The Mesolithic-to-Neolithic transition which coincided with rising sea levels, marked the time when a hunter-gatherer economy gave way to agriculture. Bouldnor Cliff is a submarine archaeological site with a well-preserved Mesolithic palaeosol dated to 8000 years BP. We analyze a core obtained from sealed sediments, combining evidence from microgeomorphology and microfossils with sedimentary ancient DNA (sedaDNA) analyses to reconstruct floral and faunal changes during occupation of this site, before it was submerged. In agreement with palynological analyses, the sedaDNA sequences suggest a mixed habitat of oak forest and herbaceous plants.However, in later sediments, they also provide evidence of wheat 2000 years earlier than expected. These results suggest that sophisticated social networks linked the Neolithic front in southern Europe to the Mesolithic peoples of northern Europe.The Mesolithic-to-Neolithic transition is associated with the replacement of a huntergatherer economy by arable farming of crops such as einkorn, emmer and barley.Although it is generally accepted that the Neolithic had arrived by 6000 years BP on the British mainland, controversy surrounds the timing and mode of Neolithisation in and MS-08 9 , Fig. S2). The sediment layers were of low porosity, with the palaeosol and peat layers sealed beneath dense, silty-clay marine alluvial sediments. We found a sharp boundary between the palaeosol and overlying peat, with no evidence of mixing of particles. Diatom and foraminifera analysis revealed a range of species in the superficial marine alluvial sediments. However, these did not penetrate into the underlying peat layer, indicating a lack of vertical movement in the sediment column.Given the absence of evidence of soil erosion (as might be revealed by illuviation or podsolization), we concluded that archaeological artefacts had been deposited in situ on a pristine land surface rather than entered the samples through alluvial deposition from another site. Radiocarbon dates obtained from 21 samples of wood and plant macrofossils from the sediment cores 9 (Table S1, Fig. S1, Fig. S2) allow an inference of marine inundation beginning 8020-7980 years cal BP, which represents the latest date for human activity at the site, with inundation complete by 7990-7900 years cal BP.We took four palaeosol sediment samples (S308 0-2cm, S308 2-4cm, S308 4-6cm and S308 6-8cm) from a location at the site associated with Mesolithic food debris (burnt hazelnut shells) 9 . The samples were taken at successive 2cm intervals from the top of the stratum, each roughly representing the period of a decade. Samples were taken on site 15 , examined for macrofossils and subjected to ancient DNA extraction in a dedicated laboratory 16 . Samples were found to be devoid of macrofossils, apart from a few Alnus glutinosa (common alder) twigs.We made Illumina libraries from the sediment cores and generated 71,856,199 256-bp single-end reads on the MiSeq platform (Table S2) (Table S3), were performed under high-strin...