Ferns 1 (IMAGE) University of Southampton Caption Ferns were some of the first land plants to colonise the continents, with some analysis indicating that they evolved about 430 million years ago. The scientists report a step change in the composition of the continental crust at precisely this time, which they relate to fundamental changes in river systems tied to the evolution of land plants. Photograph: Dr Tom Gernon / University of Southampton [@TMGernon]. Credit Photograph: Dr Tom Gernon / University of Southampton [@TMGernon]. Usage Restrictions Photograph: Dr Tom Gernon / University of Southampton [@TMGernon]. License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.