Figure 1
Association between human migration and trade volumes through time. The green line shows the number of migration events estimated by GLOBETROTTER15 per century. The red line shows the average volume of trade per century adapted from data detailed by Beaujard9. The blue line shows the average distance of migration per century, with light blue shading showing the variance. Dashed vertical lines mark the four trade phases9. Horizontal bars represent t-tests between successive phases with significance values shown for the variance of migration distances (light blue), the average migration distance (dark blue) and the number of migration events (green): **P < 0.01; *P < 0.05; -: not significant.
