Kay Behrensmeyer

Twenty miles east of Laetoli, a volcano known as Sadiman erupted 3.65 million years ago. As the ashes settled to the ground, there was a series of rain showers.

Following one of these showers, a group of hominids walked in the Laetoli area. The ground was still wet and mushy, so they left their footprints behind them. When the sun came out and baked the ashes, these footprints were preserved, as hard as a fossil. Over the years, the winds brought in new sediments, and layers of earth covered many of these footprints. Some, however, were exposed by rains again recently. The first footprints to be found belonged to hares and to birds similar to guinea fowl.

While the KBS controversy was brewing in the mid-1970s, Mary Leakey devoted herself to exploring the Laetoli region. Much of her work at Olduvai had been completed, and she moved to this older site nearby in hopes of finding older stone tools. At the time, the oldest known stone tools were from the Omo, dated at 2.2 million years old. But Mary and her team had found older hominid fossils at the Laetoli sites, and the big question was, did these hominids make tools? As Mary has said, "In archaeology you almost never find what you set out to find."

The way the first footprints were found is as remarkable as it is funny. In September 1976, Mary welcomed a group of friends who had come down to Tanzania for a quick visit. The group included Kay Behrensmeyer, Andrew Hill, a paleontologist who worked for the Nairobi Museum, and Jonah Western [think she means David Western], an ecologist who worked at Kenya's Amboseli National Park. Mary was showing them the sites one day, and as they walked back to camp in the evening. Hill and Western began to toss elephant dung at each other. Elephant dung, when dried, is not offensive at all; it doesn't smell; it's just like a big cake of dried grass. Western buried a big piece at Hill, who ducked and fell on the ground.

Hill noticed some interesting-looking imprints in a flat gray surface. The first little dents he saw were later identified as raindrop prints. But it made him look around, and he found footprints of hares, birds and rhinos. Since then literally tens of thousands of footprints have been found in what became known as Site A, ranging from the tiny tracks left by insects to the massive depressions left by elephants.

Two years later a footprint was found that looked like the mark of a human heel. Excavations began, and it turned outthat the path of footprints went for over 20 yards. It looked as if two different hominids had walked there. Mary Leakey thinks they didn't walk at the same time. The path of one individual was very clear and distinct, while the other set of footprints was blurred and not as sharp. It appeared that they may have been impressed upon two different layers of ash which fell at different times.

Mary Leakey describes the Laetoli footprints as "perhaps the most remarkable finds I have made in my whole career." Because the footprints were so humanlike, she felt they could only have been left by one of our direct ancestors.

What do these footprints tell us about our ancestors? That they walked upright 3.65 million years ago. The shape of the foot is very similar to our own. Because no tools were found in this same level, these hominids must have walked upright before they used tools.

In addition to the footprints, Mary's team found part of a child's skeleton and several fossil remains of adults�two lower jaws, part of an upper jaw and a number of teeth. The best specimen of the lower jaw was called LH 4, for Laetoli Hominid number four. It would become a huge bone of contention.