Quirks & Quarks

A robot reconstruction of a 300-million-year-old fossil shows how it walked

Researchers had bones and footprints, and had to make the robot to fit both

Researchers had bones and footprints, and had to make the robot to fit both

Scientists built a robot to see how a 300-million-year-old year old lizard walked (Tomislav Horvat (EPFL Lausanne)/Kamilo Melo (EPFL Lausanne))
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A robot reverse-engineered to walk like one of the earliest land living animals is giving scientists a glimpse into how animals evolved when they moved from water to land.

"We recreated the fossil by building a robot which was able to emulate the gait, the locomotion that we inferred for the fossil," said Dr. John Nyakatura, the lead author and evolutionary biologist at Humbolt University of Berlin.

The fossil

The fossil they were looking at belonged to a four-legged lizard-like creature known as Orobates pabsti, which lived approximately 300 million years ago.

Top view of the fossil the scientists used to to build an Orobates pabsti robot (Thomas Martens (Museum der Natur Gotha))

"We consider Orobates as a key fossil for the understanding of the evolution of land living tetrapods," Nvakatura explained.

This fossil represents the transition between the amphibious lifestyle seen in frogs, which spend a substantial part of their lives in water, and amniotes, prehistoric lizard-like creatures that laid eggs, walked, and lived on dry land.

How scientists reverse-engineered the fossil

In their quest to bring a robotic version of this prehistoric creature to life, the scientists had some great information to go by: not only did they have the Orobates fossil, but they also had its fossilized tracks.

"This was a great starting point for us to actually understand how these animals back then walked and behaved," said Nyakatura.

Trackways of Ichnotherium sphaerodactylum assigned to Orobates pabsti as track-maker (Sebastian Voigt (Urweltmuseum Geoskop Thallichtenberg))

From the tracks, they were able to understand important aspects of the animal's gait, such as how long and wide its step was, as well as the rotation of its feet as it walked.  

They simulated a digital version of the fossil using CT scans, which they animated to explore different anatomical possibilities as they made the fossil walk within its tracks. They looked at things like whether its bones were colliding or its joints were working properly.

The next simulation they put their digital and robotic fossil creations through tested for things like the effects of gravity and friction, which also influence locomotion.

Insights into how early land animals walked

This helped them arrive at its mostly likely gait, which they programmed into the robot. Nyakatura said when the robot first started walking, it was a "magical moment" for him and his team.

They discovered that Orobates moved in a more advanced way than its amphibian-like predecessors. It was able to lift its belly off the ground when it walked, which made for more efficient locomotion—somewhat similar to a modern crocodile.

"The locomotion was suggesting that this animal already was quite independent from water."

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