Over the past decade, new discoveries of ancient human and pre-human fossils in Africa are forcing paleontologists and anthropologists to re-examine the history of the human species. Many of these important fossil discoveries have occured and are still occurring on the banks of Lake Turkana in Kenya, where a large team of workers at the Koobi Fora camp is making discoveries which trace human evolution back two and three million years. The head of the highly successful and productive Koobi Fora project is Richard E. Leakey, son of the world-famous prehistorians Louis and Mary Leakey. In light of the Koobi Fora project's success, Leakey has decided to present his findings to the rest of the world in the form of easy-to-read, fairly short books.

The People of the Lake: Mankind and Its Beginnings (Leakey's second and latest book), which focuses on the Koobi Fora finds, is a credit to Leakey. Leakey and co-author Roger Lewin write intelligent, provocative prose and present their amazing discoveries to readers with just the right combination of lucidity and academic integrity.

To prevent his book from becoming an endless series of dated skulls and cranium sizes, Leakey goes beyond the cell of paleontology. He uses his fossil discoveries to speculate about the nature of ancestral societies. Leakey pieces together his chips and bones and then tries to pinpoint social and economic attributes of the hunter-gatherer bands that once inhabited the earth.

This is difficult business. The fossils presently available barely tell us what our progenitors looked like, much less the socio-economics of the nomadic hordes in which they allegedly roamed. But Leakey is intelligent and conscientious, and he treads carefully where the footing is not firm, taking pains to warn the reader when he lacks evidence to substantiate his conclusions. Moreover, Leakey seems to have absorbed every tiny fact ever written pertaining to his field and, consequently, his contentions come across as carefully considered and tenable. It is the breadth of Leakey's knowledge in the field and the skilled writing that makes his conjectural synthesis work.

The first few chapters are the least controversial, but are readable and illuminating nevertheless. Essentially, Leakey traces the history of paleontology and what it has been able to tell us about our ancestors. But along the way, Leakey adds his new theories based on the Koobi Fora discoveries. What results is, in fact, a reinterpretation that alters the earlier hypothetical outline of man's evolution conceived before African discoveries at Koobi Fora and other sites. The basic hypothesis which Leakey then transforms claims that man's evolution involved a gradual transformation from simian, to Ramipithecus, to Australopithecus, and then finally, perhaps only 50,000 years ago, to modern man. However, Leakey contends in The People of the Lake that Australopithecus was a cousin of man, but not an ancestor.

According to Leakey, the Australopithecus branch and the evolutionary branch leading to man diverged several milion years ago, with the Australopithecus dying out, leaving man without phylogenetic cousins. Leakey replaces the older theory by offering another line of descent: from Ramipithecus to Homo habilis to Homo erectus to Homo sapiens. This revision is significant because it creates the puzzle of the extinction of our Australopithecus cousins, and pushes back the time of man's origin much further than previously imagined, to perhaps 500.000 years.

Throughout the earlier chapters, Leakey breaks the somewhat monotonous account of paleontological history with amusing anecdotes. He tells about his friend almost being gobbled up by a crocodile while swimming in Lake Turkanay be offers insights into the personalities of big-time anthropologists and paleontologists and draws the reader into the world of bones and fractured skulls until the reader begins to share his enthusiasm.

Leakey devotes a large portion of The People of the Lake to explaining why the line of hominids leading to the evolution of man survived while the Australopithecene line died out. He argues that at some point our hominid line developed a complex economic system of gathering and hunting that required cooperation between individuals in a clan. This cooperative system, besides being intrinsically more productive, engendered the evolution of a special intellectual capability on the part of our pre-historic ancestors. The brains of our ancestors became increasingly subtle and complex because cooperation in a society requires that its members be able to interact with each other, empathize with fellow clan members, and take on specialized roles.

Leakey argues that this greater degree of " intelligence," along with the inherent efficiency of cooperative societies, may have allowed the hominid line to survive while our last cousins perished. Leakey develops this argument carefully and logically so that when he holds it up to the competing theory that our ancestors survived because they were more aggressive and domineering, his view makes more sense.

Leakey extends this argument to make his own claims about the nature of intelligence and language. He says we can no longer define man's uniqueness by either his ability to construct sentences or his ability to construct sentences or his ability to make tools. He cites the recently discovered ability in chimpanzees and gorillas to make and use primative tools as well as to create basic sentences. The progress chimpanzees and gorillas have made in the realm of language is particularly revolutionary and calls for a reevaluation of the fundamental differences between man and animal, Leakey writes.

Through the use of sign language and push-button computers, apes have shown they can use symbols to generalize, pose questions and express moods. These experiments contest the claims made by thinkers from Descartes to Noam Chomsky that man's uniqueness can be found in his unusual ability to think and talk in abstract terms. What is it, then, Leakey asks the reader, that makes man different? What special quality does the human brain possess?

The answer, again, lies in the peculiar nature of man as the only primate with a complex, cooperative society, according the leakey. Intelligence and language represent man's adaptation to living in such cooperative societies.

Leakey saves his final chapter, entitled "An End to the Hunting Hypothesis," for a severe critique of those who see innately aggresive tendencies in man. Leakey focuses his argument to refute the likes of American anthropologist Marshall Sahlins, Nobel prize-winner Konrad Lorenz, Raymond Dart--discoverer of the first Australopithecene. Robert Audrey--author of The Territorial Imperative and The Hunting Hypothesis, Desmond Morris--author of the Naked Ape and other who try to portray ancient man as the vicious truncheon-toting caveman caricatured in comic strips. Leakey contends that such aggressive people could never have survived--they would have killed themselves off. To the contrary, man has succeeded precisely because he has learned to cope with his fellow man.