Oxford Mathematics Professor Mason Porter and former postdoctoral student Sang Hoon Lee, now of Sungkyunkwan University in Korea, have found a new way of analysing population mix. In the past patterns in human movement have been studied using traffic data, mobile phone records, and even dollar bill circulation. Their new investigation uses centuries-old Korean family books, called jokbos (족보 in Korean), as a record of emigration by female brides. The analysis of this movement, as well as more recent census data, shows that both diffusion- and convection-like phenomena may play a role in mixing different populations.