CABLE DEPLOYS TWO WEIGHTY SCIENCE PROGRAMS THIS WEEK. A&E PRESENTS Dinosaur! over four consecutive nights, beginning Sun., Sept. 8, at 8 P. ET. The major flaw of this informative if discursive series hosted by Walter Cronkite is that it dwells too much on a dry history of paleontology and too little on the mammoth creatures who ruled our roost for 150 million years. The Discovery Channel has People of the Forest (Sun., Sept. 8, 9 P. ET), a fascinating 20-year study of chimpanzees in Tanzania. The life's work of Hugo Van Lawick, ex-husband of Jane Goodall, the footage is woven into a poignant story of loyalty and individuality by Donald Sutherland's narration.