They are fossils captured in volcanic rock that can be given an absolute date. Any remnant of the past, not just bones, can be considered a fossil. A light rain then turned the ash into a sort of cement that recorded thousands of tracks of antelopes, rhinos, guinea fowl, and monkeys, as well as the footprints of our ancestors.
Volcanic rock -- like the trail at Laetoli -- can be dated by a method called potassium-argon dating. Hot, newly erupted lava and ash contain a form of the chemical element potassium called potassium that is radioactive. Over time, potassium changes, or decays, into a different material, called argon By comparing the ratio of potassium to argon, scientists gauge how long this natural clock has been ticking.
The age of volcanic rock and ash can be "pinpointed" to within roughly twenty thousand years -- a mere moment in Earth's 4-billion-year history. The footprints themselves were an unlikely discovery because they closely resemble modern human footprints, despite being almost 4 million years old. It is noted that the toe pattern is much the same as the human foot, which is much different than the feet of chimpanzees and other non-bipedal beings.
The footprint impression has been interpreted as the same as the modern human stride, with the heel striking first and then a weight transfer to the ball of the foot before pushing off the toes.
Scientists currently don't have a technique for dating fossils like Lucy directly, but they The Laetoli footprints are rare treasures in the record of human ancestry. Two dating techniques were used to arrive at the it is the ancient Laetolil Beds that contain the footprints trackway.
Based on stratigraphic analysis, the findings also provide insight into the climate at the time of the making of the footprints. Pliocene sediments show that the environment was more moist and productive than now. This could have initiated the evolution to bipedalism of the hominins found at Laetoli.
In , after the Laetoli footprints were recorded, they were re-buried as a then-novel way of preservation. The site was re-vegetated by acacia trees, which later gave rise to fears over root growth. In mid, a GCI-Tanzanian team investigated this by opening a three-by-three meter trench, which showed that roots had damaged the footprints. However, the part of the trackway unaffected by root growth showed exceptional preservation.
The success of the experiment led to an increased practice in reburials for preserving excavated sites. In , measures were taken to prevent erosion. The original trackway was remolded and new casts were made. As the trackway is very fragile, the new replica cast was used to guide re-excavation in the field.
A team of specialists, one being Fiona Marshall , re-excavated half of the trackway to record its condition, stabilize the surface, extract dead roots and rebury it with synthetic geotextile materials. This allows the trackway surface to breathe, and protects it against root growth. Proposals for lifting the track and moving it to an enclosed site have been suggested, but the cost is viewed as outweighing the benefits: Thus, burial seems to be the most effective method of preservation.
From Wikipedia, the free encyclopedia. Life timeline and Nature timeline. Paleontology and Geology of Laetoli: Human Evolution in Context: Fossil Hominins and the Associated Fauna. Paleontology and Geology of Laetoli, Tanzania: Geology, Geochronology, Paleoecology and Paleoenvironment. The Laetoli Footprint Trail: Archived from the original on 17 July Randall Haas, Jr Explicit use of et al. Scientists tend to believe that these footprints could not have come from modern man, so it must suggest that hominids have been walking on two feet longer than previously thought.
Mary Leakey was on an expedition in Tanzania with a group of other scientists when he found the Laetoli footprints. They were there to study ancient remains, but they found something equally, if not more, interesting.
The group was walking toward Olduvai Gorge together one day during their expedition. Two of the paleoanthropologists began throwing elephant dung at one another and otherwise goofing off. During the action, the Laetoli footprints were literally stumbled upon. The Laetoli footprints consist of two tracks of about 30 meters. One of the sets of prints is significantly larger than the other.
This suggests that there were at least two hominids walking in Laetoli when the prints were made. The tracks were made by either a woman and a man or an adult and a child. There could also be a third set of tracks within the larger set.
It looks as if a third hominid, that walked along behind the first two, had stepped in the larger tracks. Leakey made plaster casts of the tracks and then covered them. She marked the location so they could go back.
The fossils were dated at roughly 3. Most scientists agree that the Laetoli footprints must have come from a hominid species that walked bipedally, as it is obvious that the owners of these prints walked on two legs.