What was going on when I was born?

IN Brooklyn a young mother threw her hours-old baby out of an apartment window to the street 18 floors below. In Tokyo the corpse of a newborn child was abandoned in a coin locker in a railway station. In Manhattan a father beat his 3 1/2-month-old son to death. These are a few of many reported cases of infanticide, the most vicious form of child abuse. It is a human crime so abhorrent and disturbing that little has been written about it, and it is behavior so mystifying that scientists are still far from fathoming its underlying causes. Scientists agree that the history of human infanticide probably goes back to the cave. Records from medieval times show that a parent would kill either male or female infants, depending on which sex was needed more in society at a particular time in history. And in some primitive cultures today infanticide is not an uncommon practice.

A senior Navy admiral has questioned the legality of a $4 million fee that the McDonnell Douglas Corporation plans to pay a Spanish consultant for helping to sell F-18 jet fighters to the Spanish Government. Vice Adm. E.R. Seymour, the head of the Naval Air Systems Command, said in a Feb. 5 letter to the Chief of Naval Operations then, Adm. Thomas B. Hayward, that the terms of an agreement between McDonnell Douglas and its Spanish agent, Compania Aeronautica Espanola, appeared to exceed limits set by Government regulations. The main issue centers on whether the payment to the agent is made out of the company's profits or whether it is counted as part of the price of the $3.1 billion contract that is being financed with Government credits.

The United States and China have signed a new communique governing both countries' relations with Taiwan. Administration officials say the document should prevent a major rift with Peking. In the communique, expected to be made public on Tuesday, China pledges to seek reunification with Taiwan only by peaceful means, and the United States promises not to exceed current levels of sales of fighter aircraft to Taiwan and to reduce them gradually. John H. Holdridge, the Assistant Secretary of State for East Asian and Pacific Affairs, gave unpublicized briefings this morning to Senate and House leaders in advance of the public announcement of the new development in Chinese-American relations.

Scientists, using a combination of machines and detectors built on a monumental scale, are now ready to launch into a whole new world of physics. In scope and complexity, their project bears much in common with man's missions into space. The goal is to find what the scientists refer to as the missing ''keystone'' in the family of particles that seem to constitute and control matter at the most basic level. The celebrated keystone is a triplet of particles that, it is believed, will fit into what otherwise appears to be an orderly theory of matter and the universal laws that govern it. These three relatively massive, though elusive, particles are known as W+, W-, and Z0.

Philip C. Habib, the special American envoy, began trying today to resolve what were described as relatively minor differences blocking a final agreement on evacuating Palestinian guerrillas from west Beirut. Mr. Habib returned here from Jerusalem and briefed Prime Minister Shafik al-Wazzan of Lebanon on the latest Israeli concessions in the negotiations. The Prime Minister told reporters that he expected the remaining issues to be resolved shortly and ''implementation'' of the Palestine Liberation Organization withdrawal to begin this weekend at the latest. Mr. Wazzan said that ''differences have now narrowed to the point where they have almost disappeared.'' (In Jerusalem, a ranking Government official said the return of an Israeli pilot and the bodies of nine soldiers was the only issue that remained unresolved, adding, ''All other obstacles have been swept away.'' Page A16.)

The Army Corps of Engineers will lose more than half the inspectors responsible for monitoring illegal dumping into New York Harbor and for keeping the harbor's major navigation lanes clear, senior officials of the corps said yesterday. The officials said that no other state or Federal agency would take over these responsibilities and that they would have to rely on increased public cooperation in reporting harbor hazards. The cuts, which will go into effect on Sept. 26, came after the Federal Office of Management and Budget ordered the Army agency to reduce costs. They will result in the transfer, retirement or laying off of 14 of the 26 inspectors who work primarily in New York Harbor.

Saturday Review magazine suspended publication yesterday after losing $3 million in a two-year effort to reinvigorate itself as a monthly journal of cultural news. Although its owner, Robert I. Weingarten, said he was hopeful that someone might step in later this week with money to buy and run the 58-year-old publication, he acknowledged that the chances of a revival were slim. The staff of two dozen employees has been furloughed, and many of them were busy yesterday packing their files and preparing to look for other jobs. At the peak of its influence in the 1950's and 1960's, what was originally christened The Saturday Review of Literature gave a weekly audience of 630,000 subscribers a lively mix of reportage and essays about society and culture. Norman Cousins, the editor from 1939 to 1971, made ''S.R.'' a reflection of his own wide-ranging tastes and curiosities, exploring such topics as disarmament and environmental protection long before they became fashionable causes.

''We are within sight of the safe port of economic recovery. Do we make port or go aground on the shoals of selfishness, partisanship and just plain bullheadedness?'' - President Reagan. (D16:6.)

An F.B.I. agent testified in a Manhattan trial yesterday that he had posed as ''a high-rolling hoodlum'' who operated a drinking club as part of a major undercover investigation that had infiltrated organized crime. The agent, Edgar S. Robb, said he had used the name Tony Rossi in his undercover work with another agent, Joseph D. Pistone, who testified earlier in the trial of five men on racketeering charges in Federal District Court. Mr. Robb testified that one of the defendants, Benjamin (Lefty) Ruggiero, became his ''partner'' in operating the Florida drinking club, which was actually the principal base for the undercover operation by the Federal Bureau of Investigation. ''You now have peace of mind,'' the agent said Mr. Ruggiero told him when they became partners. ''But it's going to cost you.''

The Cities Service Company last night spurned a takeover bid made Friday by the Occidental Petroleum Corporation but invited Occidental to make a better offer. In a statement released after a 3 1/2-hour special meeting of the company's directors, Cities Service said that its board had concluded unanimously that the Occidental offer ''would not meet the board's objective of maximizing value'' for the company's shareholders. The response was conveyed in a letter addressed to Dr. Armand Hammer, chairman of Occidental, by Charles J. Waidelich, chairman of Cities Service. An Occidental spokesman, who asked not to be identified, said late last night that Dr. Hammer was still studying the Cities Service reply and was not yet ready to respond.

Shaken by the disarray that has followed Mexico's second major devaluation in less than six months, foreign bankers now seem unwilling to provide the Government with new credits before President Jose Lopez Portillo leaves office in December. By paying wider spreads - that is, higher interest rates than previously - the Government had succeeded in borrowing $6.5 billion of $11 billion needed for 1982 before the latest crisis erupted. But Finance Minister Jesus Silva Herzog flew to Washington last weekend for talks with the International Monetary Fund and the Federal Reserve Board concerning possible borrowings from those agencies, in effect conceding that commercial sources of credit had dried up. ''The whole idea of new loans is academic for the moment,'' said one American banker who, like other bankers interviewed, asked to remain anonymous because of the sensitivity of the subject. ''Even wider spreads wouldn't make much difference at this juncture. Everyone is waiting for the new Government.''

International A final accord on a P.L.O. pullout from west Beirut is being delayed only by minor issues, parties to the agreement said. The differences between Lebanon, the P.L.O. and and Israel have narrowed to the point where they have almost disappeared,'' Prime Minister Shafik al-Wazzan of Lebanon said. He made the remarks after a briefing by Philip C. Habib, the special United States envoy, who returned to Beirut from Jerusalem. (Page A1, Columns 1-2.) Egypt has again told the United States that it will not accept any Palestinian guerrillas evacuated from west Beirut unless the Reagan Administration makes a commitment to bring about an overall Middle East settlement, including self-determination for the Palestinians. In messages to the United States charge d'affaires in Cairo, Egypt also said it would not consider a resumption of suspended talks with Israel about Palestinian autonomy as long as Israeli forces remain in Lebanon. (A17:1-2.)