-Eurasia ∼45–35 ka shows the presence of at least four distinct populations: early Asians and Europeans, as well as populations with ancestry found hardly or not at all in present-day populations.

-Europeans from around 34–15 ka show high internal population structure.

-Approximately 14–7.5 ka, populations across Eurasia shared genetic similarities, suggesting greater interactions between geographically distant populations.

-Ancient modern human genomes support at least two Neanderthal admixture events, one ∼60–50 ka in early ancestors of non-African populations and a second >37 ka related to the Oase 1 individual.

-A gradual decline in archaic ancestry in Europeans dating from ∼37 to 14 ka suggests that purifying selection lowered the amount of Neanderthal ancestry first introduced into ancient modern humans.

The genetic relationship of past modern humans to today’s populations and each other was largely unknown until recently, when advances in ancient DNA sequencing allowed for unprecedented analysis of the genomes of these early people. These ancient genomes reveal new insights into human prehistory not always observed studying present-day populations, including greater details on the genetic diversity, population structure, and gene flow that characterized past human populations, particularly in early Eurasia, as well as increased insight on the relationship between archaic and modern humans. Here, we review genetic studies on ∼45 000- to 7500-year-old individuals associated with mainly preagricultural cultures found in Eurasia, the Americas, and Africa.

Here's a review of past genetic studies of predominately pre-agricultural groups that was published today. Too bad it's behind a paywall though. Nevertheless, here's the highlights, as well as a map from the paper provided by phys.org.