Ancient Vertebrates may have had equipment for walking long before they left the ocean

The first vertebrates to walk on our planet in the deep ocean may have made millions of years before their relatives later moved to land.

In 2018, scientists were surprised to find the small skate fish (Leucoraja erinacea) and some basal sharks were able to land on the ocean floor using many of the same cloud circuits we use for walking today.

In general, it is thought that spines only learned to walk when they began to flee the sea to the shore, about 380 million years ago. But other models based on the small skate fish – one of the most predominantly invertebrate animals – show a much deeper origin, perhaps more than 400 million years ago.

Using published video data on the scuttling dynamics of this benthic creature, mathematicians have developed a model to study how early foot-like movements can occur in the deep sea.

The simple model they created predicts the most efficient, controlled, and balanced type of walking in a neutral living environment: The best result requires a very similar left-footed walking pattern. to waddle the small skate.

Moreover, this type of trudging does not require additional energy cost and could be reinforced over time using a simple learning scheme.

“In the context of our model, these findings suggest that, despite the large solution space of gates, a left-handed alternating bipedal control strategy is found and is the best solution best for energy-efficient movement, ”the study’s authors write.

Finding a true example of this ancient organism is similar to finding a “needle in a haystack”, the team admits, but they say only basic feet would be needed to achieve this pattern of foot position. After the emergence of these feather-like feathers, the ancient creature then had to gain very little neuronal control over their new and improved limbs.

After four learning events in the model, a one-legged locomotive strategy began to emerge. After 200 incidents, a two-legged walking pattern took over. Before the 600th program, the modified creature began to switch between left and right steps.

Running around 50 learning settings for 5,000 programs, including various learning parameters and rewards, the authors found that the best solution matches the small skate walk in 70 percent of each issue.

This simple control strategy suggests that walking in the deep sea is a strong and effective behavior similar to passive walking, like the slinky toy that “walks” down a slope without the need for complex control, just gravity.

The small skate, of course, is not a completely tolerant skunk. Its brain cells still control six muscles for movement, but the authors state that this system takes advantage of the same principles as a passive man: “Stable locomotive under a constant energy source out of control. “

The authors are not sure why the small skate developed slow walking on the seabed, but they suggest that it is more efficient and cost-effective than swimming at the same speed. Further metabolic studies of the deep-sea creature need to confirm this hypothesis.

In wild times, the small skate uses both legs at the same time to “pound” forward and to start the left-to-right walking pattern. This type of movement was not detected in the model, but the authors believe that it may be preferred when faster acceleration is required and energy efficiency is less important. This unusual pound needs a little more work.

“The combination of a reliable low-gravity environment and body morphology may have helped pave the way for bipedal gears before our aquatic ancestors moved to terra firma,” says University-based applied mathematician Lakshminarayanan Mahadevan Harvard.

“As our ancient ancestors moved to land, the control strategy seemed to become more complex. But in homogeneous homogenous environments, such as the seabed, it may be a simple strategy. that was missing. “

To add to this theoretical model, researchers even built a simple bipedal robot based on similar deep sea conditions. In the end, the behavior of this robot showed things that are very similar to their very good walking model. Its consistent foot pattern requires no extra energy and waves on either side of the body for stability.

The robot, however, tends to walk a little faster than seen in the small skate.

The authors admit that they may not know for sure how the first walking scratch arose, but their model helps to update some of the passive dynamics and cloud cycles seen in it. the living organisms.

“Understanding how the brain, body and environment worked together in heterogeneous aquatic and terrestrial environments required the inclusion of proprioceptive feedback,” the authors recommend.

“But in reliable homogeneous environments, perhaps the simple strategy devised here is where it all started.”

The study was published in the Interface Magazine of the Royal Society.