NOT MANY AUTHORS can spend the time and travel money to do what David Attenborough did in order to write Life on Earth. He clambered up a 100-foot high pyramid of guano, over a carpet of glistening cockroaches, to observe a few hundred thousand bats in a Borneo cave. He pushed into unexplored New Guinea to converse in gestures with a primitive tribe never before seen by white men. He dove into the blue waters off Hawaii to listen to the singing of the hump-backed whales --a sound that "penetrates your body, making the air in your sinuses vibrate in sympathy, as though you were sitting within the widest pipe of the largest cathedral organ."

Attenborough could afford all this because he was out primarily to produce and narrate a television series which has been wildly successful in England (and will be seen here on PBS starting in January). His book is the best kind of spin-off--literate, witty, full of earthly marvels presented without any of the orotund self-consciousness of some cosmic TV guides. The purpose of Life on Earth, like its title, is grandiose: to show how today's creatures and plants evolved from the earliest ones. The method, however, is modest. The chapters go along from protein molecules to medusae, from algae to conifers, narrating more than analyzing and pausing from time to time to remark, for instance, that squid have the biggest eyes (a foot-and-a-half across) in the world. Or to reassure us that the earth can never be taken over by outsized sci-fi ants or wasps because an insect's tracheal breathing system would not support such monstrous dimensions. Or to explain that rabbits eat their food twice, first excreting it half digested, then swallowing it again to get all the nourishment out of it, a fact polite nature books never mention.

In some ways, Attenborough goes back to the 19th- century nature sentimentalists. He gives an almost idyllic account of the crocodile's parental concern. The female, hearing a piping call from the eggs she has laid in the Nile sands, lumbers over, picks up the hatching young in her jaws. "Using her huge teeth as gently and delicately as forceps . . . she carries them down to the water and swims away with her jaws half-closed, the young piping and peering through the palisade of teeth" to a nursery area where the young spend a couple of months "hiding in small holes in the bank, hunting for frogs and fish while their parents laze in the water close by, keeping guard." He describes communal life in a prairie dog town: "Citizens move about the town wandering into one another's areas. If a stranger approaches a resident, the animals cautiously exchange a rather reserved kiss . . . and then inspect one another's anal glands to see if they are actually acquainted. . . . If they discover that they are members of the same coterie, then they kiss open-mouthed." Such unabashed anthropomorphism will make a proper scientist squirm, but the beguiled reader should know enough not to take this all too literally.

Attenborough's style is clearly attuned to the telly, making legerdemain transitions that are more subliminal than sensible. Though the book succeeds in its purpose of tracing many family trees, the sum of its parts is much more than the whole. A reader is likely to remember the famous fossil fish, coelacanth, less for its place in an evolutionary line than for the use fishermen make of its tough scales--to rub down inner tubes when fixing punctures. The images in the text are enhanced magnificently by the many color photographs: the battle between a beautifully-fringed sea slug and what looks like an interplanetary jellyfish; the petrified delicacy of fossil insects limned in a ridge of Canadian shale; a boggle- eyed Panamanian tree frog looking like one of Kermit's kin, and a doleful pair of mating newts looking as if they need some amphibian Alex Comfort to instruct them in the joys of sex.

Life on Earth ends with a brisk, offhand chapter on man and, in a way, hands the job over to another popularization which also has a grandiloquent title and a TV connection. The Making of Mankind is by Richard E. Leakey, member of the renowned family which has made epochal fossil discoveries about man's ancestry. The first part of the book takes up the work that the author is most familiar with, the lineage of apes and men. Then, leaving his own special field, he launches into a clear, encompassing survey of the work done in anthropology up to the advent of us, homo sapiens. He and his researchers have read widely and eclectically and whole chapters are based on the work of other scientists, liberally quoted and credited. In fact, the book seems to populate the whole world with fervent anthropologists, digging and sorting and asking tantalizing questions with ever-changing answers.

As a working field man, Leakey has an acute appreciation of the imaginative drudgery that leads to important conclusions. A laborious but shrewd study of a cache of stone-age tools, all chipped in the same inimitable way, demonstrated that at least one prehistoric community employed a master tool maker. Marks on a fossil horses' teeth were found to match those made by today's horses which, when tethered, idly chew on hitching posts, thus suggesting that early men domesticated their horses.

The Making of Mankind moves spryly through the eons, lightening its text with homely facts and fine illustrations. Specialists may complain of gaps and Leakey fans, who enjoy the family's disputatious temperament, will be let down by the book's blandness, especially as regards Lucy. Lucy is the famous three million-year-old anthropoid discovered by the American Donald Johanson who claimed in a best selling book that she was the common ancestor of apes and forerunners of man, including those discovered by the Leakeys. Richard Leakey was reportedly furious at this challenge to the family's preeminence and used that somberly damning word "incautious" in referring to Johanson.

But now in his book he simply says that Lucy "provoked a good deal of discussion" and laughs off reports that there is any "controversy" between them--though, of course, he thinks Johanson wrong in some important matters. This is a nice display of scientific civility but for those who have been relishing the feud, it isn't much fun.y

JOSEPH KASTNER, author of A Species of Eternity, writes frequently on natural history and is working on a study of American birders, past and present.