of masculine identity in a society that has emerged from years of oppression — a tragic development for both women and for men," said Anne Marie Goetz, chief of the Governance, Peace and Security section of the United Nations Development Fund for Women.
"The implications of this are grave for women's security but also for long-term development, which relies upon deepening gender equality," Goetz said.
South Africa's newly installed president, Jacob Zuma, has made combating crime one of his top priorities and has set up a new ministry to promote women's and children's rights.
The government had no immediate comment, but the study is expected to be one of the focal points of a conference on sexual violence early next month.
"Rape is a crime of a sense of entitlement. It comes from a notion of power," Jewkes said, adding that South Africa's male dominated cultural traditions were partly to blame.
"I don't think there is a quick fix," said Jewkes. "If people were concerted about trying to fix it, it would take a generation."
Researchers interviewed men from just over 1,700 households from a cross-section of the population in the rural provinces of the eastern Cape and KwaZulu-Natal.
The survey gave no margin of error. The research council is internationally respected and regarded as reliable. It said it surveyed a representative cross-section of men of all races in the two provinces, which are representative of South Africa.
It was not immediately known if any comparable surveys on this sensitive topic have been published. Sexual abuse is rife in a number of African countries but none have the sophisticated survey methods of South Africa, and in some other countries it is a taboo subject.
Nearly 28 percent of men interviewed said they had forced a woman or girl to have sexual intercourse against her will, according to the survey. It said that 14 percent said they had raped a former or current girlfriend; 12 percent said they had raped someone who was not their partner; and 10 percent said they had raped both a stranger and a partner.
The research council survey said that nearly 20 percent of those who admitted sexual abuse had the AIDS virus — only slightly higher than the 18 percent infection rate among men not involved in rape.
It said that 17 percent of the men surveyed admitted to attempted rape, and 9 percent said they had taken part in gang rapes. In all, 42 percent of men surveyed said they had been physically violent to an intimate partner (current or ex-girlfriend or wife), including 14 percent in the past year.
"Our study suggests that the pathway which leads to these ideas and the practices of rape and other forms of violence toward women starts in childhood," said Jewkes, head of the research council's gender and health unit. She said the results backed up findings of earlier research among younger men.
She said that "rape is far too common, and its origins too deeply embedded in ideas about South African manhood," for it to be regarded merely as a criminal problem which could be solved by prosecuting the rapists.
"You can't change behavior practiced by one quarter of the population if the main strategy is through the use of police and courts," Jewkes told The Associated Press. "The police and courts are important but they are only part of the solution."
Many victim support groups complain that rape cases are repeatedly postponed and little is done to protect the woman from the trauma of facing her tormentor. Most cases don't even reach court.
"Rape is one of the most brutal human rights violations in the world," said Maria Jose Alcala, who heads the U.N. development fund's effort to curtail violence against women. "It is a stark manifestation of just how little value our societies place on the lives and dignity of women and girls."
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