Laetoli << lay TOH lee >> fossil site is a location in northern Tanzania where important fossils and other evidence of early prehuman ancestors have been discovered. In the 1970’s, a team of anthropologists led by the British archaeologist and anthropologist Mary Leakey excavated fossils of a prehuman creature later identified as Australopithecus afarensis. In 1978, anthropologists uncovered fossilized footprints in a layer of volcanic ash. The footprints, which are about 3,600,000 years old, are among the oldest evidence for bipedal locomotion (upright walking on two legs) by a humanlike creature. Scientists consider bipedal locomotion a feature unique to the hominins. In scientific classification, hominins make up the group that consists of human beings and early humanlike ancestors.
The fossil footprints were preserved at the Laetoli site by a fortunate sequence of events. About 3,600,000 years ago, a volcano, now called Sadiman, erupted near the site and deposited a layer of ash across the landscape. A light rain fell sometime after the eruption and dampened the ash. Many animals, including hominins, walked across the wet ash, leaving footprints in the soft material. The sun dried the ash into cementlike hardness within a short time. Soon, Sadiman erupted again and deposited a fresh layer of ash that covered and preserved the footprints. Millions of years later, erosion exposed the footprints.
The hominin footprints create a trail about 80 feet (24 meters) long. Hominins made at least two tracks. Anthropologists believe that Australopithecus afarensis individuals, possibly walking together, made the tracks. Scientific studies of the footprints have determined that they show a pattern of upright walking similar to that of modern human beings. At the time of their discovery, the Laetoli footprints represented the oldest evidence for upright walking ever found. Since the 1970’s, however, anthropologists have found other fossil remains that indicate prehuman ancestors probably walked bipedally as early as 6 million years ago.
In 1979, Leakey and her team covered the site with sand and boulders to protect the footprints. However, scientists became worried as some of the Laetoli footprints were damaged or destroyed by erosion, plant growth, and even vandalism. In the 1990’s, scientists re-excavated the site and removed vegetation that threatened the footprints. They took detailed photographs and measurements of the footprints and the surrounding area using technologies that were unavailable to Leakey’s team in the 1970’s. The scientists then covered the site with a protective layer of earth and other materials to preserve the footprints and protect them from plant growth and erosion.
See also Australopithecus; Prehistoric people (The australopithecines).
