IMAGE © SCIENCE/AAAS
Woody plants make up some today’s most impressive and diverse flora, but when and how they evolved is largely unknown. Now, two relatively small fossils provide new clues, and suggest that wood evolved at least 10 million years earlier than previously documented, according to a study published today (August 11) in Science. The fossils, a 407-million-year-old specimen from France and a 397-year-old specimen from Canada, have rings of cells that radiate outward—a defining characteristic of wood—and the walls of their cortexes are thick. Taken together with their surprisingly small size—stems measuring only about 12 centimeters in length—the fossils may help settle a debate about why wood evolved in the first place, suggesting that rather than providing mechanical support for plants as they grew larger, the woody structures served as a plumbing system for taking up water. The large size of woody plants may have then evolved secondarily, taking advantage of the newly evolved support system, ScienceNOW reports.