According to the info on the noticeboard, the "Allée Couverte" came first, at 4500 years ago, followed by the "dolmen" just 4000 years ago. This would fit the basic layout of stones, where the dolmenic chamber has been built against the backstone of the allée couverte, but I have to admit, it does seem rather unusual for a dolmenic structure to be more recent than an allée couverte.
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