One of the elusive questions in evolutionary biology is when did animals first walk on land? Before this discovery, the fossil record (which includes body fossils and preserved trackways) of the earliest tetrapods dated the water-to-land transition at the Late Devonian period. However, the tetrapod tracks found in Poland suggest that animals first walked the land in the early Middle Devonian period - nearly 20 million years earlier than paleontologists had believed based on early tetrapod body fossils.
The stride length, relative spacing of the footprints, and absence of body drag (which would be seen if the creature was more fish-like), demonstrate that the pathway was made by tetrapod locomotion.
The fossilized footprint has clear impressions of short, triangular toes.
As explained in the video, the trackways clearly belong to a four-legged creature - there are obvious imprints of a walking pattern indicative of an animal with forelimbs and hind limbs. Also, a closer look at the individual footprints reveals the distinct impressions of separate digits (toes) and footpads. This novel discovery is now forcing scientists to reevaluate the timeline of the fish-tetrapod transition and reassess the conditions under which our very distant ancestors moved out of the water and onto land, taking their first steps.
1. Niedźwiedzki G, Szrek P, Narkiewicz K, Narkiewicz M, Ahlberg PE. Tetrapod trackways from the early Middle Devonian period of Poland. Nature. 2010;463(7277):43–48.