4 December 2022 The Future is the Product of the Past

Tanzania’s mysterious footprints were made by early humans, not bears

The prehistoric footprints discovered by archaeologists caused confusion because scientists looked at them again to determine whether they were left by humans or extinct animals.

The oldest clear evidence of upright walking in the human lineage is 3.7 million-year-old footprints discovered by paleontologist Mary Leakey and her colleagues in Laetoli, Tanzania, in 1978.

Another set of mysterious footprints was partially excavated at a nearby location, known as site A, in 1976 but dismissed as possibly having been made by a bear.

A recent re-excavation of the site A footprints at Laetoli and comparative analysis reveal that the footprints were made by an early human— a bipedal hominin, according to a new study reported in Nature.

“Given the increasing evidence for locomotor and species diversity in the hominin fossil record over the past 30 years, these unusual prints deserved another look,” says lead author Ellison McNutt, Guarini ’19, who started the work as a graduate student in the Ecology, Evolution, Environment, and Society program, and is now an assistant professor of instruction at the Heritage College of Osteopathic Medicine at Ohio University. At Dartmouth, she focused on the biomechanics of walking in early humans and utilized comparative anatomy, including that of bears.

McNutt was fascinated by the bipedal (upright walking) footprints at site A. Laetoli is famous for its impressive trackway of hominin footprints at sites G and S, which are generally accepted as Australopithecus 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.

Comparing the A3 (photo on left) and G footprints revealed that the A3 and G footprints differ in width. On right is a cast of G1. (Photos by Jeremy DeSilva [left] and Eli Burakian ’00)
Comparing the A3 (photo on left) and G footprints revealed that the A3 and G footprints differ in width. On right is a cast of G1. (Photos by Jeremy DeSilva [left] and Eli Burakian)

To determine the maker of the site A footprints, in June 2019, an international research team led by co-author Charles Musiba, an associate professor of anthropology at the University of Colorado Denver and a Montgomery Fellow, went to Laetoli, where they re-excavated and fully cleaned 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 big toe. The footprints were measured, photographed, and 3D-scanned by Anjali Prabhat ’20; Catherine Miller, Guarini ’23; and Luke Fannin, Guarini ’24, who are co-authors of the paper.

The researchers compared the site A tracks to the footprints of black bears, chimpanzees, and humans. 

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, N.H. 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 applesauce to stand up and walk on its two hind legs across a trackway filled with mud to capture its footprints.

Over 50 hours of video on wild black bears were also obtained. The bears walked on two feet less than 1% of the total observation time, making it unlikely that a bear made the footprints at Laetoli, especially given that no footprints were found of that individual walking on four legs.

“As bears walk, they take very wide steps, wobbling back and forth,” says senior author Jeremy DeSilva, an associate professor of anthropology. “They are unable to walk with a gait similar to that of the site A footprints, as their hip musculature and knee shape does not permit that kind of motion and balance.”

Bear heels taper and their toes and feet are fan-like, while early human feet are squared off and have a prominent big toe, according to the researchers. Curiously, though, the site A footprints record a hominin crossing one leg over the other as it walked—a gait called “cross-stepping.”

“Although humans don’t typically cross-step, this motion can occur when one is trying to reestablish their balance,” says McNutt. “The site A footprints may have been the result of a hominin walking across an area that was an unlevel surface.”

Based on footprints collected from semi-wild chimpanzees at Ngamba Island Chimpanzee Sanctuary in Uganda and two captive juveniles at Stony Brook University, the team found that chimpanzees have relatively narrow heels compared to their forefoot, a trait shared with bears. But the Laetoli footprints, including those at site A, have wide heels relative to their forefoot.

The site A footprints also contained the impressions of a big toe and second digit. The size difference between the two digits was similar to humans and chimpanzees, but not black bears. These details further demonstrate that the footprints were likely made by a hominin moving on two legs. But comparing the Laetoli footprints at site A and the inferred foot proportions, morphology, and likely gait revealed that the site A footprints are distinct from those of Australopithecus afarensis at sites G and S.

“Through this research, we now have conclusive evidence from the site A footprints that there were different hominin species walking bipedally on 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 1976. It just took the rediscovery of these wonderful footprints and a more detailed analysis to get us here.”

Dartmouth College

Banner
Related Post

Archaeologists find 4 Umayyad epigraphs in the ancient city Knidos

24 May 2022

24 May 2022

Archaeological excavations in the ancient city of Knidos connected to Datça District of Muğla province in western Turkey have unearthed...

2,000-Year-Old Dancing Man Statuette Unearthed in Siberia

6 May 2021

6 May 2021

During excavations for a new bridge over the Ob River in Novosibirsk, Russia’s third-largest district, a ten-centimeter-tall figurine was discovered....

A Chapel was Found Under the Madonna Tal-Hniena Church in Qrendi, Malta

21 May 2021

21 May 2021

Underneath the Madonna Tal-Hniena church in the village of Qrendi in the south of Malta, the remains of an ancient...

4,000-year-old settlement found during Balasore town India

9 July 2021

9 July 2021

A 4,000-year-old settlement and ancient artifacts have been discovered in the Balasore district, India. The Odisha Institute for Maritime and...

Archaeologists have discovered the ruins of what may be one of the four lost Ancient Egyptian “Sun Temples”

31 July 2022

31 July 2022

A Polish and Italian archaeological mission, while conducting an excavation in the Abusir necropolis near Saqqara in Egypt, unearthed the...

Unprecedented 1800-year-old marble bathtub recovered in Turkey

23 April 2022

23 April 2022

The 1800-year-old marble bathtub, which was seized when it was about to be sold by historical artifact smugglers in Aydın’s...

Remains of first Islamic madrassa found in Turkey’s Harran

1 December 2021

1 December 2021

The remnants of a 12th-century madrassa (Islamic institution of higher instruction) have been discovered in the archaeological site of Harran,...

Return of a 4,250-year-old Hattian golden beak-spouted ewer to Turkey

27 October 2021

27 October 2021

The 4,250-year-old golden beak-spouted ewer was returned to the Anatolian Civilizations Museum by the Gilbert Art Foundation. Culture and Tourism...

Largest Anglo-Saxon cemetery discovered in Britain illuminates ‘Dark Ages’

16 June 2022

16 June 2022

Archaeologists working on HS2 (the purpose-built high-speed railway line) have discovered a rich Anglo-Saxon cemetery in Wendover, Buckinghamshire, where almost...

Archaeologists discover Ice Age human footprints in the Utah desert —may be more than 12,000 years old.

26 July 2022

26 July 2022

Daron Duke and Thomas Urban, a Research Scientist with Cornell University, discovered 88 preserved human footprints on alkaline plains at...

A Roman sarcophagus containing two skeletons was found in Bath, England

29 June 2021

29 June 2021

Stone walls, a Roman sarcophagus, and a cremation burial have been unearthed in a renovation project at the Bathwick Roman...

1,500-year-old feast mosaic found in Turkey

2 February 2022

2 February 2022

A 50-square-meter mosaic depicting an open-air feast dating back 1,500 years ago was unearthed during excavations in the ancient city...

“Unprecedented” Phoenician necropolis found in southern Spain

28 April 2022

28 April 2022

A 4th or 5th-century B.C Phoenician necropolis has been found at Osuna in Southern Spain. A well-preserved underground limestone vault...

Ruins of China’s earliest state academy found in east China

21 February 2022

21 February 2022

The ruins of ancient China‘s first government-run institution of higher learning, built in 374 BC, have been discovered in the...

1,300-year-old shipwreck found in southwest France

19 June 2022

19 June 2022

Archeologists in France have discovered the wreck of a ship that navigated the Garonne river in southwestern France in the...

Comments
Leave a Reply

Your email address will not be published. Required fields are marked *