Tails Helped Early Animals Make the Transition from Sea to Land

A new study just published in Science provides insight into how the first vertebrates on land may have moved through sand and other difficult terrain. The findings, from a study sponsored by the United States Army and the National Science Foundation, also have important implications for robotic locomotion.

Over 360 million years ago, a handful of animals began to make the transition onto land. This was one of the most important events in natural history and it couldn’t have been easy for the first vertebrates to accomplish. In the past, research has focused on the evolution of limbs. The development of legs helped the first land vertebrates get around, allowing them to travel through mud and sand. The researchers of this new study, however, decided to focus on tails.

The research team investigated whether or not tails helped the first land animals transition to terrestrial life. They studied African mudskippers (Periopthalmus barbaratus), a species of fish known for hopping around on the shore. This lifestyle makes mudskippers useful models for studying the locomotion of early terrestrial animals. The researchers used the morphological data from the mudskippers to design mathematical models and simulations. The team also designed a robot, called MuddyBot, to further study how the tail came into play. The robot had two limbs and a tail, designed to mimic the body of a mudskipper.

The team found that the tail was very important for moving around on land. MuddyBot could only climb slopes and move through sand when using its tail. A powerful tail, like the one an actual mudskipper would have, is necessary for dealing with inclines and tough terrain. During the early transitions from water to land, animals gained new features to help them, including limbs. These new findings suggest that an existing body part, the tail, was just as important.

The study provides new insights into how animals first managed to move on land, one of the most major evolutionary events in history. The research is also useful for robotics. Researchers can use the data from this study in order to design more mobile robots, especially ones that need to deal with difficult terrain such as mud.


Daniel I. Goldman et al. Tail use improves soft substrate performance in models of early vertebrate land locomotors. Science (2016).

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