An article published in the journal “Proceedings of the National Academy of Sciences” describes a research on the timeline of the mainland colonization by plants. A team of researchers led by the British University of Bristol used the molecular clock methodology to compare genetic differences among the various species even in the absence of complete fossils. The conclusion is that plants started colonizing the mainland about 100 million years earlier than previously thought based on the oldest fossils, which date back to about 420 million years ago.