When you look at an African lungfish, you see an aquatic animal with an eel-like body and what appear to be small, scrawny limbs, which are actually pelvic fins.
A new study suggests this creature could up-end what we thought we knew about the evolution of life on Earth as it made its way from water to land.
After extensive video analysis, University of Chicago researchers found the African Lungfish uses its pelvic fins to lift itself off the surface and propel itself forward. Before now, scientists believed these abilities originated in the early species of tetrapods – creatures with four feet who appeared on Earth later than the lungfish’s ancestors.
The researchers think their observations will reshuffle our understanding of the order of evolutionary events that led up to creatures adapting to life on land. Fossil tracks thought to be the work of early tetrapods species could have instead been produced by lobe-finned ancestors of the lungfish.
The study’s lead author, graduate student Heather King, and her colleagues designed and built a special tank to study and videotape the lungfish from the side and below for in-depth analysis. They chose to videotape and observe the lungfish in action, because if they only looked at the bones, as one would with a fossil, it might not be apparent the animals could have the ability of locomotion.
The researchers reported the lungfish demonstrated both “bounding” motions, where both limbs moved at the same time, and “walking,” with the fish alternating use of its limbs to move forward.
These behaviors, along with the ability to fully rotate its limb and to place each subsequent footfall in front of the joint, suggest to researchers that similar creatures, perhaps ancestors of the lungfish, would have been capable of producing some of the fossil tracks credited to tetrapods.
The group says its discovery suggests that many of the developments necessary for animals to make the transition from water to land may have taken place long before early tetrapods were able to take their first steps on land.
They believe the lobe-finned ancestors of the lungfish, as well as tetrapods, could be responsible for the evolution of hind-limb propulsion and the ability to walk at the bottom of a lake or marsh millions of years before the appearance of land-dwelling animals.