In order to open windows into the future, contemporary scientists often need to look through windows into the past. On the Shoulders of Giants (PBS, Wednesday, Jan. 22, 8-9 p.m.) is an attempt by one of television's most revelatory science programs -- ``Smithsonian World'' -- to track the process of understanding from one generation to the next: from the 19th-century work of Charles Darwin to the current research of David Steadman.
David McCullough, the knowledgeable and genial host/tour leader of the series, says that Mr. Steadman, a paleontologist and research associate of the Smithsonian Institution and the curator of birds, mammals, and reptiles at the New York State Museum in Albany, ``carries the torch that Darwin first lit.''
Together they track part of the journey of Darwin's famous ship, the Beagle, visiting Gal'apagos Islands, Tahiti, and Mangaia in the Cook Islands, then back to London, where they make a sentimental pilgrimage to Darwin's home.
Throughout the journey, scientist Steadman supplements the gorgeously scenic photography with thoughtful scientific insights into the never-ending process of adaptation and change which take place in nature. He makes it clear to nonscientists how seemingly minuscule discoveries, such as the bones of tiny birds regurgitated by an ancient owl in a subterranean cave he explores, can lead to important evolutionary information.
Another fact that may come as revelation to some viewers: Throughout history and prehistory there were species of fauna that vanished from the face of the earth due to the changing needs of man in the environment. So the danger of species extinction is not a new problem, but a continuing process.
In this third year of ``Smithsonian World'' there has been a bit of a change in the format: Instead of several segments linked together by a universal theme, the program now consists of one major topic investigated in thorough detail. The problem in the future will be to find topics worthy of a whole hour and to somehow develop an identity different from the ``National Geographic'' specials. ``On the Shoulders of Giants'' is, in its gently fascinating way, a tender paean to the scientific method.