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A handful of oak-lined water wells built by Europe鈥檚 first farmers have earned the title of the world鈥檚 oldest surviving wooden architecture. Now, one of the earliest of the oak structures has been precision dated using the tree rings in the wood, and it provides evidence that Europe鈥檚 first farmers may also have been keen on recycling.

Trees in temperate latitudes generally gain a ring of new growth each year 鈥� wider ones in good growing seasons, thinner ones in bad. They are visible in cross-sections of the tree and leave a barcode-like pattern of growth through time.

By matching up distinct sections of that pattern on ancient wood samples from a given region, it is possible to create a tree ring record that goes further and further back in time. In some regions, the timeline stretches back thousands of years.

A team led by Michal Rybn铆膷ek at the Mendel University in Brno, Czech Republic, used this method to date the oak wood lining a prehistoric well discovered in 2018 near the Czech town of Ostrov. Doing so confirmed that the structure 鈥� a large wooden crate 2.5 metres wide聽and 1.8 metres tall 鈥� was probably built 7275 years ago

This is when the trees that provided the crate鈥檚 walls were felled, and it means that the well is the oldest wooden structure dated using tree rings.

Surprisingly, at least one of the four vertical corner posts that give the structure its strength came from a tree that was felled more than a decade earlier. Rybn铆膷ek suspects this is because the early farmers recycled wood. They probably took oak posts from an earlier structure and repurposed them when they decided to dig the well and line it with wood.

Those farmers may have had good reason to dig wells: some evidence suggests Europe experienced severe drought and floods at the time. 鈥淲ells are useful both in times of drought and flood, particularly if flood waters are stagnant,鈥� says Penny Bickle at the University of York in the UK.

Bickle says the wells are an important discovery because they provide evidence of Europe鈥檚 first farmers staying put and investing in the land, instead of moving from place to place as the hunter-gatherers who lived in Europe earlier had done.

Although the Ostrov well is now in the running to be the world鈥檚 oldest wooden architectural structure, Rybn铆膷ek says there are reports of wooden wells in Hungary that may be a few centuries older. But their precise age is unclear because Hungary lacks a good tree ring timescale, so the antiquity of the wells there could only be assessed using the less precise method of carbon dating.