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Researchers recreate 1st steps on dry land

In a groundbreaking study, researchers explored a key evolutionary transition – from animals living in water to living on land – using a robot called MuddyBot.

“MuddyBot,” a robot with a tail. It uses locomotion principles of the mudskipper. Image via Rob Felt (Georgia Tech)/ NSF.

Was a tail needed for ancient vertebrates to make the first steps from water onto dry land? That’s one of the conclusions of a new groundbreaking study, published in the journal Science on July 8, 2016.

The researchers studied this question by observing amphibious fish, then by building a robot they called MuddyBot and watching its movements. Finally, they applied mathematical models of movement to what they learned.

They found that, for the first critical steps out of a watery environment and onto a riverbank or mudflat, stabilizing the body with a tail “provided substantial benefits.”

Meet a mudskipper. Researchers study the motion of mudskippers to understand how early terrestrial animals might have moved about on mud and sand. This animal was photographed at the Georgia Aquarium in Atlanta. Credit: Rob Felt, Georgia Tech

Meet a mudskipper. Image via Georgia Aquarium in Atlanta/ Rob Felt/ NSF.

Study co-author Daniel Goldman, an associate professor in the Georgia Tech School of Physics, said in a statement from the National Science Foundation, which supported the work, that he has:

… long been obsessed with the question of how the first creatures moved onto land.

He and his colleagues – from Georgia Institute of Technology, Carnegie Mellon University, Clemson University and National Institute for Mathematical and Biological Synthesis – explored the behavior and body mechanics of the African mudskipper, an amphibious fish that lives in tidal areas near shore.

Georgia Tech Associate Professor Dan Goldman with the MuddyBot robot in the trackway where its motion was studied. Credit: John Toon, Georgia Tech

Georgia Tech Associate Professor Dan Goldman with the MuddyBot robot in the trackway where scientists studied its motion. Image via John Toon/ Georgia Tech/ NSF

They said the mudskipper is one of a handful of living organisms considered to be potentially close in body structure to the first terrestrial vertebrates, that is, creatures with a backbone including mammals, birds, reptiles, amphibians, and fishes.

Mudskippers are known to use their front fins and tail to move on land with a “crutching” motion. The researchers studied their motion in detail, recording the movements of mudskippers in a lab in a recreated environment they tried to make as similar as possible to ancient riverbanks, where early land-dwellers might have emerged. Goldman said:

We found when mudskippers are using their tail on a sufficiently inclined sandy slope they do pretty well and when they don’t, they don’t do well.

Next, the researchers developed a simplified, mudskipper-like version of a robot, which they call MuddyBot. They used MuddyBot to find out which coordinated motions of limb and tail were most effective on granular surfaces of different inclines.

MuddyBot struggles through a sand pit. The

MuddyBot struggling along through a sand pit. The “crutching” motion that propels it forward is similar to how mudskippers walk on land, these researchers found. Image via Georgia Tech/ Clemson University/ Carnegie Mellon/ Popular Science.

Finally, the researchers used a mathematical and engineering method called geometric mechanics to analyze all the possible ways the MuddyBot can move in space and on different surfaces. They said this method helped them:

…determine what types of movement may or may not have allowed the creature to pull itself up onto a sandy or muddy slope.

Their conclusion: the first creatures to move from water to land may have had tails and may have used a crutching motion to move out of the water.

Bottom line: Researchers explored how ancient creatures moved from water to land, in part via a robot called MuddyBot.

Deborah Byrd

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