Footprints in the ashes

About 36,000 centuries ago, hominids walked across rain-soaked volcanic sludge in Tanzania. Peter Fairley traces their steps

THE LAST time I had felt any emotion about footprints was when we discovered some in a flowerbed after our house had been burgled. The detective work had been brief and the enquiries inconclusive. The remarkable thing about the prints I was now studying was that the detective work was still going on after 20 years, and the prints themselves were at least 3.6m years old - or, as our African escort, Luther, preferred, "36,000 centuries".

Luther was a Masai, working as a guide for the Tanzanian Department of Antiquities. "It's a rule of thumb in anthropology," he explained, "that the length of the foot is about 15 per cent of a person's height. We conclude that one of these hominids was about 4ft 8in [1.4m] tall, the other eight inches [122cm] shorter."

Hominids. The last time I'd heard the word (which basically means "family of Man") was 40 years earlier when I had watched the archaeologist Louis Leakey lay out parts of a skull at a press conference in London, declaring: "We have named this hominid Zinjanthropus, or Zinj for short. We believe he is a true ancestor of modern Man." We hacks took one look at the hominid's huge jaw and nicknamed him "Nutcracker Man".

Now I was at Olduvai Gorge in Tanzania, the very place where Nutcracker Man and later hominids had been found. The more I moved around the area, the more I realised one of two things had happened: either fate had chosen this as the place to have some fun, or an incredible set of coincidences had occurred.

Olduvai Gorge is a deep fissure 55km long, wriggling through a volcanic region of Tanzania like a snake with a forked tail. Most of the fossils that tell virtually the whole story of human evolution, from ape to modern man, have been found in the snake's "belly". But the human-like footprints I was interested in - three sets in a 25m-long trail - were found 35km away in a flat area known as Laetoli.

As we sped along the bottom of the hot, dusty gorge, Luther described the latest scientific reconstruction of events at Olduvai and Laetoli. The "coincidences" started between 3.6m and 3.8m years ago and lasted, initially, a month. First, the volcano Sadiman - which still dominates the landscape - started to erupt, belching clouds of ash skywards and turning day into night for miles around. This had not disturbed the animals around Laetoli: giraffes with antlers like reindeer, elephants with downward- curving tusks, white rhino, hyenas, hares, jackals and guineafowl.

Then it started to rain, heavy downpours that turned the freshly deposited ash into a stiff porridge. This captured the animals' tracks in sharp relief. A three-toed horse (hipparion) clip-clopped across the "porridge", followed by its foal. But before Sadiman started belching again, something far more significant happened. Three hominids - probably a male, a female and a child, and certainly some of the earliest of our ancestors to use two legs rather than four - went walkabout.

Our Range Rover jerked to a halt. During the ride, Luther had explained that Laetoli contained a large expanse of pale grey lava, pockmarked with animal tracks, parts of which were still covered by a thick mat of tangled yellow grass. Rectangles had been cut from these, revealing the hominids' steps. What we came across instead was a fenced-off area containing a large expanse of plastic sheeting, covered with river sand and held down with boulders. Not a footprint, animal or hominid, was visible. A museum incorporating the footprints was soon to be built on the site, Luther explained, assuring us that the fibreglass replicas back at Olduvai were "easier to understand" anyway.

Before I got back into the Range Rover, I spent some minutes drinking in the desolation, the silence, and the size of the brooding volcano. Sadiman had continued to puff out ash for centuries, layering some parts of Laetoli to a depth of 7m. I kept asking myself, "Why? Why here?" What had made Louis and Mary Leakey pick that spot - well clear of the gorge and all the other evidence - to dig and uncover the oldest clues yet to Man's origins?

Luther knew the answer. "My tribe, the Masai," he said simply. He went on to explain that, while the Leakeys were scraping and brushing away in the gorge, Masai herdsman told them about a large number of fossils lying out in the open at Laetoli (their name for the red lily that grows there).

To date, fossilised remains of 22 hominids have been found, including two lower jaws, a section of upper jaw, several teeth and part of a child's skeleton, together with fragments of long-extinct animals. But it took another coincidence, in 1975, to expose the footprints.

Two of Mary Leakey's field workers were larking about one evening, pelting each other with elephant dung. One ducked to avoid being hit - and there, in front of his eyes, was a regular pattern of punctures in the lava crust. Closer inspection revealed that they were animal footprints. The hunt switched to prints rather than fossils. A season later, the hominid trail was uncovered.

I decided to return to the visitor centre at Olduvai, to take a second look at the fibreglass casts - but not before we had seen the other archaeological sites in the gorge itself. Here, at different depths in the lava, remnants of four types of early human had been found within a few kilometres of each other. First, Zinj (Nutcracker Man); then Homo habilis (Handy Man); then Homo erectus (Upright Man); and finally Homo sapiens (Modern Man).

At one site, small fragments of fossil were still lying around. Again I was struck by the machinations of fate, not simply in laying down two million years of volcanic deposits in orderly layers - and fossilising whatever creatures were around each time - but also in producing the topography to expose them. Giant earth movements tilted the whole area, creating the gorge and the river to cut through the layers, baring them for archaeologists to study with ease.

Inside the visitor centre, the relationship of the various reconstructed skulls, pieces of skeleton and footprints fell into perspective. Potassium- , argon- and carbon-dating had established the age of each item precisely; Luther showed us pressure marks in some footprints, indicating that the leader had a striding gait; he pointed to one particularly clear print with a raised arch, rounded heel, pronounced "ball" under the foot, and forward-pointing big toe. "Just like yours and mine," he said.

As we drove away, I marvelled again at how the Leakeys had focused on that particular gorge, miles from anywhere, where only sisal plants, aloes and colourful birds now survive. But this time I knew the answer to the question, "Why here?" A notice had explained that, in 1911, a German entomologist, Professor Katt-winkel, had entered the gorge in pursuit of butterflies. He had found a collection of fossilised bones and taken some back to Berlin, where they were identified as the bones of the extinct three-toed horse. Twenty years later, Louis Leakey had seen the bones in Berlin, realised their significance and negotiated "rights" to excavate in the gorge. Within hours, he had started to find stone tools. More coincidences? Or fate? Or perhaps divine guidance? !

TRAVEL NOTES

GETTING THERE: Trailfinders (0171-938 3366) has return flights to Nairobi from London for pounds 406 with Swissair. Campus Travel has flights for students on British Airways for pounds 378.

SAFARIS: United Touring International (0181-905 6525) has set and tailor- made tours in Tan-zania; three nights from pounds 300. Peter Fairley visited Olduvai on a three-night safari costing pounds 396.

The visitor centre is open daily, admission US$2. Guides can be hired at the gorge for about $20.

FURTHER INFORMATION: British passport-holders need a visa for Tanzania; apply to the Tanzania High Commission (0171-499 8951). The Tanzania Tourist Office (0171-407 0566)is at 78-80 Borough High Street, London SE1 1LL.