In 1978, several footprints were unearthed in Laetoli, in northern Tanzania. Printed on a volcanic ash layer 3.66 million years ago by a group of Australopithecus Afarensis-the species to which Lucy belonged - suppose the oldest testimony of bipedism in the hominidae family. In addition to this valuable finding, among the many remains explored in the African deposit, another set of footprints caught the attention of the researchers and raised a certain debate: five consecutive footsteps that some identified as belonging to another type of hominid; However, certain affinities with bearshots prevented from being conclusively identified. That second group would fall into oblivion in later years.
We had to wait until 2019 for a new team of scientists to reexamine that part of the laetoli deposit. They created a digital file using 3D photogrammetry and laser scanning and compared the five footprints with other bears, chimpanzees and modern humans. "Given the growing scientific evidence in the last 30 years on locomotive diversity and species in the fossil record of hominids, these unusual footprints deserved another look," explains Ellison McNutt Teacher in Heritage College of Osteopathic Medicine from Ohio University and Principal author of an article that is published on Wednesday in Nature.
The set of new analysis reveals that the traces were left by a kind of hominid still unknown. "The scarce width of its footsteps corroborates the original interpretation that it was a small hominid bipede of cross steps," write the authors. A detail that has drawn attention and that it is difficult to interpret: the foot crosses ahead of the body to touch the ground right in front of the other foot. "Although humans do not usually walk with the cross pass, that movement can occur when one tries to recover balance," McNutt nuances. "The traces could have been the result of an individual walking on an uneven surface."
In any case, "the inferred proportions of the feet, the parameters of the march and the 3D morphologies of the fingerprints of the deposit to [in which the five footprints were found] are easily distinguished from those of the yacing G [where the Of the Australopithecus], which indicates that in Laetoli there were two taxons of hominids with different feet and running at least two tampons, "the researchers conclude in the Nature article.
The team also points out that, although thousands of animal fossils have been found in Laetoli, none corresponds to bears. The team collaborated with a rescue and rehabilitation center of black bears (Nersus Americanus), where they selected four semisalvage specimens with legs similar to that of the traces of Laetoli. They made molds and recorded more than 50 hours of video, in which they found that the bears walk on two legs less than 1% of the time, which makes it very unlikely that the traces in Laetoli were left by a bear, Maxime considering that No other traces of bear walking on four legs found.
"When the bears walk on two legs take very spacious steps, staggering back and forth," says Jeremy Desildo, professor of anthropology in Dartmouth and main co-author of the study. "They are unable to walk with a step similar to the traces, since the musculature of their hips and the shape of their knees do not allow that type of movement and balance." The researchers also explain that the heels of the bears narrow and that their fingers are a fan, while the feet of the first humans are square and have a prominent fat finger.
Traces of Semisalvage Chimpanzees (Pan Troglodytes) were also collected in the sanctuary of the island of Ngamba, in Uganda, in addition to those of two young specimens in captivity at Stony Brook University in New York. Researchers explain that chimpanzees have relatively narrow heels compared to the front of the foot, a feature they share with bears. "The hominids of Laetoli walked with a distinctive heel blow and the hallux (fat finger) stood out slightly to one side, although not as much as that of a chimpanzee," he resumes Desilava.
While the analysis set points out that the traces were left by human, the proportions of the feet, morphology and the type of advance show that they are different from those of Australopithecus Afarensis. "The traces can teach us some things about their creators but not all; until we have more fossils in the area we can only speculate on their appearance and behavior," says the researcher. What can be affirmed is that they lived at the same time as the Australopithecus: 3.66 million years ago.
"The traces that we excavate in the Yacimiento A were in the same layer of Toba that the famous footprints of the G site," says Desilava. "Since all occurred in a short period of time in LAETOLI, it is a solid proof that the two species not only coexisted but were contemporary in the same landscape." Thus, according to the researchers, the finding supposes a new test of diversity in the family in this period. "We already had evidence of this since the 1970s, it has only needed the rediscovery of these wonderful traces and a more detailed analysis to get here."
Date Of Update: 07 December 2021, 15:37
