What was going on when I was born?

At first glance, the ground inside the ancient redstone wall, bathed in the warm, reflected light of the deep canyon face, revealed nothing but a jumble of stones and dirt. Then Pete Steele, a ranger with the Bureau of Land Management, saw the human bones. ''Man,'' he sighed, ''they've really worked this one over.'' Mr. Steele pointed out a man's pelvic bone, a femur and part of a foot lying in the rubble. Along with a few fragments of skull, they were all that remained of the ancient, pre-Columbian Anasazi Indian grave.

In an unexpected decline, the nation's unemployment rate fell three-tenths of a percentage point in November, to 7 percent, the Labor Department reported today. Except for June 1984, when the rate briefly touched 7 percent, this was the lowest level since President Reagan took office in January 1981. Private analysts, most of whom had expected little or no change in unemployment, said the fresh decline provided reassurance that the sharp slowdown in economic growth since midyear was only a pause and that a recession did not loom. ''It's a promising development,'' said Richard D. Rippe, a senior vice president at Dean Witter Reynolds.

Alfred B. DelBello today announced his resignation as Lieutenant Governor of New York. Mr. DelBello - who has been in public office for 20 years, as Mayor of Yonkers, as Westchester County Executive and as Lieutenant Governor since 1982 - said he was leaving Feb. 1. He will become president of a new company that sells waste-disposal, resource-recovery and pollution-treatment plants to local governments. ''It will offer me and my family the opportunity, maybe, to have a little more normal life than we've had for the past two decades,'' Mr. DelBello said as he made the announcement at a late-afternoon news conference here with Governor Cuomo at his side.

The chairman of the Union Carbide Corporation was arrested today as he arrived in Bhopal and was charged with criminal conspiracy in connection with the insecticide plant gas leak that killed an estimated 2,100 people and injured tens of thousands. He was released on bail six hours later. The chairman, Warren M. Anderson, was arrested along with two senior officials of Union Carbide India Ltd., Keshub Mahindra, the chairman, and V. P. Gokhale, the managing director, who were also charged in connection with the gas leak and remained in police custody tonight. The American company owns 50.9 percent of the stock of the Indian subsidiary. Anderson 'Looked Fine' After his release, the 63-year-old American executive arrived here early this evening on a plane provided by the Indian Government and went directly to the United States Embassy. A diplomatic source there said Mr. Anderson ''looked fine'' and had reported no mistreatment by Indian authorities.

Canada's Progressive Conservative Government today proposed the abolition of many rules that set out to control the type and size of foreign investment in the nation. The tone of the proposal, put forth by the pro-business party, was in sharp contrast to the nationalistic policies of the former Liberal Government under Pierre Elliott Trudeau. Those policies were widely criticized, especially in the United States, which is the largest foreign investor in Canada, as being excessively bureaucratic and frightening away new investors. The new policy ''is saying to the world that we want to encourage as much investment as possible,'' Sinclair Stevens, the Minister of Industry, said. He added, ''When we say we want to dismantle needless barriers to enterprise in this country, we mean it.''

Transcript of news session, page 10. WASHINGTON, Dec. 7 - President Reagan today praised the Treasury's proposal for income tax simplification as ''the best and most complete'' he had seen, but he stopped short of offering it as his own. At the same time, the President came closer to confirming that he might trim the military budget's rate of growth, saying he would ask Secretary of Defense Caspar W. Weinberger to ''see what he can contribute'' to the deficit-cutting package the White House is to propose to Congress. ''There are only two things'' in the budget discussion that cannot be changed, Mr. Reagan said. ''One of them is Social Security and the other is the interest on the debt.''

St. Ambrose stared down from the ornate gold, red and blue tapestry, a whip in one hand and a bishop's staff in the other, as Milan's Mayor handed out honors to citizens of a city whose residents sometimes call themselves ''Ambrosiani.'' He had a stern look, this version of St. Ambrose, a glance that came naturally to the man who put the Christian Church in Milan on its feet in the fourth century. By some accounts, he was a kind of saintly organization man. ''The Roman Empire was in the process of collapsing, the church was the one strong institution, and St. Ambrose set about getting organized,'' said Prof. Giorgio Rumi, a scholar at the University of Milan.

The former second-ranking member of the Solidarity underground and another Solidarity member will be freed under the terms of this summer's amnesty, the Polish television announced tonight. Bogdan Lis, a 31-year-old former shipyard mechanic and former Communist Party member, has been held since his arrest in June, along with Piotr Mierzejewski, a former Solidarity member, while the authorities weighed a case of high treason against them. Such a charge, which carries a death penalty, was specifically exempted from the amnesty proclaimed on June 22 when 652 political prisoners were released. Their release was seen, in part, as a conciliatory gesture toward the West.

Police officers and soldiers sealed off a slum neighborhood with tanks and rounded up more than 5,000 men in house-to-house searches today. The action came after terrorists killed a policeman and bombed a subway station overnight. It was the fourth major sweep of a slum neighborhood since President Augusto Pinochet decreed a 90-day state of siege on Nov. 6 to combat unrest and terrorism against his 11-year-old regime.

Prime Minister David Lange criticized France today for the detonation earlier in the day of a 70- kiloton nuclear device at the French Government's Mururoa Atoll testing site in the South Pacific. ''It does not matter whether the tests are large or small,'' he said. ''What is offensive to New Zealanders is that the French continue their testing at all - despite the unequivocal official and public opposition evident not only within New Zealand, but also throughout the South Pacific region.''

Roland Dumas, a close friend of President Francois Mitterrand, was named Foreign Minister today, replacing Claude Cheysson. Mr. Dumas, a 62-year-old lawyer, was Minister of European Affairs and Government spokesman. The President announced on Tuesday that Mr. Cheysson would become a member of the European Commission, the European Economic Community's executive body. It is a job he held before his appointment as Foreign Minister after the Socialist election victory in 1981.

More than 100 people were shot dead after a guerrilla attack on an army convoy in northwest Sri Lanka, official sources said today. The informants said 102 bodies were recovered from several locations after the attack on Tuesday in Mannar, a coastal district about 185 miles northwest of the capital, Colombo. Initial reports Tuesday quoted officials and residents as saying that as many as 53 people were killed.