Poland's fossil footprints force evolution rethink
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The discovery in southern Poland of 400 million-year-old footprints made by some of the first creatures to walk on land is forcing scientists to re-examine their previous assumptions about evolution.
The fossils – discovered by a team of researchers from Poland and Sweden – show that four-legged vertebrates or tetrapods crawled out of the water and onto land at least 18 million years before scientists previously thought.
"The significance of the findings lies in the fact that they are very old fossils left by animals with four paws and claws in the sediment of a shallow sea and shore," explains Grzegorz Niedźwiedzki, one of the researchers from Warsaw University, who published his findings this month in the prestigious Nature magazine.
Scientists say that the age of footprints found in the Świętokrzyskie mountains means that fish must have begun to morph into land-dwellers much earlier than previously believed. The fact that the rocks in which they were found were packed with marine fossils also came as a surprise. Tetrapods - the precursors of dinosaurs - were until now thought most likely to have developed in freshwater marshes, rather than the sea.
The footprints are 26 centimetres wide, which means the tetrapod was probably around 2.5 metres in length.
Theorists are now asking the questions: What drove the tetrapods out of the water and on to the land? Was it new predators in the sea or lack of oxygen? The discovery in southern Poland could provide some of the answers.
Links
- A video showing the new findings can be seen here: www.nature.com
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