Life on Earth didn’t start off on land. It first originated in aquatic environments, and then about 390 million years ago some fish-like ancestors began to venture to the surface and onto the ground itself. They somehow developed the anatomy that enabled them to explore terrestrial environments. However, it is still not known what evolutionary pressures triggered this water-to-land transition.

To understand one of the great transitions in Earth’s history — the moment when aquatic creatures first ventured onto land — researchers at the University of Cambridge have turned to both fossil data and robotics. In their new study, they used paleo-inspired robot designs to explore the potential anatomical and evolutionary changes that enabled fish to walk on land for the first time.

“Paleo-inspired robots are robots inspired by extinct species, generally through the use of data collected from fossils. We’re interested in exploring many species further, but currently, we’re focused on Tiktaalik roseae from the Devonian period, which researchers believe was one of the early fish capable of walking on land,” Michael Ishida, lead study author, and a postdoc researcher at Cambridge, told ZME Science.

The Quest to Understand the Water-to-Land Transition

Scientists have long been fascinated by how ancient fish like Tiktaalik evolved the structures needed to walk on land. However, with fossil evidence often fragmentary, researchers are left guessing how specific bones connected or how these creatures actually moved.

“There are limits to what we can learn from fossils alone,” Ishida notes. 

On the other hand, paleo-robots give scientists the opportunity to physically reconstruct an extinct animal, and understand the alignment, structure, and movement of its different body parts in real-world settings. While building these robots from scratch, scientists sometimes are also able to learn, imagine, and reconstruct parts missing from the fossil record. 

“Paleo-robots can be used to explore ideas about features that may be in the fossil record but yet to be found, features that are completely infeasible, or future features that might emerge from current evolutionary pressures,” Ishida said.

Although the authors plan to use their T. roseae-inspired robot to study the transition from water to land, they suggest there is much more that can be explored using such paleo-robots. For instance, these robots can also be used to study many of the great transitions in the history of life, such as the transition between quadrupedal and bipedal locomotion, terrestrial and avian locomotion, or terrestrial to arboreal locomotion. Fossil records and computer models alone can never reveal such a vast pool of valuable information.

The Making of a Paleo-robot

The ancient fish-inspired robot that Ishida and his team are currently working on will have realistic anatomy and physical movements. It will have mechanical joints, muscles, and ligaments similar to those found in T. roseae fossils.

“One potential experiment is to build a robot with similar anatomy to the extinct animal and to collect data about the energy it uses during its walking gait or the forces it exerts against the ground during specific motions. This data can help confirm or challenge existing theories about how these early animals evolved,” Ishida told ZME Science.

They are also trying to incorporate some features of the modern-day mudskipper into their design. Researchers believe that the mudskipper, a fish that can move on land using its fins, is related to T. roseae. So, it can hopefully help them fill the gaps in the fossils.

To create and put all the bio-inspired parts of the paleo robot together, they plan to use multiple technologies. For example, they suggest that manufacturing methods like 3D printing can help them make replicas of specific fossil specimens. Then, motors pulling cables can be used like artificial muscles, and materials like silicone or urethane (a type of polymer) can be used as the soft connective tissues. The study authors hope to build a fully functional paleo-robot within a few years. 

“Through our work, we hope to motivate more researchers to move into this subfield of research and to start collaborations between paleontologists, biologists, and roboticists to answer questions that no field can address alone,” Ishida concluded.

The study is published in the journal Science Robotics.