Born on October 14 1925, Tobias died in Johannesburg on Thursday morning after a three-month illness, said Gauteng Tourism Authority spokesman Anthony Paton.

Tobias, who was nominated for a Nobel prize three times, decided to study medicine after his sister, Val, who was 21, died of diabetes.

He asked the family doctor why his sister and his mother's mother had the disease, but he and his mother did not. The reply was that there was no one in South Africa suitably qualified in genetics to answer the question.

Tobias enrolled at the University of the Witwatersrand's Medical School in 1944, later branching into genetics.

"I decided I'd be the first one [to answer this boyhood question] . and I was," he said in 1996.

He later wrote an acclaimed thesis on genetics.

Anger at his sister's death might have begun Tobias's study of humans, but love for humankind led him to spend a lifetime studying its history.

One of his most famous palaeoanthropological finds was Little Foot - four 4.17-million-year-old foot bones unearthed at Sterkfontein by Dr Ron Clarke.

Later, more of the skeleton was unearthed, making Little Foot the oldest, most complete skeleton of a direct ancestor, Tobias explained in 2003, when a new dating technique showed the bones to be considerably older than the first estimate of 3.3-million years.

While Tobias was studying genetics under Professor Raymond Dart - famous for his discovery of what became known as the Taung Skull in 1924 - he "fell under the spell" of palaeoanthropology.

Dart's theory, now accepted, initially shocked scientists across the globe.

The skull is now seen as belonging to a child of the humanoid Australopithecus africanus genus. This was a new species, a link in the chain that ends with modern humankind - Homo sapiens sapiens.

Tobias, who was the only person to hold three professorships simultaneously at Wits, was known for being a friendly, outgoing man, eloquent and able to explain his science to anyone.

In 2002, he hosted his own, popular TV series, Tobias's Bodies.

The series, presented and narrated by himself, consisted of six standalone episodes exploring genetics, anatomy and primatology.

Tobias always had a love for the Sterkfontein Caves, near Krugersdorp on the West Rand, where he led a team of researchers.

He took part in almost all the other major digs in Southern Africa since 1945.

He also successfully campaigned for the Sterkfontein Caves to be proclaimed a World Heritage site.

Tobias was appointed demonstrator in histology and instructor in physiology at the University of the Witwatersrand in 1945. He received his BSc degrees in histology and physiology in 1946-1947, graduated in medicine (MB BCh) in 1950 and received his PhD in 1953.

In 1967, he was awarded a doctorate in science for his published work on hominid evolution.

He established the Institute for the Study of Man in Africa in 1956 to advance the study of human ancestry. In 1959 he became professor and head of the Department of Anatomy, a position he held until 1993, after which he became professor emeritus and head of the research department at the Sterkfontein Caves.

Tobias was appointed honorary professor of palaeoanthropology at the Bernard Price Institute for Palaeontological Research in 1977 and honorary professor in zoology in 1981.

Tobias was the recipient of many awards and honours, including honorary degrees from the universities of Pennsylvania, Cambridge, California, Natal, Cape Town, Unisa, Durban-Westville, Western Ontario, Alta, Guelph and the Witwatersrand.