Strange footprints from Laetoli, Tanzania come from early humans – .

Strange footprints from Laetoli, Tanzania come from early humans – .

Model of Laetoli site A using photogrammetry showing five hominid fingerprints (a); and the corresponding contour map of the Laetoli site in Tanzania generated from a 3D surface scan (b); map showing Laetoli, which is located in the Ngorongoro Conservation Area in northern Tanzania, south of Olduvai Gorge (c); topographic maps of footprint A2 (d) and footprint A3 (e). Credit: Images (a) and (b) by Austin C. Hill and Catherine Miller. Image (c): Illustration using GoogleMaps by Ellison McNutt. Images (d) and (e) by Stephen Gaughan and James Adams

The results provide conclusive evidence that several hominid species coexisted in the landscape.

The oldest unequivocal evidence of standing walking in the human lineage are the footprints discovered in Laetoli, Tanzania in 1978 by paleontologist Mary Leakey and her team. The bipedal pathways date back to 3.7 million years ago. Another series of mysterious footprints was partially excavated at nearby Site A in 1976, but rejected as possibly having been made by a bear. A recent re-excavation of the footprints from Site A in Laetoli and a detailed comparative analysis reveals that the footprints were made by a primitive human, a bipedal hominid, according to a new study published in Nature.

“Given the growing evidence for locomotor and species diversity in the hominid fossil record over the past 30 years, these unusual footprints deserved another look,” says lead author Ellison McNutt, assistant teaching professor at the Heritage College of Osteopathic Medicine at Ohio University. . She began her work as a graduate student in Ecology, Evolution, Environment and Society at Dartmouth College, where she focused on the biomechanics of walking in early humans and used comparative anatomy, including that bears, to understand how the heel bone contacts the ground (a position of the foot called “plantigradie”).

Image of the Laetoli A3 footprint (left) and image of a cast of the Laetoli G1 footprint (right). The analysis shows similarities in the length of the Laetoli A3 and G footprints, but differences in the width of the forefoot, the former being wider. Credit: Image left by Jeremy DeSilva and right by Eli Burakian / Dartmouth

McNutt was fascinated by the bipedal (standing) footprints at Site A in Laetoli. Laetoli is famous for its impressive trail of hominid footprints at sites G and S, which are generally accepted as Australopithèque afarensis—The species of the famous partial skeleton “Lucy”. But because the footprints at Site A were so different, some researchers thought they were made by a young bear walking upright on its hind legs.

To determine the creator of the Site A footprints, in June 2019, an international research team led by co-author Charles Musiba, associate professor of anthropology at the University of Colorado at Denver, traveled to Laetoli, where they searched again and thoroughly cleaned up on the fifth, consecutive footprints. They identified evidence that the fossil prints were made by a hominid, including a large heel and big toe print. The prints were measured, photographed and scanned in 3D.

The researchers compared the traces from Laetoli site A to black bear tracks (american bear), chimpanzees (Pan troglodytes), and humans (a wise man).

Left: Ellison McNutt collects data on a young female black bear (Ursus americanus), who walks bipedally, unaided, through the mud trail at the Kilham Bear Center in Lyme, New Hampshire. Right: Left footprint of one of the young male black bears. Credit: Image at left by Jeremy DeSilva. Image right by Ellison McNutt

They teamed up with co-authors Ben and Phoebe Kilham, who run the Kilham Bear Center, a black bear rescue and rehabilitation center in Lyme, New Hampshire. They identified four semi-wild juvenile black bears in the center, with paws similar in size to the footprints at Site A. Each bear was lured with maple syrup or applesauce, to stand up and walk on his two hind legs on a mud-filled track to capture his footprints.

Over 50 hours of wild black bear video was also obtained. The bears walked two feet for less than 1% of the total viewing time, making it unlikely that a bear made the footprints in Laetoli, especially since no footprints were found from this individual walking on all fours.

When bears walk, they take very wide strides, rocking back and forth, ”says senior author Jeremy DeSilva, associate professor of anthropology at Dartmouth. “They are unable to walk with a gait similar to that of the Site A footprints, because their hip musculature and the shape of their knees do not allow that kind of movement and balance. Bears’ heels narrow and their toes and feet resemble fans, while the earliest human feet are square and have a prominent big toe, the researchers say. Oddly, however, the site A footprints record a hominin crossing one leg over the other as it walks – a gait known as a “crossed step.”

“Although humans generally don’t cross step, this movement can occur when trying to restore balance,” McNutt explains. “Site A footprints may have been the result of a hominid walking over an area that was an uneven surface. “

Ellison McNutt collects data from a young female black bear (Ursus americanus), who walks bipedally, unaided, through the mud trail at the Kilham Bear Center in Lyme, New Hampshire. Credit: Video by Jeremy DeSilva

Based on footprints collected from semi-wild chimpanzees at the Ngamba Island Chimpanzee Sanctuary in Uganda and two captive juveniles at Stony Brook University, the team discovered that chimpanzees have heels relatively narrow compared to their forefoot, a feature common to bears. But Laetoli’s footprints, including those at Site A, have heels wide compared to their forefoot.

The prints from Site A also contained the prints of a large hallux (big toe) and a second smaller digit. The size difference between the two digits was similar to that of humans and chimpanzees, but not black bears. These details further demonstrate that the footprints were likely made by a hominid traveling on two legs. But by comparing the Laetoli footprints at site A and the inferred foot proportions, morphology and probable gait, the results reveal that the footprints at site A are distinct from those at Australopithèque afarensis on sites G and S.

“Thanks to this research, we now have conclusive evidence from the Site A footprints that there were different species of hominids walking bipedally in this landscape but in different ways on different feet,” says DeSilva, who focuses on the origins and evolution of human walking. “We’ve had this evidence since the 1970s. It only took the rediscovery of these wonderful footprints and more detailed analysis to get us here.

Reference: “Footprint evidence of locomotor diversity of early hominids at Laetoli, Tanzania” by Ellison J. McNutt, Kevin G. Hatala, Catherine Miller, James Adams, Jesse Casana, Andrew S. Deane, Nathaniel J. Dominy, Kallisti Fabian, Luke D Fannin, Stephen Gaughan, Simone V. Gill, Josephat Gurtu, Ellie Gustafson, Austin C. Hill, Camille Johnson, Said Kallindo, Benjamin Kilham, Phoebe Kilham, Elizabeth Kim, Cynthia Liutkus-Pierce, Blaine Maley, Anjali Prabhat, John Reader, Shirley Rubin, Nathan E. Thompson, Rebeca Thornburg, Erin Marie Williams-Hatala, Brian Zimmer, Charles M. Musiba and Jeremy M. DeSilva, December 1, 2021, Nature.
DOI: 10.1038 / s41586-021-04187-7

The other co-authors are: Catherine Miller, James Adams, Jesse Casana, Nathaniel Dominy, Luke Fannin, Stephen Gaughan, Austin C. Hill and alumni Camille Johnson ’19 and Anjali Prabhat ’20 in Dartmouth; Kevin G. Hatala and Erin Marie Williams-Hatala at Chatham University; Andrew S. Deane at Indiana University School of Medicine; Kallisti Fabian, Josephat Gurtu and Said Kallindo at the Ngorongoro Conservation Area Authority; Ellie Gustafson and Rebeca Thornburg at the University of Colorado at Denver; Simone V. Gill at Boston University; Elizabeth Kim at the University of Southern California; Cynthia Liutkus-Pierce and Brian Zimmer at Appalachian State University; Blaine Maley of the College of Osteopathic Medicine of Idaho; John Reader at University College London; Shirley Rubin at Napa Valley College; and Nathan Thompson of NYIT College of Osteopathic Medicine.


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