A team of researchers, led by UC Berkeley doctoral student Benjamin McInroe, published a study in the journal Science revealing that tails were necessary in the transition of animals from an aquatic to terrestrial environment.

The research team used three complementary approaches in its analysis of the role of tails in locomotion, including studying the mudskipper fish because of its similarity to early terrestrial animals. The team then used a physical robot model to measure the amount of drag objects experienced on sandy slopes as well as a mathematical model with geometric mechanics, concluding that tails assisted in the passage of primitive animals to land.

The team’s robot was intentionally simplistic, with two flippers and a tail emulating that of a mudskipper. The robot’s design allowed the team to analyze its movements and locomotion through different terrains, according to McInroe.

“The big idea ends up being that without a tail on slopes, you’re in trouble,” said Daniel Goldman, the study’s senior author and a Georgia Tech associate physics professor. “Using the tail allows you to make progress.”

Prior to the study, researchers had always predicted that the tails of early tetrapods — four-limbed vertebrates — were used only for swimming. McInroe said the team’s research had initially been centered on the mechanics of early locomotion in general and added that he was surprised tails became the main focus of the study.

“This is a very exciting new hypothesis in evolutionary biology that has never really been looked at before,” McInroe said. “We have all the fossils that tell us what (early animals) look like, but that doesn’t really tell us how they moved.”

After studying the robotic model, the team created a mathematical model using geometric mathematics to further understand how a robotic mudskipper could move up sandy slopes. These mathematical results further confirmed that using the tail was the most efficient method of movement.

McInroe said he plans to study other kinds of motion during his time on campus and noted that there is a lot left to study, even with just the robotic model that his team built.

“(What is) particularly interesting is that the tail seems to be acting as a support to help forward motion,” said Ronald Fearing, a UC Berkeley professor of electrical engineering and computer sciences, in an email. “Locomotion on slopes is challenging, and any extra support which can be provided — even by a basic tail function — is going to help animals or robots move better.”

McInroe said that despite scientist’s inability to exactly recreate primitive life, building robotic models allows them to realize how these organisms moved around.

“We don’t have Jurassic Park just yet, but this is the closest thing to it,” McInroe said.

Contact Cassie Ippaso at [email protected] and follow her on Twitter @cassippaso.