In 1994 Thomas was one of the first people to read the DNA sequence of the extinct woolly mammoth[4] and in 1998 he coauthored a paper providing genetic support to the claim of recent patrilineal common ancestry among the Jewish priestly caste known as Kohanim (singular "Kohen", "Cohen", or Kohane).
[6] This result proved unpalatable for many archaeologists and led to Thomas developing the "apartheid-like social structure" model[7] to explain the discrepancy between archaeological and genetic estimates of the scale of Anglo-Saxon migration.
[8] 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.
[10] In 2009 – in collaboration with Prof Stephen Shennan and Dr Adam Powell – Thomas published a study in the journal Science showing that population density and or migratory activity are likely to be a major determinants in the maintenance or loss of culturally inherited skills, and that this seemed to explain a number of curious features of the appearance of behavioural modernity in humans at different times in different parts of the world.
This project (titled 'COREX: From correlations to explanations: towards a new European prehistory') will study human biological and cultural evolution from the Neolithic to the Bronze Age through a combination of genomic, archaeological, environmental and isotopic datasets.