This cry of utter joy and excitement came from the mouth of American palaeontology student Tom Gray, on that morning of Sunday 24 November 1974, in the Ethiopian hills of Hadar.

His colleagues from the International Afar Research Expedition heard it and came running, taking care not to tread on any hominid fossils... and were stunned by the sight that greeted them.

A few years earlier, Maurice Taïeb, a French geologist currently working at the CEREGE laboratory in Aix-en-Provence, had spotted the exceptional potential for fossil discoveries in this region of approximately 80 square kilometres, in northwest Ethiopia, west of the Rift Valley depression. He recalls those early moments:

« In the centre of a rectangle ten metres by two, open to the sky and uncovered by runoff water, dozens of ribs and vertebrae were showing on the surface, packed in together – a foretaste of the almost complete skeleton that would later be reassembled by my American colleague Donald Johanson. It was a very moving sight... unforgettable ».

What happened next has now become legend in human palaeontology. When they returned to their base camp at Sidi Hakoma the researchers, the guides and the workers from the Afar ethnic group celebrated the fantastic discovery.

The champagne flowed in honour of the hominid fossil just exhumed from its patch of earth, and playing on the camp's little tape recorder was the famous Beatles tune, Lucy in the Sky with Diamonds.. A unanimous decision was taken to name the new arrival to the family Lucy – the already sizeable family of distant ancestors to the human race, Homo sapiens.

« The main reason was that it was much easier to pronounce than the scientific name for the genus she belonged to – Australopithecus! », recalls Maurice Taïeb.

So who is this Lucy, who went on to receive unprecedented media attention and for many years occupied the envied position of grandmother of humanity? It was only after complex dating work and analysis of her skeleton in comparison with other hominids known at the time that her age and exact identity were established.

So we had to wait several years to establish her age, until a reliable volcanic marker was discovered just below the sediment where the precious fossil was found. The result: Lucy evolved around 3.2 million years ago. When this date was announced it was as if a bomb had been let off.

François Marchal, a palaeoanthropologist from the Anthropology and Biological and Cultural Adaptability laboratory in Marseille, explains:At the time, Lucy simply belonged to the oldest species in the line of human descent, and it was logical to place her within the genealogical tree of hominids – ie all human forms extinct or living – at the origin of all the others ».

Even more striking was the fact that four years after being discovered, Lucy, thanks to the 52 bone fragments she left behind, and the other fossils dug up in Hadar would give rise to the creation of a new species called Australopithecus (a term designating a group of African bipedal hominids with a brain smaller than 500 cubic centimetres and powerful jaws).

In 1978 Donald Johanson, Tim White and Yves Coppens named this species Australopithecus afarensis.

From the many different studies conducted over the last 30 years, the body structure and environment of the afarensis are now well known.

Lucy, a female approximately 20 years old, and barely one metre tall, belonged to a species that evolved over several hundred thousand years in eastern Africa, from present-day Ethiopia to Tanzania, via Kenya. The afarensis had an average cranial capacity of around 400 cubic centimetres – the smallest of all known hominids. They show numerous characteristics similar to our own: for example, their hands were certainly capable of making a very precise grip.

They developed a form of bipedalism, but the afarensis must have used it interchangeably with tree climbing. This form of bipedalism must have been certainly very different from our own: much more ambling with wide swings from side to side. This gait must have presented these hominids with certain problems, because it expended a great deal of energy – a good reason to continue climbing trees.

Over the course of their history, the afarensis evolved in savannah landscapes that underwent numerous changes over the geological eras, alternately becoming more or less wooded or open, according to the changes in climate.

Was it in order to adapt to these environmental changes that certain Australopitheci gradually favoured bipedalism in their evolutionary strategies, particularly in the east of the Rift Valley? Possibly, but this theory is not unanimously accepted among palaeoanthropologists.

Cautiously wandering around the wooded savannah in search of the roots and tubers they fed on, or even some carrion, Lucy and her relatives ran the constant risk of running into fearsome carnivores, such as the machairodus, a sort of tiger with curved teeth, or a herd of dinotheriums, from the elephant family, who used their lower tusks for breaking up branches. Sometimes, in order to reach a less dangerous or greener area, they had to cross water, and ran the risk of drowning. This is probably how Lucy lost her life, some 3.2 million years ago, as the position of her skeleton and the type of sediment in which she was found seem to indicate.

For many years Lucy was the uncontested star of hominid fossils... but what has she become 30 years after she was discovered? Without wishing to cause her offence, we must admit that since then she has come down off her pedestal.

First of all, she had to make way for several other candidates for the envied title of oldest ancestor in the human line. One of these was Orrorin tugenensis, a 6 million-year-old fossil discovered in Kenya, whose straight femur proves that he walked much more upright than Lucy…

Another claimant to the title was the Ethiopian Ardipithecus kadabba, with 5.7 million years on the clock and a height of over a metre, but whom some researchers believe to be closer to the line of great apes.

As for Toumaï, or Sahelanthropus tchadensis, who was unearthed in Chad in 2001 – he has caused a great deal of controversy, having both prehuman and simian characteristics, and his age of 7 million years...

Worse still for Lucy, the list of her “contemporaries“ – hominids from the same time period – has also got longer. Ranging between 4.2 and 1 million years old, there are nine species divided into three genera, who appear and disappear, from Tanzania to Chad, via Kenya and South Africa.

There are five Australopitheci (anamensis, afarensis, africanus, bahrelghazali and garhi), a genus for which the first fossil evidence was discovered in 1924 in South Africa, and three Paranthropi (aethiopicus, boisei and robustus), sometimes called robust Australopitheci, who are characterised by their robust chewing features and skulls... Kenyanthropus platyops, discovered in 1999, completes the picture.

Also, a majority of palaeoanthropologists now agree that the afarensis are not the most suitable candidates for the title of ancestors of the earliest Homos: Homo habilis and Homo rudolfensis, who appeared in eastern and southern Africa 2.5 million years ago.

Despite all that, this little female exhumed from the hills of Afar still holds a special place in the history of palaeoanthropology.

« Because of the quantity and quality of the remains, since almost 500 remains attributed to afarensis have been discovered in Hadar over the course of various expeditions, this species has become an incomparable study model, offering the opportunity to shed light on issues like variability between individuals, morphological differences between males and females, or locomotion, reveals François Marchal. This work is still ongoing ».

Today, Lucy and her relatives have been laid to rest in a safe in Addis Ababa, the Ethiopian capital, carefully kept away from the public gaze. Scientists have access to them, when their research requires them to work on the originals, rather than the numerous casts in laboratories and museums all over the world. Through their work they are attempting, thanks to Lucy, to penetrate the persistent mystery of our origins, somewhere in East Africa.

Pedro Lima