As Huxley was Darwin's "bulldog," so Gribbin and Cherfas have undertaken to bulldog the theories of Berkeley scientists Allan Wilson and Vincent Sarich--who've added a new twist to evolutionary studies by measuring the genetic distance between species. In 1967 they published a classic paper announcing that there was only a l percent difference between human DNA and the DNAs of gorilla and chimpanzee. (The three species are exceedingly close--as close as dogs and foxes, or horses and zebras.) What's more, Wilson and Sarich were able to date their molecular distance measurements, postulating that human and ape species shared a common ancestor as recently as 4(apple) billion years ago. According to the authors (both New Scientist staffers), the 1967 paper scandalized paleontologists who either dismissed it out of hand or advanced arguments that showed how little they understood the biochemical techniques and calculations involved. Thus, the need to champion the cause. Unfortunately, they do this in wearyingly repetitive detail, scoring paleontologists as prejudiced, smug, or beside themselves at the very thought that humankind only recently separated from the hairier animals. When they do provide some reasonably new information, they are proficient, enthusiastic expositors. But the facts are difficult to track down amid the noise.