Not so long ago, 29 years to the day to be exact, black men in the South were killed for allegedly whistling at white women, and segregation laws forced black passengers to sit in the back of buses as white drivers insultingly called them "niggers," "apes" or "black cows."

Yet when one woman, the bone-tired seamstress Rosa Parks, refused to relinquish her bus seat to a white man, she precipitated the Montgomery, Ala., bus boycott that shook the nation. That astonishing movement led by Dr. Martin Luther King Jr. paved the way for civil and voting rights laws that empowered millions, revolutionized attitudes and brought the freedoms we now enjoy.

Looking back on that December day in 1955 when her slap at the face of segregation sent tremors around the world, Rosa Parks feels proud of the progress, particularly because the number of black mayors has soared from six to more than 300. Black elected officials have increased from 300 to 5,000. "But it's not all it could have been," she reminded us. "We still have the differences with us. I'd like to see a place and time where we could live in peace and harmony and not have to dwell on the horrors of the past."

That past has produced many changes in our country, despite the Reagan administration's attempts to roll back the civil rights gains. By contrast, in other parts of the world, they have practically remained the same.

In South Africa, the harsh machinery of apartheid has 200 laws to protect white minority interests and keep the races separate. Blacks cannot vote and have no representation in government. They are forced to be citizens of 10 essentially barren and jobless tribal "homelands." They live in separate townships and must carry passbooks to enter white cities to work. Families are forced apart as men must leave home to work at unskilled and underpaid jobs.

The state spends $95 to educate a black child and $787 to educate a white one.

Black South African leader Steve Biko was killed when he protested conditions. Others, like Nelson Mandela, are kept in jail.

When the new South African constitution took effect on Sept. 3, it gave partial recognition to persons of mixed race and Indians but totally excluded blacks. When blacks protested and hundreds of thousands went on strike on the farms and in the mines, the number killed since September rose to at least 167. In early November, South African officials arrested the strike leaders without bothering to charge them.

The arrest of those leaders became the catalyst that, on Nov. 21, ignited the flame of discontent that had been smoldering within black American leaders for years, just as Rosa Parks' arrest was the catalyst that roused blacks in Montgomery 29 years ago.

"When they swept up the strike leaders," D.C. Del. Walter Fauntroy said in an interview last week, "black America said, 'Enough, enough!' We knew we had to humble ourselves and go to jail."

America provides two ways to affect public policy: through the ballot, and through the First Amendment right to assemble peaceably and protest.

"The Congressional Black Caucus tried to bring change with the Gray Amendment that would have halted new South African investment by American companies," said Fauntroy. "That amendment passed the House but then it was killed in the Senate at the behest of the Reagan administration.

"It was then that Randall Robinson head of TransAfrica and the new "Free South Africa Movement" said, 'We've got to do something.' We got together and said it is time to move to a new level."

That "new level" is unfolding each day outside the South African embassy. It is the beginning of ongoing anti-apartheid protests in which several black and white civil rights leaders, labor leaders and elected officials have gone to jail. They are calling for the release of the South African strike leaders and other political prisoners. They want good faith negotiations between legitimate black leaders and the South African government and a halt to the Reagan administration's policy of "constructive engagement" with South Africa.

It took a year-long boycott to change Montgomery, Ala. It took years of protest to change America. With the moral imperative and zeal of those who now protest against South Africa, it is certain that the inhumane system of apartheid will one day be transformed as well.