Wood is starting to show its age. Philippe Gerrienne, a researcher in palaeobotany at the University of Liège, discovered two plant fossils that are 407 and 397 million years old respectively and contain traces of wood. The earliest ever brought to light! This discovery has pushed back the emergence of wood on earth by some 10 million years. It also confirms a hypothesis:  it would seem that wood was not made by plants in order to increase their resistance and become trees, but initially to allow improved circulation of water. The results of this research have been published in the journal Science (1).

Most discoveries are made by accident. What if the walker Marcel Ravidat's dog had never rushed into the Lascaux caves? What if Wilhelm Röntgen had never lit up his wife's hand with rays that he named 'x-rays'? What if lab assistant Jim Slatters, whilst developing an aspartam-based ulcer treatment, had not licked his fingers to turn the page of his notebook and marvelled at its sweet taste?

What if Philippe Gerrienne had never sawn into these small pieces of sandstone? Dark, almost black, seemingly insignificant stones. Very different from the fossils with which the palaeobotanist is used to working. 'A French geologist gave me these four stones six or seven years ago at a conference.' He had collected them from the Chateaupanne quarry, near Angers', says the FNRS researcher who is a lecturer at the Geology Department of the University of Liège. 'I left them in a corner, then I almost forgot they were there. '

Until the day a big spring clean appeared necessary... Philippe Gerrienne started to sort out his cupboards and came across these little pieces of stone. He decided to saw into them. Just in case, 'one never knows...’.  The first sections did not reveal anything of interest. He continued to saw. After some time, he noticed a tiny shiny mark, in the middle of the black rock. No bigger than one or two millimetres. Almost invisible to the naked eye. But it did not escape the shrewd eye of Philippe Gerrienne. He had just discovered the oldest trace of wood ever found.

The fossil of this plant (which is yet to be given a name) is 407 million years old. The plant is between ten and twenty centimetres high and its stem - no thicker than a twig - produces 'lateral systems' 120 degrees apart (the ancestors of leaves). At first sight, the similarity with the trees that populate our gardens and forests is far from obvious. Yet… 'Until now the oldest plant containing traces of wood was Aneurophyton, which lived 390 million years ago', he explains. We suspected that there was an even older plant as Aneurophyton was already big: it looked like a little tree. It is something many of the researchers had been wondering about '

(1) Philippe Gerrienne, Patricia G. Gensel, Christine Strullu-Derrien, Hubert Lardeux, Philippe Steemans, Cyrille Prestianni, A Simple Type of Wood in Two Early Devonian Plants, Science 333, 837 (2011)