New Analysis of Foot Prints Found at Laetoli!

A new, and exciting announcement coming from Dr. Ellie McNutt and Dr. Jeremy DeSilva et al found in Nature! The following is taken from Prof. DeSilva’s Twitter and explains the findings quite well!

You can access the paper here:

Today, Dr. Ellie McNutt & a large team announced in @nature the discovery of 3.66-million-year-old footprints at Laetoli, Tanzania. These tracks are different from the famous site G trail–evidence of a 2nd species of bipedal hominin at Laetoli!

Footprints at Laetoli were discovered by Mary Leakey’s team in 1976 after Kay Behrensmeyer, Andrew Hill, and others famously had an elephant dung fight. Ultimately 18,400 footprints were documented at site A from different mammals, birds, insects. Image by K. Behrensmeyer.

In September of 1976, Philip Leakey and Peter Jones found 5 consecutive tracks made by a bipedal mammal at site A. Mary Leakey and Dick Hay proposed in the pages of @nature that they were made by a hominin with a “somewhat shambling” gait. Image by J. Reader.

But, the footprints were strangely shaped and, if from a hominin, were from one that was crossing the left foot over the right while walking, like a model on a runway.

In 1978, the famous trackway at site G was discovered by Paul Abell and Ndibo Mbuika. These footprints were clearly hominin. Photo by John Reader

So, what were the strange site A prints? Some wondered if they might have been made by a bipedal bear. Prof. Russ Tuttle found that the trackway and footprints showed some affinities with bears. Dismissed as non-hominin, the site A prints fell into obscurity.

BUT… Tuttle also wrote, “until detailed, naturalistic biometric and kinesiological studies are performed on bipedal bears and barefoot humans, we will have to defer choosing among the hominid and ursid hypotheses on Laetoli individual A.”

And the site A prints were never fully excavated. Tim White and Gen Suwa wrote, “reliable identification of these enigmatic prints at Laetoli site A will be impossible until they are more fully cleaned and followed laterally.”

Up here in the woods of @Dartmouth, we have a lot of bears. Dr. McNutt worked with Dr. Ben Kilham—a black bear expert—and collected footprint data on black bears whose feet were about the same size as the footprint maker at Laetoli site A.

Up here in the woods of @Dartmouth, we have a lot of bears. Dr. McNutt worked with Dr. Ben Kilham—a black bear expert—and collected footprint data on black bears whose feet were about the same size as the footprint maker at Laetoli site A.

Bear heels are narrow, they have fan-shaped toes, and they sometimes leave claw marks. The Laetoli site A prints preserve none of those features.

Plus, bears cannot balance on a single leg easily and wobble back and forth when they walk bipedally, leaving widely spaced prints. Chimpanzees do this, too.

In fact, the easiest way to produce a trackway with one foot directly in front of the other is to have an abductor mechanism and/or valgus knees. These are key characteristics of hominins and hinted to us that the site A prints were not from a bear.

In June 2019, Prof. Charles Musiba @CUDenver led a team to Laetoli to, in part, search for these prints. It is not easy to get to the outcrops.

We were even joined by Joshua Gates from @ExpeditionUNK for a day.

We used Mary Leakey’s maps to measure to the exact spot where the A prints should be (if still preserved), and luckily found the juvenile elephant prints that ran parallel to the bipedal trackway, before Kallisti Fabian uncovered the first print.

Seasonal rains had not washed the prints away. It had pulled enough sediment on top of them to preserve them for forty years. We brushed them clear of matrix, uncovering details that were still obscured in 1977.

The team found the original 5 prints and excavated back into the hillside but could not find any more prints, unfortunately. We plan to return to search for more. Image by Shirley Rubin.

We laser scanned the trackway and took enough photos to do photogrammetry. These were tools unavailable to researchers in the 1970s.

Kevin Hatala worked his magic and showed that the shape of the site A footprints are as different from the prints at sites G and S as a chimpanzee footprint is from a human’s.

And then there is just the eyeball test.

There is growing evidence that multiple hominin species coexisted during the Pliocene of Eastern Africa. The Burtele foot from Woranso-Mille, Ethiopia demonstrates that different kinds of hominins were walking differently from one another at this time, too.

Not only were different hominins coexisting—some of them shared the same landscape. The Laetoli footprint tuff captures a snapshot in time. As the site A hominin was walking north, a group of A. afarensis—2km to the west—were trudging that way, too.

Skeptical of our interpretation? That’s ok. Science is not about belief—we welcome other teams to assess our findings and attempt to replicate our results. That can only happen if fossils/footprints are available for study.

To that end, you can find high-resolution 3d scans of the footprints on morphosource.org. They are great for teaching, too! @Evo_Explorer @WrldOfPaleoAnth

One question that remains for me is what hominin made the site A prints? In our paleoanthropological Cinderella story, what foot will fit the proverbial slipper? There are secrets still hiding in the ancient ash at Laetoli.

Published by sethchagi

I am a Paleoanthropology Student, so far with two degrees, in Anthropology and Human Behavioral Science, pursuing my PhD. I love to read (like a lot) and write, I love my family, and I adore anthropology! Remember, never stop exploring and never stop learning! There is always more to learn!

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