Mary Leakey waits for my next question, watching from behind a thin curtain of cigar smoke. Leakey is as famous for her precision, her love of strong tobacco--half coronas, preferably Dutch--and her short answers as she is for some of the most significant archaeological and anthropological finds of this century. The latter would have hardly been excavated without her exactitude and toughness. And in a profession scarred by battles of interpretation and of ego, Leakey's unwillingness to speculate about theories of human evolution is unique.

These characteristics have given Leakey a formidable reputation among journalists and some of her colleagues. So have her pets. In her autobiography, Disclosing the Past, Leakey mentions a favorite dog who tended to chomp people whom the archaeologist didn't like, "even if I have given no outward sign." So as we talk in her home outside Nairobi, I sit on the edge of a faded sofa, smiling exuberantly at her two dalmatians, Jenny and Sam, waiting for one of them to bite me. I quickly note details--her father's paintings on the wall, the array of silver trophies from dog shows and a lampshade with cave painting figures on it--in case I have to leave suddenly. But the two dogs and soon a cat and later a puppy sleep or play, and Leakey's answers, while consistently private, seem less terse than simply thoughtful.

Leakey first came to Kenya and Tanzania in 1935 with her husband, the paleontologist Louis Leakey, and except for forays to Europe and the U.S., she has been there ever since. During those many years, she introduced modern archaeological techniques to African fieldwork, using them to unearth stone tools and fossil remains of early humans that have recast the way we view our origins. Her discoveries made the early ape Proconsul, Olduvai Gorge, the skull of Zinjanthropus and the footprints of Laetoli, if not household names, at least terms familiar to many.

Leakey was born in England, raised in large part in France and appears to have been independent, exacting and abhorrent of tradition from her very beginnings. Her father, an artist, took his daughter to see the beautiful cave paintings at such sites as Fond de Gaume and La Mouthe and to view some of the stone and bone tools being studied by French prehistorians. As she has written, these works of art predisposed Leakey toward digging, drawing and early history: "For me it was the sheer instinctive joy of collecting, or indeed one could say treasure hunting: it seemed that this whole area abounded in obje cts of beauty and great intrinsic interest that could be taken from the ground."

These leanings ultimately induced Leakey at the age of about 17 to begin working on archaeological expeditions in the U.K. She also attended lectures on archaeology, prehistory and geology at the London Museum and at University College London. Leakey says she never had the patience for formal education and never attended university; she never attended her governesses either. (At the same time, she is delighted with her many honorary degrees: "Well, I have worked for them by digging in the sun.")

A dinner party following a lecture one evening led her, in turn, to Louis Leakey. In 1934 the renowned researcher asked Mary, already recognized for her artistic talents, to do the illustrations for a book. The two were soon off to East Africa. They made an extraordinary team. "The thing about my mother is that she is very low profile and very hard working," notes Richard E. Leakey, former director of the Kenya Wildlife Service, an iconoclast known for his efforts to ban ivory trading and a distinguished paleontologist. "Her commitment to detail and perfection made my father's career. He would not have been famous without her. She was much more organized and structured and much more of a technician. He was much more excitable, a magician."

What the master and the magician found in their years of brushing away the past did not come easily. From 1935 until 1959 the two worked at various sites throughout Kenya and Tanzania, searching for the elusive remains of early humans. They encountered all kinds of obstacles, including harsh conditions in the bush and sparse funding. Success too was sparse--until 1948. In that year Mary found the first perfectly preserved skull and facial bones of a hominoid, Proconsul, which was about 16 million years old. This tiny Miocene ape, found on Rusinga Island in Lake Victoria, provided anthropologists with their first cranium from what was thought to be the missing link--a tree-dwelling monkey boasting a bigger brain than its contemporaries.