San Francisco — Tug of war, town planning, croquet, poetry, and Australian football have - Olympically speaking - followed the carrier pigeon and the dodo into extinction. Over the last century, gold medals have been awarded in all of these unlikely events. In fact, since 1900 nearly 50 other now-obsolete Olympic sports have been tested and scrapped for various reasons. Next summer in Los Angeles, athletes from more than 150 countries will compete in 23 Olympic events. But one might well ask in which events they will not be competing - the rope climb, one-handed weightlifting, and pelota, the Spanish version of jai alai.
We remember the Jim Thorpes, the Jesse Owenses, and the Olga Korbuts. But who recalls the Schmid brothers of Germany winning an Olympic gold for the fastest time scaling the north face of the Matterhorn?
And what about Australian Frederick Lane's 1900 Paris victory in the 200 -meter obstacle swimming course - over barrels, under boats, around piers and buoys?
Or Frenchman Charles de Vendeville, who stayed submerged in the Seine for 68 seconds to win a gold in the ''underwater swimming'' event.
And does anybody remember - or care to remember - the names of the winners in such now-defunct Olympic events as musical composition, fishing, and ''the firing of large-caliber cannons and aerostation''?
To be sure, Los Angeles's XXXIII Olympic Games next summer will bear little resemblance to its namesakes in 776 BC, when the Panhellenic world gathered at Olympia and runners were awarded not only olive wreaths, statues in their honor, and free feasts for a month, but also lifetime exemption from taxation.
But next year's Games also bear a less-than-perfect resemblance to Games within the last century. Like rising and falling hemlines, the Olympics are susceptible to fad and fashion, and the turnover in events is astonishing. Fewer than half of the 1984 Olympic events were held in 1896, when Baron Pierre de Coubertin, father of the modern Olympic Games, assembled more than 300 athletes from 13 nations in Athens and awarded olive wreaths for the first time in 14 centuries.
At that time, there were no team sports - no basketball, field hockey, volleyball, or handball. There were no women's events. Sailing, kayaking, judo, and the pentathlon, of course, were not included. Nor, for that matter, was windsurfing. It will be introduced next summer.
Even today, the standard for selecting Olympic events is imperfect and often subjective. ''Generally, the committee considers how widespread the sport is, how many continents play it, and how many countries belong to the international federation of that sport,'' says Andrew Strenk. The resident historian on the staff of the 1984 International Olympic Organizing Committee in Los Angeles, Dr. Strenk swam the 1,500-meter freestyle at the 1968 Games in Mexico City. And until recently, he taught modern European history at his alma mater, the University of Southern California, which boasts more Olympic alumni (over 200) than any other US university.
A sport like cricket, Strenk explains, ''may be an international sport, but is not played widely enough.''
The choice often comes down to dollars - and business sense. ''Behind the scenes,'' says Strenk, ''the committee has to ask how many people will watch the sport, can we sell out the stadium, is it adaptable to television?''
Sports also have a way of getting tangled in the political thicket, adds Strenk, who wrote his doctoral dissertation on the politicization of international sports. Lawn tennis, for instance, was played in the Olympics between 1896 and 1924, when it was dropped because of what Strenk calls ''bureaucratic politics.''
At that time, he says, the International Olympic Committee (IOC) ''wanted to damp down'' Wimbledon, which was stealing Olympic thunder. The committee asked the International Lawn Tennis Federation to cancel the annual British tournament. When the federation refused, the IOC gave tennis the boot. The growth of the pro tennis circuit in the 1930s only confirmed the IOC's concern over corrupting amateur competition. The committee, in fact, seemed to echo the warning of Euripides, the Greek tragic poet (and athlete) who wrote that ''Out of tens of thousands of ills in Greece, none is worse than the tribe of professional athletes.''
What became a ''political battle for control of tennis,'' says Strenk, has since simmered down. In 1984, tennis returns as a ''demonstration'' sport in Los Angeles. It will become an official event at Seoul in 1988.
A handful of other now-extinct Olympic sports have had long, respectable lives. One was the 2,000-meter tandem bike race, held from 1908 to 1972. More often, however, the events last only a single Olympiad: Indian-club swinging in St. Louis (1904); motorboating 40 nautical miles on the Thames in 1908 (only one boat in each of three classes finished); gliding and field handball in Berlin ( 1936); Australian football in Melbourne (1956). In 1932, when the Olympics were last held in Los Angeles, lacrosse and American football were demonstration sports. Neither survived.
But surely one of the most exciting (if contentious) of those sports was the tug of war. Unlike track and field, where time elapsed and pounds lifted marked the winners and losers, the tug of war had fuzzy rules. It was embroiled from the start in controversy over grips, tactics, and the weight and number of contestants. But it was a folk sport, surviving the Olympic Committee's discretion because of sheer crowd appeal.
And no Olympic tug of war is more infamous than the 1908 ''Battle of Shepherds Bush'' - a reference to the stadium in which the London Games were held that year. As was its custom, Britain entered the Liverpool police force in the competition that year. The bobbies showed up in heavy leather boots - much to the chagrin of the Americans and Swedes, who cried foul. The Swedes and British nearly came to blows over the matter, and the referees ruled in favor of the home team. At the 1912 Stockholm Games, however, the Swedes were waiting with their own police team - and their own referees. They won both the gold and sweet revenge.
Sports mythology still holds that the length of the modern marathon derives from the distance between Athens and Marathon (about 40 kilometers), which the famous courier ran nonstop to announce the defeat of the Persians.
Not so. It was the distance between an Olympic stadium and a royal kindergarten.