Sankararaman, S., Patterson, N., Li, H., Pääbo, S., Reich, D., 2012. PLoS Genet 8, e1002947.
The authors use the extent of linkage disequilibrium (the association between two or more loci – the distance of DNA that hasn’t been broken up by recombination, which is reduced over time) in modern humans to test between two models (i) Neanderthal (or their close kin)-AMH interbreeding (Neanderthal gene flow) versus (ii) ancient sub-structuring in the ancestral population in Africa. They find evidence for the former and date the last gene flow from Neanderthals to AMH to 37-986kyaBP. Taking the possibility of both ancient sub-structuring and gene flow into account yields dates of 47-65kya.