The title of The First Stones, a newly published book edited by William Britnell and Alasdair Whittle, proclaims a bold new thesis: that the Neolithic long cairn at Penywyrlod, in the Black Mountains of south-east Wales, is one of the earliest of its kind. With the benefit of 50 new radiocarbon dates, and new ways of modelling those dates using Bayesian analysis, its authors revisit excavations that first took place in the 1970s – and argue that this distinctive monument represents the birth of a new tomb-building tradition, as Chris Catling discovers.