 In 2004 he led a study to show that most lactase persistent Africans did not have the same mutation causing it as Europeans.In 2007, in collaboration with Joachim Burger's group in Mainz, Germany, he showed that the genetic variant that causes lactase persistence in most Europeans (-13,910*T) was rare or absent in early farmers from central Europe.In 2009 Thomas led a computer simulation study indicating that lactase persistence started to co-evolve with the culture of dairying in the LBK (Linearbandkeramik) culture.