Model of Laetoli Site An utilizing photogrammetry revealing 5 hominin footprints (a); and corresponding contour map of the site at Laetoli, Tanzania, created from a 3D surface scan (b); map revealing Laetoli, which is situated within the Ngorongoro Conservation Area in northern Tanzania, south of Olduvai Gorge (c); topographical maps of A2 footprint (d) and A3 footprint (e). Image (c): Illustration using GoogleMaps by Ellison McNutt.
Findings supply definitive proof that several species of hominins co-existed on the landscape.
Another set of strange footprints was partially excavated at close-by Site A in 1976 but dismissed as possibly being made by a bear. A recent re-excavation of the Site A footprints at Laetoli and a comprehensive relative analysis reveal that the footprints were made by an early human– a bipedal hominin, according to a new research study reported in Nature.
” Given the increasing proof for locomotor and species diversity in the hominin fossil record over the past 30 years, these uncommon prints deserved another look,” states lead author Ellison McNutt, an assistant teacher of direction at the Heritage College of Osteopathic Medicine at Ohio University. She began the work as a graduate student in Ecology, Evolution, Environment, and Society at Dartmouth College, where she concentrated on the biomechanics of walking in early people and made use of comparative anatomy, including that of bears, to understand how the heel bone contacts the ground (a foot position called “plantigrady”).
Image of Laetoli A3 footprint (on left) and image of a cast of Laetoli G1 footprint (on right). Analysis reveals similarities in length of Laetoli A3 and G footprints however differences in forefoot width with the previous being wider. Credit: Image on left by Jeremy DeSilva and on right by Eli Burakian/Dartmouth
McNutt was captivated by the bipedal (upright walking) footprints at Laetoli Site A. Laetoli is well-known for its excellent trackway of hominin footprints at Sites G and S, which are generally accepted as Australopithecus afarensis– the types of the popular partial skeleton “Lucy.” However because the footprints at Site A were so various, some scientists believed they were made by a young bear strolling upright on its hind legs.
To identify the maker of the Site A footprints, in June 2019, a worldwide research study team led by co-author Charles Musiba, an associate professor of anthropology at University of Colorado Denver, went to Laetoli, where they re-excavated and completely cleaned up the five, consecutive footprints. They identified evidence that the fossil footprints were made by a hominin– including a large impression for the heel and the huge toe. The footprints were determined, photographed and 3D-scanned.
The scientists compared the Laetoli Site A tracks to the footprints of black bears (Ursus americanus), chimpanzees (Pan troglodytes), and humans (Homo sapiens).
On left: Ellison McNutt collects data from a juvenile female black bear (Ursus americanus), who strolls bipedally, unassisted through the mud trackway at Kilham Bear Center in Lyme, New Hampshire. On right: Left footprint from among the juvenile male black bears. Credit: Image on left by Jeremy DeSilva. Image on right by Ellison McNutt
They teamed up with co-authors Ben and Phoebe Kilham, who run the Kilham Bear Center, a rescue and rehabilitation center for black bears in Lyme, New Hampshire. They identified four semi-wild juvenile black bears at the Center, with feet similar in size to that of the Site A footprints. Each bear was lured with maple syrup or apple sauce, to stand and walk on their 2 hind legs across a trackway filled with mud to record their footprints.
Over 50 hours of video on wild black bears was also obtained. The bears walked on 2 feet less than 1% of the total observation time making it unlikely that a bear made the footprints at Laetoli, especially considered that no footprints were found of this private walking on 4 legs.
As bears stroll, they take extremely large actions, wobbling back and forth,” says senior author Jeremy DeSilva, an associate professor of sociology at Dartmouth. Curiously, though, the Site A footprints tape a hominin crossing one leg over the other as it strolled– a gait called “cross-stepping.”.
” Although people do not normally cross-step, this movement can take place when one is trying to reestablish their balance,” says McNutt. “The Site A footprints may have been the result of a hominin strolling throughout an area that was an unlevel surface area.”.
Ellison McNutt gathers data from a juvenile female black bear (Ursus americanus), who walks bipedally, unassisted through the mud trackway at Kilham Bear Center in Lyme, New Hampshire. Credit: Video by Jeremy DeSilva.
Based on footprints gathered from semi-wild chimpanzees at Ngamba Island Chimpanzee Sanctuary in Uganda and 2 captive juveniles at Stony Brook University, the group discovered that chimpanzees have relatively narrow heels compared to their forefoot, a quality shared in common with bears. The Laetoli footprints, consisting of those at Site A, have broad heels relative to their forefoot.
The Site A footprints also contained the impressions of a large hallux (big toe) and smaller 2nd digit. These details even more demonstrate that the footprints were most likely made by a hominin moving on 2 legs. In comparing the Laetoli footprints at Site A and the presumed foot percentages, morphology, and likely gait, the results expose that the Site A footprints are unique from those of Australopithecus afarensis at Sites G and S.
” Through this research, we now have conclusive evidence proof the Site A footprints that there were different hominin species types bipedally on this landscape but however different various methods different feet,” says DeSilva, who focuses on the origins and evolution development human walking.
Reference: “Footprint evidence of early hominin locomotor variety 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, 1 December 2021, Nature.DOI: 10.1038/ s41586-021-04187-7.
The other co-authors include: Catherine Miller, James Adams, Jesse Casana, Nathaniel Dominy, Luke Fannin, Stephen Gaughan, Austin C. Hill, and alumni Camille Johnson 19 and Anjali Prabhat 20 at 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 University of Colorado 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 at Idaho College of Osteopathic Medicine; John Reader at University College London; Shirley Rubin at Napa Valley College; and Nathan Thompson at NYIT College of Osteopathic Medicine.
Design of Laetoli Site An using photogrammetry showing 5 hominin footprints (a); and matching contour map of the website at Laetoli, Tanzania, produced from a 3D surface area scan (b); map showing Laetoli, which is located within the Ngorongoro Conservation Area in northern Tanzania, south of Olduvai Gorge (c); topographical maps of A2 footprint (d) and A3 footprint (e). A current re-excavation of the Site A footprints at Laetoli and a detailed relative analysis expose that the footprints were made by an early human– a bipedal hominin, according to a brand-new study reported in Nature.
Image of Laetoli A3 footprint (on left) and image of a cast of Laetoli G1 footprint (on right). To figure out the maker of the Site A footprints, in June 2019, an international research team led by co-author Charles Musiba, an associate teacher of sociology at University of Colorado Denver, went to Laetoli, where they re-excavated and completely cleaned the 5, successive footprints. In comparing the Laetoli footprints at Site A and the presumed foot proportions, morphology, and likely gait, the results expose that the Site A footprints are unique from those of Australopithecus afarensis at Sites G and S.
” Through this researchResearch study we now have conclusive definitive proof the Site A footprints that there were different hominin species walking strolling on this landscape but however different various methods different feet,” says DeSilva, who focuses on the origins and evolution development human walking.