From A method for genome-wide genealogy estimation for thousands of samples, this section jumped out at me:
In the East and South Asian groups, the data suggest a very recent arrival of Denisovan DNA (mainly <15,000 YBP). In non-Africans, Neanderthal sharing remains high for branches with lower-end age younger than ~30,000 YBP. These dates are only lower bounds on the introgression time, and an accurate arrival date of Neanderthal DNA would require estimating a joint genealogy that requires further work….
Comparing YRI, GBR, BEB (Bengali in Bangladesh) and CHB to expectations under panmixia, we observe a strong excess of mutations on deep branches with lower coalescence age <40,000 YBP in all cases, which is almost entirely explained by Neanderthals/Denisovans in the non-African populations, but not in YRI (Fig. 4d, Methods). In panmictic simulations with matched population size histories, we observed no such excess (Supplementary Fig. 6). This gives evidence for ancient but uncharacterized population structure within Africa, as suggested elsewhere…Figure 4b shows one example consistent with an introgression event in YRI, not involving a closely relative of Neanderthals.
The inference of deep structure within Africa is not a great surprise. But note that their estimate for Denisovan admixture is that on the whole, it could be half as old as Neanderthal admixture. I don’t put much stock in the specific estimate of the date, but rather the relative time.