Vertebrates Had The Tools For Walking Long Before They Crawled Out Of The Ancient Oceans

Scientists say that the very first vertebrates that walked our planet probably did so in the depths of the oceans millions of years before they moved to land. In 2018, scientists discovered that the little skate fish and some basil sharks were able to essentially walk across the ocean's bottom using some of the same neural circuits that we use for walking today. It was commonly believed that vertebrates only learned to walk when they began to leave the sea for the land about 380 million years ago.

However, new research models based on the little skate fish, one of the most primitive vertebrates, show a much older origin for some of the walking mechanics that could be more than 400 billion years old. Researchers used published video data on the scuttling dynamics of the little skate fish, and mathematicians developed a model to investigate how early leg-like motions could've evolved in the deep-sea.

The model created by the mathematicians is very simple and predicted the most efficient, controlled, and balanced type of walking in a neutrally buoyant environment. The model found the best results required a left foot-right foot alternating pattern similar to how the little skate fish moves. Researchers also found that the little skate fish's motions didn't require any extra energy cost and could be reinforced over time with a simple learning scheme.

Ultimately, the researcher's model led to the understanding that despite a vast range of gaits that could be used, the left-right alternating bipedal control strategy can and will be discovered and the optimal solution for energy efficiency and locomotion. Researchers also note that only rudimentary legs would be needed to achieve the pattern of placement. Once the feet-like fins evolved, the creatures would've needed only minimal neuronal control to achieve walking on land.