.to_grid                Convert from geographic coordinates in a given
                        projection system to the relative position in
                        rows and columns of a grid.
euro_dates              Coordinates and earliest dates (med cal BP) for
                        European Neolithic sites. Dataset adapted from
                        the supplementary information in Pinhasi et al.
                        2005
                        (https://doi.org/10.1371/journal.pbio.0030410).
euro_npp                Transformed Net Primary Production (NPP) from
                        11 ka to 4 ka at 1000 yr steps. Calculated with
                        the Miami formula using paleoclimatic data from
                        Beyer et al. 2020.
                        (https://doi.org/10.1038/s41597-020-0552-1).
                        Clipped to max=1350, squared and scaled to
                        [0,1].
euro_terr               Reclassified terrain layer with elevation >
                        1750 m as barriers and rivers and coastline as
                        corridors. Terrain reclassified from SRTM.
                        Rivers rasterized from GSHHG
                        (https://www.soest.hawaii.edu/pwessel/gshhg/)
                        and coastline rasterized from rnaturalearth.
ppnb                    Coordinates and earliest dates (med cal BP) for
                        Late Pre-Pottery Neolithic B sites in the Near
                        East. Dataset adapted from the supplementary
                        information in Pinhasi et al. 2005
                        (https://doi.org/10.1371/journal.pbio.0030410).
simulate_dispersal      Simulates first arrival times from one or more
                        origins.
