By Shaun Smillie

They died suddenly in an Ethiopian riverbed - killed by a single catastrophic event that claimed babies, and possibly their mothers and fathers.

It is a 3,2-million-year-old mystery that scientists have been trying to solve for three decades, and now the man who found the most famous fossil in the world hopes that a South African academic might solve the riddle.

Professor Donald Johanson found Lucy in 1974, but soon after his big find, he discovered in an area just 3km away the bones of between 13 and 17 hominids - including children that were only three or four years old.

And he believes that if it wasn't for Lucy and her catchy name, which was borrowed from the title of The Beatles song Lucy in the Sky with Diamonds, these fossils would have been more famous and recognised by the public.

"What you have here is a snapshot. They probably knew each other, and that is intriguing. The babies in the group probably belonged to the females. They died a sudden catastrophic death," explained Johanson.

The bones belonged to the same species as Lucy, Australopithecus afarensis, and were found near Hadar in Ethiopia.

They were given the name the First Family, and what they give to science is a glimpse of how our earliest ancestors lived with information on social structures, sexual dimorphism and size differences within a single species.

Johanson is currently in South Africa as a guest of the Palaeontological Scientific Trust, an organisation that promotes and funds palaeontology.

He is here to give a series of lectures, but he is also hoping to meet his friend, palaeontologist Dr Bob Brain. He hopes that Brain, with his expertise in taxonomy and the work he has done studying prehistoric predator lairs, will be able to finally solve the mystery.

"I would like him to come to Ethiopia to look at the collection. Bob's training and his eye will bring a different perspective," said Johanson.

Over the years, theories have been put forward as to what killed the group.

The most popular is that they were crossing or resting in a dry riverbed and were surprised by a flash flood. The quality of the fossils, including intricate foot bones, suggests the bodies were covered quickly by water and sediment. Only hominid bones were found, adding to the mystery.

But this theory lost some ground in 2000 when a geologist suggested that materials usually washed down by a sudden flood were absent.

"They might have died of food poisoning, but considering that they were vegetarian, this is unlikely," said Johanson.

Other scientists have suggested that the First Family might have been killed by predators, and their bones then collected in that particular part of the river.

This would dispel the sudden-death theory.

But there are no apparent tooth marks on the bones, although Johanson pointed out that big cats are known to strip flesh from carcasses without leaving telltale chew marks.

And some academics believe there are tooth marks on some of the bones. Nothing is definitive.

The First Family have for long been overshadowed by their fellow afarensis, Lucy.

She is famous because she was an almost complete skeleton, which provided insight into how she moved.

Lucy walked upright, as humans do. She is a household name.

"In the US you can be at a dinner party, and people won't know about a find, but if you mention that it is older than Lucy, then you will get the response 'Older than Lucy. My gosh!'," said Johanson.

With the advent of new technologies and possibly Brain's fresh eyes, Johanson hopes that Lucy's kin, the First Family, might get the public recognition they deserve.