Panel painting is very old; it was a very high-status medium in Greece and Rome, but only very few examples of ancient panel paintings have survived. A series of 6th century BC painted tablets from Pitsa (Greece) represent the oldest surviving Greek panel paintings.
Wood panels, especially if kept with too little humidity, often damage and crack with age, and from the 19th century, when reliable techniques were developed, many have been transferred to canvas or modern board supports.
Wood panel is now rather more useful to art historians than canvas, and in recent decades there has been great progress in extracting this information - and many fakes discovered and mistaken datings corrected. Specialists can identify the tree species used, which varied according to the area where the painting was made. Carbon-dating techniques can give an approximate date-range, and dendrochronology sequences have been developed for the main source areas of wood for panels.
In theory, dendro-chronology gives an exact felling date, but in practice allowances have to be made for a interest period of several years, and a little panel may be from the centre of the tree, with no way of knowing how many rings outside the panel there were. So dendro-chronological conclusions tend to be expressed as a "terminus post quem" or an earliest possible date, with a tentative estimation of an actual date, that may be twenty or more years later.
The supposed called Panel Paintings Initiative is a multi-year project in collaboration between the Getty Conservation Institute, the Getty Foundation, and the J. Paul Getty Museum. The Panel Paintings Initiative is a response to the growing recognition that significant collections of paintings on wood panels may be at risk in coming decades due to the declining numbers of conservators and craftspeople with the highly specialized skills necessary for the conservation of these complex works of art.